Provided by: libafterimage-dev_2.2.12-15_amd64 bug

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

           #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> ...]\n");
               printf( "  Where: geometry - size of the resulting image and window;\n");
               printf( "         gradient_type - One of the fiollowing values :\n");
               printf( "            0 - linear   left-to-right gradient,\n");
               printf( "            1 - diagonal lefttop-to-rightbottom,\n");
               printf( "            2 - linear   top-to-bottom gradient,\n");
               printf( "            3 - diagonal righttop-to-leftbottom;\n");
               printf( "         offset   - floating point value from 0.0 to 1.0\n"); }

           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%d\n",
                       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 ; }

       libAfterImage/tutorials/ASGrad.1 [5.1]

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
       libAfterImage/tutorials/ASGrad.2 [5.2]

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 one 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.