asgrad(1)                AfterStep X11 window manager                asgrad(1)



NAME
       asgrad - demonstrates rendering of multi point linear gradients
       libAfterImage/tutorials/ASGrad

NAMEASGrad
SYNOPSIS
       libAfterImage application for drawing multipoint linear gradients.

DESCRIPTION
       New steps described in this tutorial are :
       ASGrad.1. Building gradient specs.
       ASGrad.2. Actual rendering gradient.

SEE ALSO
       Tutorial 1: ASView  - explanation of basic steps needed to use
                             libAfterImage and some other simple things.
       Tutorial 2: ASScale - image scaling basics.
       Tutorial 3: ASTile  - image tiling and tinting.
       Tutorial 4: ASMerge - scaling and blending of arbitrary number of
                             images.

SOURCE
       Source :
       #include "../afterbase.h"
       #include "../afterimage.h"
       #include "common.h"

       ARGB32 default_colors[] = {
           0xFF000000,
           0xFF700070,                                /* violet */
           0xFF0000FF,                                /* blue   */
           0xFF00FFFF,                                /* cyan   */
           0xFF00FF00,
           0XFFFFFF00,
           0XFF700000,
           0XFFFF0000,
           0xFF8080A0,
           0xFFE0E0FF,
           0xFFa0a0FF,
       };
       double default_offsets[] = { 0, 0.1, 0.15, 0.20, 0.35, 0.45, 0.55, 0.50,
                                    0.65, 0.8, 1.0} ;


       void usage()
       {
           printf( "  Usage: asgrad -h | <geometry> <gradient_type> <color1> "
                   "<offset2> <color2> [ <offset3> <color3> ...]0);
           printf( "  Where: geometry - size of the resulting image and window;0);
           printf( "         gradient_type - One of the fiollowing values :0);
           printf( "            0 - linear   left-to-right gradient,0);
           printf( "            1 - diagonal lefttop-to-rightbottom,0);
           printf( "            2 - linear   top-to-bottom gradient,0);
           printf( "            3 - diagonal righttop-to-leftbottom;0);
           printf( "         offset   - floating point value from 0.0 to 1.00);
       }

       int main(int argc, char* argv[])
       {
           Display *dpy = NULL;
           ASVisual *asv ;
           int screen = 0, depth = 0;
           int dummy, geom_flags = 0;
           unsigned int to_width, to_height ;
           ASGradient grad ;
           ASGradient default_grad = { 1, 11, &(default_colors[0]),
                                              &(default_offsets[0])} ;
           ASImage *grad_im = NULL;

           /* see ASView.1 : */
           set_application_name( argv[0] );
       #if (HAVE_AFTERBASE_FLAG==1)
           set_output_threshold(OUTPUT_LEVEL_DEBUG);
       #endif

           if( argc > 1 )
           {
               if( strcmp( argv[1], "-h") == 0 )
               {
                   usage();
                   return 0;
               }
               /* see ASScale.1 : */
               geom_flags = XParseGeometry( argv[1], &dummy, &dummy,
                                            &to_width, &to_height );
           }else
               usage();
           memset( &grad, 0x00, sizeof(ASGradient));

       #ifndef X_DISPLAY_MISSING
           dpy = XOpenDisplay(NULL);
           _XA_WM_DELETE_WINDOW = XInternAtom( dpy, "WM_DELETE_WINDOW", False);
           screen = DefaultScreen(dpy);
           depth = DefaultDepth( dpy, screen );
       #endif

           if( argc >= 5 )
           {
               int i = 2;
               /* see ASGrad.1 : */
               grad.type = atoi( argv[2] );
               grad.npoints = 0 ;
               grad.color = safemalloc( ((argc-2)/2)*sizeof(ARGB32));
               grad.offset = safemalloc( ((argc-2)/2)*sizeof(double));
               while( ++i < argc )
               {
                   if( grad.npoints > 0 )
                   {
                       if( i == argc-1 )
                           grad.offset[grad.npoints] = 1.0;
                       else
                           grad.offset[grad.npoints] = atof( argv[i] );
                       ++i ;
                   }

                   /* see ASTile.1 : */
                   if( parse_argb_color( argv[i], &(grad.color[grad.npoints]))
                       != argv[i] )
                       if( grad.offset[grad.npoints] >= 0. &&
                           grad.offset[grad.npoints]<= 1.0 )
                           grad.npoints++ ;
               }
           }else
           {
               grad = default_grad ;
               if( argc >= 3 )
                   grad.type = atoi( argv[2] );
           }

           if( grad.npoints <= 0 )
           {
               show_error( " not enough gradient points specified.");
               return 1;
           }

           /* Making sure tiling geometry is sane : */
       #ifndef X_DISPLAY_MISSING
           if( !get_flags(geom_flags, WidthValue ) )
               to_width  = DisplayWidth(dpy, screen)*2/3 ;
           if( !get_flags(geom_flags, HeightValue ) )
               to_height = DisplayHeight(dpy, screen)*2/3 ;
       #else
           if( !get_flags(geom_flags, WidthValue ) )
               to_width  = 500 ;
           if( !get_flags(geom_flags, HeightValue ) )
               to_height = 500 ;
       #endif
           printf( "%s: rendering gradient of type %d to %dx%d0,
                   get_application_name(), grad.type&GRADIENT_TYPE_MASK,
                   to_width, to_height );

           /* see ASView.3 : */
           asv = create_asvisual( dpy, screen, depth, NULL );
           /* see ASGrad.2 : */
           grad_im = make_gradient( asv, &grad, to_width, to_height,
                                    SCL_DO_ALL,
       #ifndef X_DISPLAY_MISSING
                                    ASA_XImage,
       #else
                                    ASA_ASImage,
       #endif
                                    0, ASIMAGE_QUALITY_DEFAULT );
           if( grad_im )
           {
       #ifndef X_DISPLAY_MISSING
               /* see ASView.4 : */
               Window w = create_top_level_window( asv,
                                                   DefaultRootWindow(dpy), 32, 32,
                                                   to_width, to_height, 1, 0, NULL,
                                                   "ASGradient", NULL );
               if( w != None )
               {
                   Pixmap p ;

                   XMapRaised   (dpy, w);
                   /* see ASView.5 : */
                   p = asimage2pixmap( asv, DefaultRootWindow(dpy), grad_im,
                                       NULL, True );
                   destroy_asimage( &grad_im );
                   /* see common.c: set_window_background_and_free() : */
                   p = set_window_background_and_free( w, p );
                   /* see common.c: wait_closedown() : */
               }
               wait_closedown(w);
               dpy = NULL;
       #else
               ASImage2file( grad_im, NULL, "asgrad.jpg", ASIT_Jpeg, NULL );
               destroy_asimage( &grad_im );
       #endif
           }
           return 0 ;
       }

SYNOPSIS
       Step 1. Building gradient specs.

DESCRIPTION
       Multipoint gradient is defined as set of color values with offsets
       of each point from the beginning of the gradient on 1.0 scale.
       Offsets of the first and last point in gradient should always be
       0. and 1.0 respectively, and other points should go in between.
       For example 2 point gradient will have always offsets 0. and 1.0,
       3 points gradient will have 0. for first color, 1.0 for last color
       and anything in between for middle color.
       If offset is incorrect - point will be skipped at the time of
       rendering.

       There are 4 types of gradients supported : horizontal, top-left to
       bottom-right diagonal, vertical and top-right to bottom-left diagonal.
       Any cilindrical gradient could be drawn as a 3 point gradient with
       border colors being the same.

       Each gradient point has ARGB color, which means that it is possible
       to draw gradients in alpha channel as well as RGB. That makes for
       semitransparent gradients, fading gradients, etc.

EXAMPLE
           grad.type = atoi( argv[2] );
               grad.npoints = 0 ;
               grad.color = safemalloc( ((argc-2)/2)*sizeof(ARGB32));
               grad.offset = safemalloc( ((argc-2)/2)*sizeof(double));
               while( ++i < argc )
               {
                   if( grad.npoints > 0 )
                   {
                       if( i == argc-1 )
                           grad.offset[grad.npoints] = 1.0;
                       else
                           grad.offset[grad.npoints] = atof( argv[i] );
                       ++i ;
                   }
               if( parse_argb_color( argv[i], &(grad.color[grad.npoints]))
                    != argv[i] )
                       if(grad.offset[grad.npoints] >= 0. &&
                       grad.offset[grad.npoints]<= 1.0 )
                           grad.npoints++ ;
               }

SEE ALSO
       ARGB32, parse_argb_color(), ASGradient

SYNOPSIS
       Step 2. Actually rendering gradient.

DESCRIPTION
       All that is needed to draw gradient is to call make_gradient(),
       passing pointer to ASGradient structure, that describes gradient.
       Naturally size of the gradient is needed too. Another parameter is
       filter - that is a bit mask that allows to draw gradient using only a
       subset of the channels, represented by set bits. SCL_DO_ALL means
       that all 4 channels must be rendered.
       make_gradient() creates ASImage of requested size and fills it with
       gradient. Special techinque based on error diffusion is utilized to
       avoid sharp steps between grades of colors when limited range of
       colors is used for gradient.

EXAMPLE
               grad_im = make_gradient( asv, &grad, to_width, to_height,
                                        SCL_DO_ALL,
                                    ASA_XImage, 0, ASIMAGE_QUALITY_DEFAULT );

NOTES
       make_gradient(), ASScanline, ASImage.



3rd Berkeley Distribution      AfterStep v.2.2.9                     asgrad(1)
