AFTERImage example 5: Gradient rendering

libAfterImage/tutorials/ASGrad

• NAME

  ASGrad

• 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.
  

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