## conversion

conversion — convert images in some way: change band format, change header, insert, extract, join

## Stability Level

Stable, unless otherwise indicated

## Functions

int | vips_copy ()
int | vips_tilecache ()
int | vips_linecache ()
int | vips_sequential ()
int | vips_cache ()
int | vips_copy_file ()
int | vips_embed ()
int | vips_gravity ()
int | vips_flip ()
int | vips_insert ()
int | vips_join ()
int | vips_arrayjoin ()
int | vips_extract_area ()
int | vips_crop ()
int | vips_smartcrop ()
int | vips_extract_band ()
int | vips_replicate ()
int | vips_grid ()
int | vips_transpose3d ()
int | vips_wrap ()
int | vips_rot ()
int | vips_rot90 ()
int | vips_rot180 ()
int | vips_rot270 ()
int | vips_rot45 ()
VipsAngle | vips_autorot_get_angle ()
void | vips_autorot_remove_angle ()
int | vips_autorot ()
int | vips_zoom ()
int | vips_subsample ()
int | vips_cast ()
int | vips_cast_uchar ()
int | vips_cast_char ()
int | vips_cast_ushort ()
int | vips_cast_short ()
int | vips_cast_uint ()
int | vips_cast_int ()
int | vips_cast_float ()
int | vips_cast_double ()
int | vips_cast_complex ()
int | vips_cast_dpcomplex ()
int | vips_scale ()
int | vips_msb ()
int | vips_byteswap ()
int | vips_bandjoin ()
int | vips_bandjoin2 ()
int | vips_bandjoin_const ()
int | vips_bandjoin_const1 ()
int | vips_bandrank ()
int | vips_bandfold ()
int | vips_bandunfold ()
int | vips_bandbool ()
int | vips_bandand ()
int | vips_bandor ()
int | vips_bandeor ()
int | vips_bandmean ()
int | vips_recomb ()
int | vips_ifthenelse ()
int | vips_switch ()
int | vips_flatten ()
int | vips_addalpha ()
int | vips_premultiply ()
int | vips_unpremultiply ()
int | vips_composite ()
int | vips_composite2 ()
int | vips_falsecolour ()
int | vips_gamma ()

## Types and Values

enum | VipsExtend
enum | VipsCompassDirection
enum | VipsDirection
enum | VipsAlign
enum | VipsAngle
enum | VipsAngle45
enum | VipsInteresting
enum | VipsBlendMode

## Includes

    #include <vips/vips.h>

## Description

These operations convert an image in some way. They can be split into a two main groups.

The first set of operations change an image's format in some way. You can change the band format (for example, cast to 32-bit unsigned int), form complex images from real images, convert images to matrices and back, change header fields, and a few others.

The second group move pixels about in some way. You can flip, rotate, extract, insert and join pairs of images in various ways.

## Functions

### vips_copy ()

    int
    vips_copy (VipsImage *in,
               VipsImage **out,
               ...);

Optional arguments:

- `width` : `gint`, set image width

- `height` : `gint`, set image height

- `bands` : `gint`, set image bands

- `format` : VipsBandFormat, set image format

- `coding` : VipsCoding, set image coding

- `interpretation` : VipsInterpretation, set image interpretation

- `xres` : `gdouble`, set image xres

- `yres` : `gdouble`, set image yres

- `xoffset` : `gint`, set image xoffset

- `yoffset` : `gint`, set image yoffset

Copy an image, optionally modifying the header. VIPS copies images by copying pointers, so this operation is instant, even for very large images.

You can optionally change any or all header fields during the copy. You can make any change which does not change the size of a pel, so for example you can turn a 4-band uchar image into a 2-band ushort image, but you cannot change a 100 x 100 RGB image into a 300 x 100 mono image.

See also: `vips_byteswap()`, `vips_bandfold()`, `vips_bandunfold()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_tilecache ()

    int
    vips_tilecache (VipsImage *in,
                    VipsImage **out,
                    ...);

Optional arguments:

- `tile_width` : width of tiles in cache

- `tile_height` : height of tiles in cache

- `max_tiles` : maximum number of tiles to cache

- `access` : hint expected access pattern VipsAccess

- `threaded` : allow many threads

- `persistent` : don't drop cache at end of computation

This operation behaves rather like `vips_copy()` between images `in` and `out` , except that it keeps a cache of computed pixels. This cache is made of up to `max_tiles` tiles (a value of -1 means any number of tiles), and each tile is of size `tile_width` by `tile_height` pixels.

Each cache tile is made with a single call to `vips_region_prepare()`.

When the cache fills, a tile is chosen for reuse. If `access` is VIPS_ACCESS_RANDOM, then the least-recently-used tile is reused. If `access` is VIPS_ACCESS_SEQUENTIAL the top-most tile is reused.

By default, `tile_width` and `tile_height` are 128 pixels, and the operation will cache up to 1,000 tiles. `access` defaults to VIPS_ACCESS_RANDOM.

Normally, only a single thread at once is allowed to calculate tiles. If you set `threaded` to `TRUE`, `vips_tilecache()` will allow many threads to calculate tiles at once, and share the cache between them.

Normally the cache is dropped when computation finishes. Set `persistent` to `TRUE` to keep the cache between computations.

See also: `vips_cache()`, `vips_linecache()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_linecache ()

    int
    vips_linecache (VipsImage *in,
                    VipsImage **out,
                    ...);

Optional arguments:

- `access` : hint expected access pattern VipsAccess

- `tile_height` : height of tiles in cache

- `threaded` : allow many threads

This operation behaves rather like `vips_copy()` between images `in` and `out` , except that it keeps a cache of computed scanlines.

The number of lines cached is enough for a small amount of non-local access.

Each cache tile is made with a single call to `vips_region_prepare()`.

When the cache fills, a tile is chosen for reuse. If `access` is VIPS_ACCESS_RANDOM, then the least-recently-used tile is reused. If `access` is VIPS_ACCESS_SEQUENTIAL, then the top-most tile is reused. `access` defaults to VIPS_ACCESS_RANDOM.

`tile_height` can be used to set the size of the strips that `vips_linecache()` uses. The default is 1 (a single scanline).

Normally, only a single thread at once is allowed to calculate tiles. If you set `threaded` to `TRUE`, `vips_linecache()` will allow many threads to calculate tiles at once and share the cache between them.

See also: `vips_cache()`, `vips_tilecache()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_sequential ()

    int
    vips_sequential (VipsImage *in,
                     VipsImage **out,
                     ...);

Optional arguments:

- `strip_height` : height of cache strips

This operation behaves rather like `vips_copy()` between images `in` and `out` , except that it checks that pixels on `in` are only requested top-to-bottom. This operation is useful for loading file formats which are strictly top-to-bottom, like PNG.

`strip_height` can be used to set the size of the tiles that `vips_sequential()` uses. The default value is 1.

See also: `vips_cache()`, `vips_linecache()`, `vips_tilecache()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_cache ()

    int
    vips_cache (VipsImage *in,
                VipsImage **out,
                ...);

Optional arguments:

- `tile_width` : width of tiles in cache

- `tile_height` : height of tiles in cache

- `max_tiles` : maximum number of tiles to cache

This operation behaves rather like `vips_copy()` between images `in` and `out` , except that it keeps a cache of computed pixels. This cache is made of up to `max_tiles` tiles (a value of -1 means any number of tiles), and each tile is of size `tile_width` by `tile_height` pixels. By default it will cache 250 128 x 128 pixel tiles, enough for two 1920 x 1080 images.

This operation is a thin wrapper over `vips_sink_screen()`, see the documentation for that operation for details.

It uses a set of background threads to calculate pixels and the various active cache operations coordinate so as not to overwhelm your system. When a request is made for an area of pixels, the operation will block until all of those pixels have been calculated. Pixels are calculated with a set of threads.

See also: `vips_tilecache()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_copy_file ()

    int
    vips_copy_file (VipsImage *in,
                    VipsImage **out,
                    ...);

A simple convenience function to copy an image to a file, then copy again to output. If the image is already a file, just copy straight through.

The file is allocated with `vips_image_new_temp_file()`. The file is automatically deleted when `out` is closed.

See also: `vips_copy()`, `vips_image_new_temp_file()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_embed ()

    int
    vips_embed (VipsImage *in,
                VipsImage **out,
                int x,
                int y,
                int width,
                int height,
                ...);

Optional arguments:

- `extend` : VipsExtend to generate the edge pixels (default: black)

- `background` : VipsArrayDouble colour for edge pixels

The opposite of `vips_extract_area()`: embed `in` within an image of size `width` by `height` at position `x` , `y` .

`extend` controls what appears in the new pels, see VipsExtend.

See also: `vips_extract_area()`, `vips_insert()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
x | place `in` at this x position in `out` |
y | place `in` at this y position in `out` |
width | `out` should be this many pixels across |
height | `out` should be this many pixels down |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_gravity ()

    int
    vips_gravity (VipsImage *in,
                  VipsImage **out,
                  VipsCompassDirection direction,
                  int width,
                  int height,
                  ...);

Optional arguments:

- `extend` : VipsExtend to generate the edge pixels (default: black)

- `background` : VipsArrayDouble colour for edge pixels

The opposite of `vips_extract_area()`: place `in` within an image of size `width` by `height` at a certain gravity.

`extend` controls what appears in the new pels, see VipsExtend.

See also: `vips_extract_area()`, `vips_insert()`.

#### Parameters

in | input image |
out | output image |
direction | place `in` at this direction in `out` |
width | `out` should be this many pixels across |
height | `out` should be this many pixels down |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_flip ()

    int
    vips_flip (VipsImage *in,
               VipsImage **out,
               VipsDirection direction,
               ...);

Flips an image left-right or up-down.

See also: `vips_rot()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
direction | flip horizontally or vertically |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_insert ()

    int
    vips_insert (VipsImage *main,
                 VipsImage *sub,
                 VipsImage **out,
                 int x,
                 int y,
                 ...);

Optional arguments:

- `expand` : expand output to hold whole of both images

- `background` : colour for new pixels

Insert `sub` into `main` at position `x` , `y` .

Normally `out` shows the whole of `main` . If `expand` is TRUE then `out` is made large enough to hold all of `main` and `sub` . Any areas of `out` not coming from either `main` or `sub` are set to `background` (default 0).

If `sub` overlaps `main` , `sub` will appear on top of `main` .

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in

arithmetic).

See also: `vips_join()`, `vips_embed()`, `vips_extract_area()`.

[method]

#### Parameters

main | big image |
sub | small image |
out | output image. | [out]
x | left position of `sub` |
y | top position of `sub` |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_join ()

    int
    vips_join (VipsImage *in1,
               VipsImage *in2,
               VipsImage **out,
               VipsDirection direction,
               ...);

Optional arguments:

- `expand` : `TRUE` to expand the output image to hold all of the input pixels

- `shim` : space between images, in pixels

- `background` : background ink colour

- `align` : low, centre or high alignment

Join `in1` and `in2` together, left-right or up-down depending on the value of `direction` .

If one is taller or wider than the other, `out` will be has high as the smaller. If `expand` is `TRUE`, then the output will be expanded to contain all of the input pixels.

Use `align` to set the edge that the images align on. By default, they align on the edge with the lower value coordinate.

Use `background` to set the colour of any pixels in `out` which are not present in either `in1` or `in2` .

Use `shim` to set the spacing between the images. By default this is 0.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in

arithmetic).

If you are going to be joining many thousands of images in a regular grid, `vips_arrayjoin()` is a better choice.

See also: `vips_arrayjoin()`, `vips_insert()`.

#### Parameters

in1 | first input image |
in2 | second input image |
out | output image. | [out]
direction | join horizontally or vertically |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_arrayjoin ()

    int
    vips_arrayjoin (VipsImage **in,
                    VipsImage **out,
                    int n,
                    ...);

Optional arguments:

- `across` : `gint`, number of images per row

- `shim` : `gint`, space between images, in pixels

- `background` : VipsArrayDouble, background ink colour

- `halign` : VipsAlign, low, centre or high alignment

- `valign` : VipsAlign, low, centre or high alignment

- `hspacing` : `gint`, horizontal distance between images

- `vspacing` : `gint`, vertical distance between images

Lay out the images in `in` in a grid. The grid is `across` images across and however high is necessary to use up all of `in` . Images are set down left-to-right and top-to-bottom. `across` defaults to `n` .

Each input image is placed with a box of size `hspacing` by `vspacing` pixels and cropped. These default to the largest width and largest height of the input images.

Space between images is filled with `background` . This defaults to 0 (black).

Images are positioned within their `hspacing` by `vspacing` box at low, centre or high coordinate values, controlled by `halign` and `valign` . These default to left-top.

Boxes are joined and separated by `shim` pixels. This defaults to 0.

If the number of bands in the input images differs, all but one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the n-band images are operated upon.

The input images are cast up to the smallest common type (see table Smallest common format in

arithmetic).

See also: `vips_join()`, `vips_insert()`.

#### Parameters

in | array of input images. | [array length=n][transfer none]
out | output image. | [out]
n | number of input images |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_extract_area ()

    int
    vips_extract_area (VipsImage *in,
                       VipsImage **out,
                       int left,
                       int top,
                       int width,
                       int height,
                       ...);

Extract an area from an image. The area must fit within `in` .

See also: `vips_extract_bands()`, `vips_smartcrop()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
left | left edge of area to extract |
top | top edge of area to extract |
width | width of area to extract |
height | height of area to extract |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_crop ()

    int
    vips_crop (VipsImage *in,
               VipsImage **out,
               int left,
               int top,
               int width,
               int height,
               ...);

A synonym for `vips_extract_area()`.

See also: `vips_extract_bands()`, `vips_smartcrop()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
left | left edge of area to extract |
top | top edge of area to extract |
width | width of area to extract |
height | height of area to extract |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_smartcrop ()

    int
    vips_smartcrop (VipsImage *in,
                    VipsImage **out,
                    int width,
                    int height,
                    ...);

Optional arguments:

- `interesting` : VipsInteresting to use to find interesting areas (default: VIPS_INTERESTING_ATTENTION)

Crop an image down to a specified width and height by removing boring parts.

Use `interesting` to pick the method vips uses to decide which bits of the image should be kept.

You can test xoffset / yoffset on `out` to find the location of the crop within the input image.

See also: `vips_extract_area()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
width | width of area to extract |
height | height of area to extract |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_extract_band ()

    int
    vips_extract_band (VipsImage *in,
                       VipsImage **out,
                       int band,
                       ...);

Optional arguments:

- `n` : number of bands to extract

Extract a band or bands from an image. Extracting out of range is an error.

See also: `vips_extract_area()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
band | band to extract |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_replicate ()

    int
    vips_replicate (VipsImage *in,
                    VipsImage **out,
                    int across,
                    int down,
                    ...);

Repeats an image many times.

See also: `vips_extract_area()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
across | repeat input this many times across |
down | repeat input this many times down |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_grid ()

    int
    vips_grid (VipsImage *in,
               VipsImage **out,
               int tile_height,
               int across,
               int down,
               ...);

Chop a tall thin image up into a set of tiles, lay the tiles out in a grid.

The input image should be a very tall, thin image containing a list of smaller images. Volumetric or time-sequence images are often laid out like this. This image is chopped into a series of tiles, each `tile_height` pixels high and the width of `in` . The tiles are then rearranged into a grid `across` tiles across and `down` tiles down in row-major order.

Supplying `tile_height` , `across` and `down` is not strictly necessary, we only really need two of these. Requiring three is a double-check that the image has the expected geometry.

See also: `vips_embed()`, `vips_insert()`, `vips_join()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
tile_height | chop into tiles this high |
across | tiles across |
down | tiles down |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_transpose3d ()

    int
    vips_transpose3d (VipsImage *in,
                      VipsImage **out,
                      ...);

Optional arguments:

`page_height` : `gint`, size of each input page

Transpose a volumetric image.

Volumetric images are very tall, thin images, with the metadata item VIPS_META_PAGE_HEIGHT set to the height of each sub-image.

This operation swaps the two major dimensions, so that page N in the output contains the Nth scanline, in order, from each input page.

You can override the VIPS_META_PAGE_HEIGHT metadata item with the optional `page_height` parameter.

VIPS_META_PAGE_HEIGHT in the output image is the number of pages in the input image.

See also: `vips_grid()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_wrap ()

    int
    vips_wrap (VipsImage *in,
               VipsImage **out,
               ...);

Optional arguments:

- `x` : horizontal displacement

- `y` : vertical displacement

Slice an image up and move the segments about so that the pixel that was at 0, 0 is now at `x` , `y` . If `x` and `y` are not set, they default to the centre of the image.

See also: `vips_embed()`, `vips_replicate()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_rot ()

    int
    vips_rot (VipsImage *in,
              VipsImage **out,
              VipsAngle angle,
              ...);

Rotate `in` by a multiple of 90 degrees.

Use `vips_similarity()` to rotate by an arbitary angle. `vips_rot45()` is useful for rotating convolution masks by 45 degrees.

See also: `vips_flip()`, `vips_similarity()`, `vips_rot45()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
angle | rotation angle |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_rot90 ()

    int
    vips_rot90 (VipsImage *in,
                VipsImage **out,
                ...);

Rotate `in` by 90 degress clockwise. A convenience function over `vips_rot()`.

See also: `vips_rot()`.

#### Parameters

in | input image |
out | output image |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_rot180 ()

    int
    vips_rot180 (VipsImage *in,
                 VipsImage **out,
                 ...);

Rotate `in` by 180 degress. A convenience function over `vips_rot()`.

See also: `vips_rot()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_rot270 ()

    int
    vips_rot270 (VipsImage *in,
                 VipsImage **out,
                 ...);

Rotate `in` by 270 degress clockwise. A convenience function over `vips_rot()`.

See also: `vips_rot()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_rot45 ()

    int
    vips_rot45 (VipsImage *in,
                VipsImage **out,
                ...);

Optional arguments:

- `angle` : VipsAngle45 rotation angle

Rotate `in` by a multiple of 45 degrees. Odd-length sides and square images only.

This operation is useful for rotating convolution masks. Use `vips_similarity()` to rotate images by arbitrary angles.

See also: `vips_rot()`, `vips_similarity()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_autorot_get_angle ()

    VipsAngle
    vips_autorot_get_angle (VipsImage *image);

Examine the metadata on `im` and return the VipsAngle to rotate by to turn the image upright.

See also: `vips_autorot()`.

#### Parameters

image | image to fetch orientation from |

#### Returns

the VipsAngle to rotate by to make the image upright.

### vips_autorot_remove_angle ()

    void
    vips_autorot_remove_angle (VipsImage *image);

Remove the orientation tag on `image` . Also remove any exif orientation tags.

See also: `vips_autorot_get_angle()`.

[method]

#### Parameters

image | image to remove orientation from |

### vips_autorot ()

    int
    vips_autorot (VipsImage *in,
                  VipsImage **out,
                  ...);

Optional arguments:

- `angle` : output VipsAngle the image was rotated by

Look at the image metadata and rotate the image to make it upright. The VIPS_META_ORIENTATION tag is removed from `out` to prevent accidental double rotation.

Read `angle` to find the amount the image was rotated by.

vips only supports the four simple rotations, it does not support the various mirror modes. If the image is using one of these mirror modes, the image is not rotated and the VIPS_META_ORIENTATION tag is not removed.

See also: `vips_autorot_get_angle()`, `vips_autorot_remove_angle()`, `vips_rot()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_zoom ()

    int
    vips_zoom (VipsImage *in,
               VipsImage **out,
               int xfac,
               int yfac,
               ...);

Zoom an image by repeating pixels. This is fast nearest-neighbour zoom.

See also: `vips_affine()`, `vips_subsample()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
xfac | horizontal scale factor |
yfac | vertical scale factor |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_subsample ()

    int
    vips_subsample (VipsImage *in,
                    VipsImage **out,
                    int xfac,
                    int yfac,
                    ...);

Optional arguments:

- `point` : turn on point sample mode

Subsample an image by an integer fraction. This is fast, nearest-neighbour shrink.

For small horizontal shrinks, this operation will fetch lines of pixels from `in` and then subsample that line. For large shrinks it will fetch single pixels.

If `point` is set, `in` will always be sampled in points. This can be faster if the previous operations in the pipeline are very slow.

See also: `vips_affine()`, `vips_shrink()`, `vips_zoom()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
xfac | horizontal shrink factor |
yfac | vertical shrink factor |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_cast ()

    int
    vips_cast (VipsImage *in,
               VipsImage **out,
               VipsBandFormat format,
               ...);

Optional arguments:

- `shift` : `gboolean`, integer values are shifted

Convert `in` to `format` . You can convert between any pair of formats. Floats are truncated (not rounded). Out of range values are clipped.

Casting from complex to real returns the real part.

If `shift` is `TRUE`, integer values are shifted up and down. For example, casting from unsigned 8 bit to unsigned 16 bit would shift every value left by 8 bits. The bottom bit is copied into the new bits, so 255 would become 65535.

See also: `vips_scale()`, `vips_complexform()`, `vips_real()`, `vips_imag()`, `vips_cast_uchar()`, `vips_msb()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
format | format to convert to |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_uchar ()

    int
    vips_cast_uchar (VipsImage *in,
                     VipsImage **out,
                     ...);

Convert `in` to VIPS_FORMAT_UCHAR. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_char ()

    int
    vips_cast_char (VipsImage *in,
                    VipsImage **out,
                    ...);

Convert `in` to VIPS_FORMAT_CHAR. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_ushort ()

    int
    vips_cast_ushort (VipsImage *in,
                      VipsImage **out,
                      ...);

Convert `in` to VIPS_FORMAT_USHORT. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_short ()

    int
    vips_cast_short (VipsImage *in,
                     VipsImage **out,
                     ...);

Convert `in` to VIPS_FORMAT_SHORT. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_uint ()

    int
    vips_cast_uint (VipsImage *in,
                    VipsImage **out,
                    ...);

Convert `in` to VIPS_FORMAT_UINT. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_int ()

    int
    vips_cast_int (VipsImage *in,
                   VipsImage **out,
                   ...);

Convert `in` to VIPS_FORMAT_INT. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_float ()

    int
    vips_cast_float (VipsImage *in,
                     VipsImage **out,
                     ...);

Convert `in` to VIPS_FORMAT_FLOAT. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_double ()

    int
    vips_cast_double (VipsImage *in,
                      VipsImage **out,
                      ...);

Convert `in` to VIPS_FORMAT_DOUBLE. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_complex ()

    int
    vips_cast_complex (VipsImage *in,
                       VipsImage **out,
                       ...);

Convert `in` to VIPS_FORMAT_COMPLEX. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_cast_dpcomplex ()

    int
    vips_cast_dpcomplex (VipsImage *in,
                         VipsImage **out,
                         ...);

Convert `in` to VIPS_FORMAT_DPCOMPLEX. See `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_scale ()

    int
    vips_scale (VipsImage *in,
                VipsImage **out,
                ...);

Optional arguments:

- `log` : log scale pixels

- `exp` : exponent for log scale

Search the image for the maximum and minimum value, then return the image as unsigned 8-bit, scaled so that the maximum value is 255 and the minimum is zero.

If `log` is set, transform with log10(1.0 + pow(x, `exp` )) + .5, then scale so max == 255. By default, `exp` is 0.25.

See also: `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_msb ()

    int
    vips_msb (VipsImage *in,
              VipsImage **out,
              ...);

Optional arguments:

- `band` : `gint`, msb just this band

Turn any integer image to 8-bit unsigned char by discarding all but the most significant byte. Signed values are converted to unsigned by adding 128.

Use `band` to make a one-band 8-bit image.

This operator also works for LABQ coding.

See also: `vips_scale()`, `vips_cast()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_byteswap ()

    int
    vips_byteswap (VipsImage *in,
                   VipsImage **out,
                   ...);

Swap the byte order in an image.

See also: `vips_rawload()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_bandjoin ()

    int
    vips_bandjoin (VipsImage **in,
                   VipsImage **out,
                   int n,
                   ...);

Join a set of images together, bandwise.

If the images have n and m bands, then the output image will have n + m bands, with the first n coming from the first image and the last m from the second.

If the images differ in size, the smaller images are enlarged to match the larger by adding zero pixels along the bottom and right.

The input images are cast up to the smallest common type (see table Smallest common format in

arithmetic).

See also: `vips_insert()`.

#### Parameters

in | array of input images. | [array length=n][transfer none]
out | output image. | [out]
n | number of input images |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandjoin2 ()

    int
    vips_bandjoin2 (VipsImage *in1,
                    VipsImage *in2,
                    VipsImage **out,
                    ...);

Join a pair of images together, bandwise. See `vips_bandjoin()`.

#### Parameters

in1 | first input image |
in2 | second input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandjoin_const ()

    int
    vips_bandjoin_const (VipsImage *in,
                         VipsImage **out,
                         double *c,
                         int n,
                         ...);

Append a set of constant bands to an image.

See also: `vips_bandjoin()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
c | array of constants to append. | [array length=n]
n | number of constants |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandjoin_const1 ()

    int
    vips_bandjoin_const1 (VipsImage *in,
                          VipsImage **out,
                          double c,
                          ...);

Append a single constant band to an image.

[method]

#### Parameters

in | input image |
out | output image. | [out]
c | constant to append |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandrank ()

    int
    vips_bandrank (VipsImage **in,
                   VipsImage **out,
                   int n,
                   ...);

Optional arguments:

- `index` : pick this index from list of sorted values

Sorts the images `in` band-element-wise, then outputs an image in which each band element is selected from the sorted list by the `index` parameter. For example, if `index` is zero, then each output band element will be the minimum of all the corresponding input band elements.

By default, `index` is -1, meaning pick the median value.

It works for any uncoded, non-complex image type. Images are cast up to the smallest common-format.

Any image can have either 1 band or n bands, where n is the same for all the non-1-band images. Single band images are then effectively copied to make n-band images.

Smaller input images are expanded by adding black pixels.

See also: `vips_rank()`.

#### Parameters

in | array of input images. | [array length=n]
out | output image. | [out]
n | number of input images |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandfold ()

    int
    vips_bandfold (VipsImage *in,
                   VipsImage **out,
                   ...);

Optional arguments:

- `factor` : fold by this factor

Fold up an image horizontally: width is collapsed into bands. Use `factor` to set how much to fold by: `factor` 3, for example, will make the output image three times narrower than the input, and with three times as many bands. By default the whole of the input width is folded up.

See also: `vips_csvload()`, `vips_bandunfold()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_bandunfold ()

    int
    vips_bandunfold (VipsImage *in,
                     VipsImage **out,
                     ...);

Optional arguments:

- `factor` : unfold by this factor

Unfold image bands into x axis. Use `factor` to set how much to unfold by: `factor` 3, for example, will make the output image three times wider than the input, and with one third as many bands. By default, all bands are unfolded.

See also: `vips_csvload()`, `vips_bandfold()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error.

### vips_bandbool ()

    int
    vips_bandbool (VipsImage *in,
                   VipsImage **out,
                   VipsOperationBoolean boolean,
                   ...);

Perform various boolean operations across the bands of an image. For example, a three-band uchar image operated on with VIPS_OPERATION_BOOLEAN_AND will produce a one-band uchar image where each pixel is the bitwise and of the band elements of the corresponding pixel in the input image.

The output image is the same format as the input image for integer types. Float types are cast to int before processing. Complex types are not supported.

The output image always has one band.

This operation is useful in conjuction with `vips_relational()`. You can use it to see if all image bands match exactly.

See also: `vips_boolean_const()`.

[method]

#### Parameters

in | left-hand input VipsImage |
out | output VipsImage. | [out]
boolean | boolean operation to perform |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandand ()

    int
    vips_bandand (VipsImage *in,
                  VipsImage **out,
                  ...);

Perform VIPS_OPERATION_BOOLEAN_AND on an image. See `vips_bandbool()`.

[method]

#### Parameters

in | left-hand input VipsImage |
out | output VipsImage. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandor ()

    int
    vips_bandor (VipsImage *in,
                 VipsImage **out,
                 ...);

Perform VIPS_OPERATION_BOOLEAN_OR on an image. See `vips_bandbool()`.

[method]

#### Parameters

in | left-hand input VipsImage |
out | output VipsImage. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandeor ()

    int
    vips_bandeor (VipsImage *in,
                  VipsImage **out,
                  ...);

Perform VIPS_OPERATION_BOOLEAN_EOR on an image. See `vips_bandbool()`.

[method]

#### Parameters

in | left-hand input VipsImage |
out | output VipsImage. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_bandmean ()

    int
    vips_bandmean (VipsImage *in,
                   VipsImage **out,
                   ...);

This operation writes a one-band image where each pixel is the average of the bands for that pixel in the input image. The output band format is the same as the input band format. Integer types use round-to-nearest averaging.

See also: `vips_add()`, `vips_avg()`, `vips_recomb()`

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_recomb ()

    int
    vips_recomb (VipsImage *in,
                 VipsImage **out,
                 VipsImage *m,
                 ...);

This operation recombines an image's bands. Each pixel in `in` is treated as an n-element vector, where n is the number of bands in `in` , and multipled by the n x m matrix `m` to produce the m-band image `out` .

`out` is always float, unless `in` is double, in which case `out` is double too. No complex images allowed.

It's useful for various sorts of colour space conversions.

See also: `vips_bandmean()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
m | recombination matrix |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_ifthenelse ()

    int
    vips_ifthenelse (VipsImage *cond,
                     VipsImage *in1,
                     VipsImage *in2,
                     VipsImage **out,
                     ...);

Optional arguments:

- `blend` : blend smoothly between `in1` and `in2`

This operation scans the condition image `cond` and uses it to select pixels from either the then image `in1` or the else image `in2` . Non-zero means `in1` , 0 means `in2` .

Any image can have either 1 band or n bands, where n is the same for all the non-1-band images. Single band images are then effectively copied to make n-band images.

Images `in1` and `in2` are cast up to the smallest common format. `cond` is cast to uchar.

If the images differ in size, the smaller images are enlarged to match the largest by adding zero pixels along the bottom and right.

If `blend` is `TRUE`, then values in `out` are smoothly blended between `in1` and `in2` using the formula:

`out` = (`cond` / 255) * `in1` + (1 - `cond` / 255) * `in2`

See also: `vips_equal()`.

#### Parameters

cond | condition VipsImage |
in1 | then VipsImage |
in2 | else VipsImage |
out | output VipsImage. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_switch ()

    int
    vips_switch (VipsImage **tests,
                 VipsImage **out,
                 int n,
                 ...);

The `tests` images are evaluated and at each point the index of the first non-zero value is written to `out` . If all `tests` are false, the value (`n` + 1) is written.

Images in `tests` must have one band. They are expanded to the bounding box of the set of images in `tests` , and that size is used for `out` . `tests` can have up to 255 elements.

Combine with `vips_case()` to make an efficient multi-way `vips_ifthenelse()`.

See also: `vips_maplut()`, `vips_case()`, `vips_ifthenelse()`.

[method]

#### Parameters

tests | test these images. | [array length=n]
out | output index image. | [out]
n | number of input images |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_flatten ()

    int
    vips_flatten (VipsImage *in,
                  VipsImage **out,
                  ...);

Optional arguments:

- `background` : VipsArrayDouble colour for new pixels

- `max_alpha` : `gdouble`, maximum value for alpha

Take the last band of `in` as an alpha and use it to blend the remaining channels with `background` .

The alpha channel is 0 - `max_alpha` , where 1 means 100% image and 0 means 100% background. Non-complex images only. `background` defaults to zero (black).

`max_alpha` has the default value 255, or 65535 for images tagged as VIPS_INTERPRETATION_RGB16 or VIPS_INTERPRETATION_GREY16.

Useful for flattening PNG images to RGB.

See also: `vips_premultiply()`, `vips_pngload()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_addalpha ()

    int
    vips_addalpha (VipsImage *in,
                   VipsImage **out,
                   ...);

Append an alpha channel.

See also: `vips_image_hasalpha()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_premultiply ()

    int
    vips_premultiply (VipsImage *in,
                      VipsImage **out,
                      ...);

Optional arguments:

- `max_alpha` : `gdouble`, maximum value for alpha

Premultiplies any alpha channel. The final band is taken to be the alpha and the bands are transformed as:

    1
    2
    3

    alpha = clip( 0, in[in.bands - 1], @max_alpha );
    norm = alpha / @max_alpha;
    out = [in[0] * norm, ..., in[in.bands - 1] * norm, alpha];

So for an N-band image, the first N - 1 bands are multiplied by the clipped and normalised final band, the final band is clipped. If there is only a single band, the image is passed through unaltered.

The result is VIPS_FORMAT_FLOAT unless the input format is VIPS_FORMAT_DOUBLE, in which case the output is double as well.

`max_alpha` has the default value 255, or 65535 for images tagged as VIPS_INTERPRETATION_RGB16 or VIPS_INTERPRETATION_GREY16.

Non-complex images only.

See also: `vips_unpremultiply()`, `vips_flatten()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_unpremultiply ()

    int
    vips_unpremultiply (VipsImage *in,
                        VipsImage **out,
                        ...);

Optional arguments:

- `max_alpha` : `gdouble`, maximum value for alpha

- `alpha_band` : `gint`, band containing alpha data

Unpremultiplies any alpha channel. Band `alpha_band` (by default the final band) contains the alpha and all other bands are transformed as:

    1
    2
    3
    4
    5
    6

    alpha = (int) clip( 0, in[in.bands - 1], @max_alpha );
    norm = (double) alpha / @max_alpha;
    if( alpha == 0 )
    	out = [0, ..., 0, alpha];
    else
    	out = [in[0] / norm, ..., in[in.bands - 1] / norm, alpha];

So for an N-band image, the first N - 1 bands are divided by the clipped and normalised final band, the final band is clipped. If there is only a single band, the image is passed through unaltered.

The result is VIPS_FORMAT_FLOAT unless the input format is VIPS_FORMAT_DOUBLE, in which case the output is double as well.

`max_alpha` has the default value 255, or 65535 for images tagged as VIPS_INTERPRETATION_RGB16 or VIPS_INTERPRETATION_GREY16.

Non-complex images only.

See also: `vips_premultiply()`, `vips_flatten()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_composite ()

    int
    vips_composite (VipsImage **in,
                    VipsImage **out,
                    int n,
                    int *mode,
                    ...);

Optional arguments:

- `compositing_space` : VipsInterpretation to composite in

- `premultiplied` : `gboolean`, images are already premultiplied

- `x` : VipsArrayInt, position of subimages

- `y` : VipsArrayInt, position of subimages

Composite an array of images together.

Images are placed in a stack, with `in` [0] at the bottom and `in` [`n` - 1] at the top. Pixels are blended together working from the bottom upwards, with the blend mode at each step being set by the corresponding VipsBlendMode in `mode` .

Images are transformed to a compositing space before processing. This is VIPS_INTERPRETATION_sRGB, VIPS_INTERPRETATION_B_W, VIPS_INTERPRETATION_RGB16, or VIPS_INTERPRETATION_GREY16 by default, depending on how many bands and bits the input images have. You can select any other space, such as VIPS_INTERPRETATION_LAB or VIPS_INTERPRETATION_scRGB.

The output image is in the compositing space. It will always be VIPS_FORMAT_FLOAT unless one of the inputs is VIPS_FORMAT_DOUBLE, in which case the output will be double as well.

Complex images are not supported.

The output image will always have an alpha band. A solid alpha is added to any input missing an alpha.

The images do not need to match in size or format. They will be expanded to the smallest common size and format in the usual way. Images are positioned using the `x` and `y` parameters, if set.

Image are normally treated as unpremultiplied, so this operation can be used directly on PNG images. If your images have been through `vips_premultiply()`, set `premultiplied` .

See also: `vips_insert()`.

[method]

#### Parameters

in | array of input images. | [array length=n][transfer none]
out | output image. | [out]
n | number of input images |
mode | array of (`n` - 1) VipsBlendMode |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_composite2 ()

    int
    vips_composite2 (VipsImage *base,
                     VipsImage *overlay,
                     VipsImage **out,
                     VipsBlendMode mode1,
                     ...);

Optional arguments:

- `compositing_space` : VipsInterpretation to composite in

- `premultiplied` : `gboolean`, images are already premultiplied

- `x` : `gint`, position of overlay

- `y` : `gint`, position of overlay

Composite `overlay` on top of `base` with `mode` . See `vips_composite()`.

[method]

#### Parameters

base | first input image |
overlay | second input image |
out | output image. | [out]
mode | composite with this blend mode |
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_falsecolour ()

    int
    vips_falsecolour (VipsImage *in,
                      VipsImage **out,
                      ...);

Force `in` to 1 band, 8-bit, then transform to a 3-band 8-bit image with a false colour map. The map is supposed to make small differences in brightness more obvious.

See also: `vips_maplut()`.

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

### vips_gamma ()

    int
    vips_gamma (VipsImage *in,
                VipsImage **out,
                ...);

Optional arguments:

- `exponent` : gamma, default 1.0 / 2.4

Calculate `in` ** (1 / `exponent` ), normalising to the maximum range of the input type. For float types use 1.0 as the maximum.

See also: `vips_identity()`, `vips_pow_const1()`, `vips_maplut()`

[method]

#### Parameters

in | input image |
out | output image. | [out]
... | `NULL`-terminated list of optional named arguments |

#### Returns

0 on success, -1 on error

## Types and Values

### enum VipsExtend

See `vips_embed()`, `vips_conv()`, `vips_affine()` and so on.

When the edges of an image are extended, you can specify how you want the extension done.

VIPS_EXTEND_BLACK --- new pixels are black, ie. all bits are zero.

VIPS_EXTEND_COPY --- each new pixel takes the value of the nearest edge pixel

VIPS_EXTEND_REPEAT --- the image is tiled to fill the new area

VIPS_EXTEND_MIRROR --- the image is reflected and tiled to reduce hash edges

VIPS_EXTEND_WHITE --- new pixels are white, ie. all bits are set

VIPS_EXTEND_BACKGROUND --- colour set from the `background` property

We have to specify the exact value of each enum member since we have to keep these frozen for back compat with vips7.

See also: `vips_embed()`.

#### Members

VIPS_EXTEND_BLACK | extend with black (all 0) pixels |
VIPS_EXTEND_COPY | copy the image edges |
VIPS_EXTEND_REPEAT | repeat the whole image |
VIPS_EXTEND_MIRROR | mirror the whole image |
VIPS_EXTEND_WHITE | extend with white (all bits set) pixels |
VIPS_EXTEND_BACKGROUND | extend with colour from the `background` property |
VIPS_EXTEND_LAST |  |

### enum VipsCompassDirection

A direction on a compass. Used for `vips_gravity()`, for example.

#### Members

VIPS_COMPASS_DIRECTION_CENTRE | centre |
VIPS_COMPASS_DIRECTION_NORTH | north |
VIPS_COMPASS_DIRECTION_EAST | east |
VIPS_COMPASS_DIRECTION_SOUTH | south |
VIPS_COMPASS_DIRECTION_WEST | west |
VIPS_COMPASS_DIRECTION_NORTH_EAST | north-east |
VIPS_COMPASS_DIRECTION_SOUTH_EAST | south-east |
VIPS_COMPASS_DIRECTION_SOUTH_WEST | south-west |
VIPS_COMPASS_DIRECTION_NORTH_WEST | north-west |
VIPS_COMPASS_DIRECTION_LAST |  |

### enum VipsDirection

See `vips_flip()`, `vips_join()` and so on.

Operations like `vips_flip()` need to be told whether to flip left-right or top-bottom.

See also: `vips_flip()`, `vips_join()`.

#### Members

VIPS_DIRECTION_HORIZONTAL | left-right |
VIPS_DIRECTION_VERTICAL | top-bottom |
VIPS_DIRECTION_LAST |  |

### enum VipsAlign

See `vips_join()` and so on.

Operations like `vips_join()` need to be told whether to align images on the low or high coordinate edge, or centre.

See also: `vips_join()`.

#### Members

VIPS_ALIGN_LOW | align low coordinate edge |
VIPS_ALIGN_CENTRE | align centre |
VIPS_ALIGN_HIGH | align high coordinate edge |
VIPS_ALIGN_LAST |  |

### enum VipsAngle

See `vips_rot()` and so on.

Fixed rotate angles.

See also: `vips_rot()`.

#### Members

VIPS_ANGLE_D0 | no rotate |
VIPS_ANGLE_D90 | 90 degrees clockwise |
VIPS_ANGLE_D180 | 180 degree rotate |
VIPS_ANGLE_D270 | 90 degrees anti-clockwise |
VIPS_ANGLE_LAST |  |

### enum VipsAngle45

See `vips_rot45()` and so on.

Fixed rotate angles.

See also: `vips_rot45()`.

#### Members

VIPS_ANGLE45_D0 | no rotate |
VIPS_ANGLE45_D45 | 45 degrees clockwise |
VIPS_ANGLE45_D90 | 90 degrees clockwise |
VIPS_ANGLE45_D135 | 135 degrees clockwise |
VIPS_ANGLE45_D180 | 180 degrees |
VIPS_ANGLE45_D225 | 135 degrees anti-clockwise |
VIPS_ANGLE45_D270 | 90 degrees anti-clockwise |
VIPS_ANGLE45_D315 | 45 degrees anti-clockwise |
VIPS_ANGLE45_LAST |  |

### enum VipsInteresting

Pick the algorithm vips uses to decide image "interestingness". This is used by `vips_smartcrop()`, for example, to decide what parts of the image to keep.

VIPS_INTERESTING_NONE and VIPS_INTERESTING_LOW mean the same -- the crop is positioned at the top or left. VIPS_INTERESTING_HIGH positions at the bottom or right.

See also: `vips_smartcrop()`.

#### Members

VIPS_INTERESTING_NONE | do nothing |
VIPS_INTERESTING_CENTRE | just take the centre |
VIPS_INTERESTING_ENTROPY | use an entropy measure |
VIPS_INTERESTING_ATTENTION | look for features likely to draw human attention |
VIPS_INTERESTING_LOW | position the crop towards the low coordinate |
VIPS_INTERESTING_HIGH | position the crop towards the high coordinate |
VIPS_INTERESTING_LAST |  |

### enum VipsBlendMode

The various Porter-Duff and PDF blend modes. See `vips_composite()`, for example.

The Cairo docs have a nice explanation of all the blend modes:

https://www.cairographics.org/operators

The non-separable modes are not implemented.

#### Members

VIPS_BLEND_MODE_CLEAR | where the second object is drawn, the first is removed |
VIPS_BLEND_MODE_SOURCE | the second object is drawn as if nothing were below |
VIPS_BLEND_MODE_OVER | the image shows what you would expect if you held two semi-transparent slides on top of each other |
VIPS_BLEND_MODE_IN | the first object is removed completely, the second is only drawn where the first was |
VIPS_BLEND_MODE_OUT | the second is drawn only where the first isn't |
VIPS_BLEND_MODE_ATOP | this leaves the first object mostly intact, but mixes both objects in the overlapping area |
VIPS_BLEND_MODE_DEST | leaves the first object untouched, the second is discarded completely |
VIPS_BLEND_MODE_DEST_OVER | like OVER, but swaps the arguments |
VIPS_BLEND_MODE_DEST_IN | like IN, but swaps the arguments |
VIPS_BLEND_MODE_DEST_OUT | like OUT, but swaps the arguments |
VIPS_BLEND_MODE_DEST_ATOP | like ATOP, but swaps the arguments |
VIPS_BLEND_MODE_XOR | something like a difference operator |
VIPS_BLEND_MODE_ADD | a bit like adding the two images |
VIPS_BLEND_MODE_SATURATE | a bit like the darker of the two |
VIPS_BLEND_MODE_MULTIPLY | at least as dark as the darker of the two inputs |
VIPS_BLEND_MODE_SCREEN | at least as light as the lighter of the inputs |
VIPS_BLEND_MODE_OVERLAY | multiplies or screens colors, depending on the lightness |
VIPS_BLEND_MODE_DARKEN | the darker of each component |
VIPS_BLEND_MODE_LIGHTEN | the lighter of each component |
VIPS_BLEND_MODE_COLOUR_DODGE | brighten first by a factor second |
VIPS_BLEND_MODE_COLOUR_BURN | darken first by a factor of second |
VIPS_BLEND_MODE_HARD_LIGHT | multiply or screen, depending on lightness |
VIPS_BLEND_MODE_SOFT_LIGHT | darken or lighten, depending on lightness |
VIPS_BLEND_MODE_DIFFERENCE | difference of the two |
VIPS_BLEND_MODE_EXCLUSION | somewhat like DIFFERENCE, but lower-contrast |
VIPS_BLEND_MODE_LAST |  |

## See Also

resample