119 lines
4.0 KiB
C
119 lines
4.0 KiB
C
#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include "gd.h"
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/* If palette is true, we convert from truecolor to palette at the end,
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to test gdImageTrueColorToPalette and see file size/
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quality tradeoffs. */
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void testDrawing (gdImagePtr im_in,
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double scale, int blending, int palette, char *filename);
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int
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main (int argc, char *argv[])
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{
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/* Input and output files */
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FILE *in;
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/* Input image */
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gdImagePtr im_in = 0;
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if (argc != 2) {
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fprintf (stderr, "Usage: testac filename.png\n");
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exit (1);
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}
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/* Load original PNG, which should contain alpha channel
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information. We will use it in two ways: preserving it
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literally, for use with compatible browsers, and
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compositing it ourselves against a background of our
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choosing (alpha blending). We'll change its size
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and try creating palette versions of it. */
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in = fopen (argv[1], "rb");
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if (!in) {
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fprintf (stderr, "Can't load %s.\n", argv[1]);
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exit (1);
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} else {
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im_in = gdImageCreateFromPng (in);
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fclose (in);
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}
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testDrawing (im_in, 1.0, 0, 0, "noblending-fullsize-truecolor.png");
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testDrawing (im_in, 1.0, 1, 0, "blending-fullsize-truecolor.png");
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testDrawing (im_in, 0.5, 0, 0, "noblending-halfsize-truecolor.png");
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testDrawing (im_in, 0.5, 1, 0, "blending-halfsize-truecolor.png");
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testDrawing (im_in, 2.0, 0, 0, "noblending-doublesize-truecolor.png");
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testDrawing (im_in, 2.0, 1, 0, "blending-doublesize-truecolor.png");
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testDrawing (im_in, 1.0, 0, 1, "noblending-fullsize-palette.png");
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testDrawing (im_in, 1.0, 1, 1, "blending-fullsize-palette.png");
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testDrawing (im_in, 0.5, 0, 1, "noblending-halfsize-palette.png");
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testDrawing (im_in, 0.5, 1, 1, "blending-halfsize-palette.png");
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testDrawing (im_in, 2.0, 0, 1, "noblending-doublesize-palette.png");
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testDrawing (im_in, 2.0, 1, 1, "blending-doublesize-palette.png");
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gdImageDestroy (im_in);
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return 0;
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}
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/* If palette is true, we convert from truecolor to palette at the end,
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to test gdImageTrueColorToPalette and see file size/
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quality tradeoffs. */
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void
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testDrawing (gdImagePtr im_in,
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double scale, int blending, int palette, char *filename)
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{
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gdImagePtr im_out;
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FILE *out;
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/* Create output image. */
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im_out = gdImageCreateTrueColor ((int) (gdImageSX (im_in) * scale),
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(int) (gdImageSY (im_in) * scale));
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/*
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Request alpha blending. This causes future
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drawing operations to perform alpha channel blending
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with the background, resulting in an opaque image.
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Without this call, pixels in the foreground color are
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copied literally, *including* the alpha channel value,
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resulting in an output image which is potentially
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not opaque. This flag can be set and cleared as often
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as desired. */
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gdImageAlphaBlending (im_out, blending);
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/* Flood with light blue. */
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gdImageFill (im_out, (int) (gdImageSX (im_in) * scale / 2),
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(int) (gdImageSY (im_in) * scale / 2),
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gdTrueColor (192, 192, 255));
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/* Copy the source image. Alpha blending should result in
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compositing against red. With blending turned off, the
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browser or viewer will composite against its preferred
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background, or, if it does not support an alpha channel,
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we will see the original colors for the pixels that
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ought to be transparent or semitransparent. */
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gdImageCopyResampled (im_out, im_in,
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0, 0,
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0, 0,
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(int) (gdImageSX (im_in) * scale),
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(int) (gdImageSY (im_in) * scale), gdImageSX (im_in),
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gdImageSY (im_in));
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/* Write PNG */
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out = fopen (filename, "wb");
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/* If this image is the result of alpha channel blending,
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it will not contain an interesting alpha channel itself.
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Save a little file size by not saving the alpha channel.
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Otherwise the file would typically be slightly larger. */
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gdImageSaveAlpha (im_out, !blending);
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/* If requested, convert from truecolor to palette. */
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if (palette) {
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/* Dithering, 256 colors. */
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gdImageTrueColorToPalette (im_out, 1, 256);
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}
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gdImagePng (im_out, out);
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fclose (out);
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gdImageDestroy (im_out);
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}
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