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# AFTERImage example 4: Image blending

demonstrates blending of multiple image using different algorithms

libAfterImage/tutorials/ASMerge

- NAME

  ASMerge

- SYNOPSIS

      Scaling and blending of arbitrary number of images
      using libAfterImage.

- DESCRIPTION

      We will attempt to interpret command line arguments as sequence of
      image filenames, geometries and blending types. We'll then try and
      load all the images, scaling first one to requested size, and
      blending others at specifyed locations of the first image.
      We then display the result in simple window.
      After that we would want to wait, until user closes our window.

      New steps described in this tutorial are :
      Step 1. Layers.
      Step 2. Merging methods.
      Step 3. Layer parameters.
      Step 4. Actual blending of the set of images.

- 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

- SOURCE

      #include "../afterbase.h"
      #include "../afterimage.h"
      #include "common.h"

      char *burning_rose[] =
      {
          "asmerge",
          "rose512.jpg",
          "add",
          "back.xpm:512x386",
          "hue",
          "fore.xpm:512x386"
      };

      void usage()
      {
          printf( "Usage: asmerge [-h]|[image op1 image1 [op2 image2 [...]]]\n");
          printf( "Where: image  - is background image filename\n");
          printf( "       image1 - is first overlay's filename\n");
          printf( "       op1,op2,... - overlay operation."
                  " Supported operations are :\n");
          list_scanline_merging( stdout,
                  "         %-15.15s- %s\n");
      }

      int main(int argc, char* argv[])
      {
          Display *dpy = NULL;
          ASVisual *asv ;
          int screen = 0, depth = 0;
          int to_width = 1, to_height = 1;
          ASImageLayer *layers ;
          int layers_num = 0, i;
          ASImage *merged_im ;

          /* see ASView.1 : */
          set_application_name( argv[0] );
      #if (HAVE_AFTERBASE_FLAG==1)
          set_output_threshold(OUTPUT_LEVEL_DEBUG);
      #endif
          if( argc == 2 && strncmp(argv[1],"-h", 2) == 0 )
          {
              usage();
              return 0;
          }
          if( argc <= 3 )
          {
              show_error( "not enough arguments, please see usage:%s", " ");
              usage() ;
              printf( "Using the default, \"The Burning Rose\", composition :\n");
              printf( "\n\trose512.jpg add back.xpm:512x386 hue "
                      "fore.xpm:512x386\n");
              argv = &(burning_rose[0]) ;
              argc = 6;
          }

      #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
          /* see ASView.3 : */
          asv = create_asvisual( dpy, screen, depth, NULL );

          /* see ASMerge.1 : */
          layers = safecalloc( argc/2, sizeof(ASImageLayer) );

          for( i = 1 ; i < argc ; i++ )
          {
              int x = 0, y = 0;
              unsigned int width, height ;
              int geom_flags = 0 ;
              char *separator;
              char *filename ;
              /* see ASMerge.2 */
              if( i > 1 )
              {
                  /* see blend_scanlines_name2func() : */
                  if((layers[layers_num].merge_scanlines =
                       blend_scanlines_name2func( argv[i] )) == NULL )
                      continue ;
                  if( ++i >= argc )
                      break;
              }
              if( (separator = strchr( argv[i], ':' )) != NULL )
              {   /* see ASTile.1 : */
                  geom_flags = XParseGeometry( separator+1,
                                               &x, &y, &width, &height);
                  filename = mystrndup( argv[i], separator-argv[i] );
              }else
                  filename = argv[i] ;
              layers[layers_num].im = file2ASImage( filename, 0xFFFFFFFF,
                                                    SCREEN_GAMMA, 100, getenv("IMAGE_PATH"), NULL );
              if( filename != argv[i] )
                  free( filename );
              if( layers[layers_num].im != NULL )
              {
                  if( !get_flags(geom_flags, WidthValue) )
                      width = layers[layers_num].im->width  ;
                  if( !get_flags(geom_flags, HeightValue) )
                      height = layers[layers_num].im->height ;
                  /* see ASMerge.3 : */
                  if( layers[layers_num].merge_scanlines == NULL )
                      layers[layers_num].merge_scanlines =
                          alphablend_scanlines ;
                  layers[layers_num].clip_width = width ;
                  layers[layers_num].clip_height = height ;
                  if( layers_num > 0 )
                  {
                      layers[layers_num].dst_x = x ;
                      layers[layers_num].dst_y = y ;
                  }else
                  {
                      to_width = width ;
                      to_height = height ;
                      if( width != layers[layers_num].im->width ||
                          height != layers[layers_num].im->height )
                      {
                          ASImage *scaled_bottom ;
                          /* see ASScale.2 : */
                          scaled_bottom = scale_asimage( asv,
                                                         layers[layers_num].im,
                                                         width, height,
                                                         False, 100,
                                                      ASIMAGE_QUALITY_DEFAULT );
                          destroy_asimage( &(layers[layers_num].im) );
                          layers[layers_num].im = scaled_bottom ;
                      }
                  }
                  ++layers_num ;
              }
          }

          if( layers_num <= 0 )
          {
              show_error( "there is no images to merge. Aborting");
              return 2;
          }

          /* see ASMerge.4 */
          merged_im = merge_layers( asv, layers, layers_num,
                                    to_width, to_height,
      #ifndef X_DISPLAY_MISSING
                                    ASA_XImage,
      #else
                                    ASA_ASImage,
      #endif
                                    0, ASIMAGE_QUALITY_DEFAULT );
          while( --layers_num >= 0 )
              destroy_asimage( &(layers[layers_num].im) );
          free( layers );

          if( merged_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,
                                                  "ASMerge", NULL );
              if( w != None )
              {
                  Pixmap p ;

                  XMapRaised   (dpy, w);
                  /* see ASView.5 : */
                  p = asimage2pixmap( asv, DefaultRootWindow(dpy), merged_im,
                                  NULL, True );

                  destroy_asimage( &merged_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
              /* writing result into the file */
              ASImage2file( merged_im, NULL, "asmerge.jpg", ASIT_Jpeg, NULL );
              destroy_asimage( &merged_im );
      #endif
          }
      #ifdef DEBUG_ALLOCS
          build_xpm_colormap(NULL);
          print_unfreed_mem();
      #endif
          return 0 ;
      }

libAfterImage/tutorials/ASMerge.1 [4.1]

- SYNOPSIS

      Step 1. Layers.

- DESCRIPTION

      libAfterImage performs blending/merging of different images, using
      arrays of ASImageLayer structures, with first element representing
      the bottommost image. Each structure specifies exact position on
      resulting image where overlay should be blended to, tint of the
      overlay, size, to which overlay should be tiled, overlay's origin,
      and overlay's background color. Arbitrary number of layers can be
      merged whithin single run.

      Accordingly all that is needed to merge bunch of images is to create
      array of ASImageLayer structures and fill it up appropriately.

- EXAMPLE

          layers = safecalloc( argc/2, sizeof(ASImageLayer) );

libAfterImage/tutorials/ASMerge.2 [4.2]

- SYNOPSIS

      Step 2. Merging methods.

- DESCRIPTION

      Each layer can be merged in using its own method. There are about 15
      different methods implemented in libAfterImage, and user app can
      implement other methods of its own. To specify method all that is
      needed is to set merge_scanlines member of ASImageLayer to pointer
      to the function, implementing specific method.

      libAfterImage provides facility to parse method name strings into
      actuall function pointers. That could be used to simplifi scripting,
      etc.

- EXAMPLE

             if((layers[layers_num].merge_scanlines =
                 blend_scanlines_name2func( argv[i] )) == NULL )
                 continue ;
      NOTE
      All layers MUST have valid merge_scanlines pointer, even the
      bottommost layer, despite the fact that it has nothing to be merged
      with. If merge_scanlines is set to NULL - this layer will be ignored.
      That could be used to turn on/off particular layers.

libAfterImage/tutorials/ASMerge.3 [4.3]

- SYNOPSIS

      Step 3. Layer parameters.

- DESCRIPTION

      Several ASImageLayer members are mandatory and cannot be set to 0.
      Such as : im - image to be merged; clip_width, clip_height - this will
      be used to tile the image; merge_scanlines - must be set to a pointer
      to the function implementing merging method. If any of this is set
      to 0  - then layer will be ignored. The rest of the parameters are
      optional. Note thou that tint parameter will tint overlay's RGB
      components and alpha component, as the result it could be used to
      make opaque images - semitransparent.

- EXAMPLE

          if( layers[layers_num].merge_scanlines == NULL )
              layers[layers_num].merge_scanlines =
                  alphablend_scanlines ;
          layers[layers_num].clip_width = width ;
          layers[layers_num].clip_height = height ;
          if( layers_num > 0 )
          {
              layers[layers_num].dst_x = x ;
              layers[layers_num].dst_y = y ;
          }

libAfterImage/tutorials/ASMerge.4 [4.4]

- SYNOPSIS

      Step 4. Actual blending of the set of images.

- DESCRIPTION

      After set of layers has been prepared - it can be passed to
      merge_layers() function, that will create new ASImage of specifyed
      size, and then blend all the layers together to fill this image.

- EXAMPLE

              merged_im = merge_layers( asv, layers, layers_num,
                                        to_width, to_height,
                                        ASA_ASImage, 0,
                                        ASIMAGE_QUALITY_DEFAULT );
              while( --layers_num >= 0 )
                  destroy_asimage( &(layers[layers_num].im) );
              free( layers );

- NOTES

      After we've blended layers - we no longer need ASImageLayer array.
      So proceeding to clean it up, by destroying overlay AsImages first,
      and then freeing array itself.

- SEE ALSO

      merge_asimage().

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