root/ext/gd/libgd/testac.c

DEFINITIONS

1. main
2. testDrawing

   1 
   2 #include <stdio.h>
   3 #include "gd.h"
   4 
   5 /* If palette is true, we convert from truecolor to palette at the end,
   6    to test gdImageTrueColorToPalette and see file size/
   7    quality tradeoffs. */
   8 
   9 void testDrawing (
  10                    gdImagePtr im_in,
  11                    double scale,
  12                    int blending,
  13                    int palette,
  14                    char *filename);
  15 
  16 int
  17 main (int argc, char *argv[])
  18 {
  19   /* Input and output files */
  20   FILE *in;
  21   FILE *out;
  22 
  23   /* Input image */
  24   gdImagePtr im_in = 0;
  25 
  26   /* Colors */
  27   int lightBlue;
  28 
  29   if (argc != 2)
  30     {
  31       fprintf (stderr, "Usage: testac filename.png\n");
  32       exit (1);
  33     }
  34   /* Load original PNG, which should contain alpha channel
  35      information. We will use it in two ways: preserving it
  36      literally, for use with compatible browsers, and
  37      compositing it ourselves against a background of our
  38      choosing (alpha blending). We'll change its size
  39      and try creating palette versions of it. */
  40   in = fopen (argv[1], "rb");
  41   if (!in)
  42     {
  43       fprintf (stderr, "Can't load %s.\n", argv[1]);
  44       exit (1);
  45     }
  46   else
  47     {
  48       im_in = gdImageCreateFromPng (in);
  49       fclose (in);
  50     }
  51   testDrawing (im_in, 1.0, 0, 0, "noblending-fullsize-truecolor.png");
  52   testDrawing (im_in, 1.0, 1, 0, "blending-fullsize-truecolor.png");
  53   testDrawing (im_in, 0.5, 0, 0, "noblending-halfsize-truecolor.png");
  54   testDrawing (im_in, 0.5, 1, 0, "blending-halfsize-truecolor.png");
  55   testDrawing (im_in, 2.0, 0, 0, "noblending-doublesize-truecolor.png");
  56   testDrawing (im_in, 2.0, 1, 0, "blending-doublesize-truecolor.png");
  57   testDrawing (im_in, 1.0, 0, 1, "noblending-fullsize-palette.png");
  58   testDrawing (im_in, 1.0, 1, 1, "blending-fullsize-palette.png");
  59   testDrawing (im_in, 0.5, 0, 1, "noblending-halfsize-palette.png");
  60   testDrawing (im_in, 0.5, 1, 1, "blending-halfsize-palette.png");
  61   testDrawing (im_in, 2.0, 0, 1, "noblending-doublesize-palette.png");
  62   testDrawing (im_in, 2.0, 1, 1, "blending-doublesize-palette.png");
  63   gdImageDestroy (im_in);
  64   return 0;
  65 }
  66 
  67 /* If palette is true, we convert from truecolor to palette at the end,
  68    to test gdImageTrueColorToPalette and see file size/
  69    quality tradeoffs. */
  70 void
  71 testDrawing (
  72               gdImagePtr im_in,
  73               double scale,
  74               int blending,
  75               int palette,
  76               char *filename)
  77 {
  78   gdImagePtr im_out;
  79   FILE *out;
  80   /* Create output image. */
  81   im_out = gdImageCreateTrueColor ((int) (gdImageSX (im_in) * scale),
  82                                    (int) (gdImageSY (im_in) * scale));
  83   /*
  84      Request alpha blending. This causes future
  85      drawing operations to perform alpha channel blending
  86      with the background, resulting in an opaque image.
  87      Without this call, pixels in the foreground color are
  88      copied literally, *including* the alpha channel value,
  89      resulting in an output image which is potentially
  90      not opaque. This flag can be set and cleared as often
  91      as desired. */
  92   gdImageAlphaBlending (im_out, blending);
  93 
  94   /* Flood with light blue. */
  95   gdImageFill (im_out, (int) (gdImageSX (im_in) * scale / 2),
  96                (int) (gdImageSY (im_in) * scale / 2),
  97                gdTrueColor (192, 192, 255));
  98   /* Copy the source image. Alpha blending should result in
  99      compositing against red. With blending turned off, the
 100      browser or viewer will composite against its preferred
 101      background, or, if it does not support an alpha channel,
 102      we will see the original colors for the pixels that
 103      ought to be transparent or semitransparent. */
 104   gdImageCopyResampled (im_out, im_in,
 105                         0, 0,
 106                         0, 0,
 107        (int) (gdImageSX (im_in) * scale), (int) (gdImageSY (im_in) * scale),
 108                         gdImageSX (im_in), gdImageSY (im_in));
 109   /* Write PNG */
 110   out = fopen (filename, "wb");
 111 
 112   /* If this image is the result of alpha channel blending,
 113      it will not contain an interesting alpha channel itself.
 114      Save a little file size by not saving the alpha channel.
 115      Otherwise the file would typically be slightly larger. */
 116   gdImageSaveAlpha (im_out, !blending);
 117 
 118   /* If requested, convert from truecolor to palette. */
 119   if (palette)
 120     {
 121       /* Dithering, 256 colors. */
 122       gdImageTrueColorToPalette (im_out, 1, 256);
 123     }
 124 
 125   gdImagePng (im_out, out);
 126   fclose (out);
 127 
 128   gdImageDestroy (im_out);
 129 }