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Lossless conversion for webp #7348

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Lossless conversion for webp #7348

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924c41a
Lossless conversion for webp
morsssss Aug 6, 2021
337afb4
Created IMG_WEBP_LOSSLESS constant
morsssss Aug 11, 2021
eab1110
Guard against older versions of gd that lack gdWebpLossless
morsssss Aug 12, 2021
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2 changes: 1 addition & 1 deletion ext/gd/config.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -92,7 +92,7 @@ AC_DEFUN([PHP_GD_AVIF],[

AC_DEFUN([PHP_GD_WEBP],[
if test "$PHP_WEBP" != "no"; then
PKG_CHECK_MODULES([WEBP], [libwebp])
PKG_CHECK_MODULES([WEBP], [libwebp >= 0.2.0])
PHP_EVAL_LIBLINE($WEBP_LIBS, GD_SHARED_LIBADD)
PHP_EVAL_INCLINE($WEBP_CFLAGS)
AC_DEFINE(HAVE_LIBWEBP, 1, [ ])
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3 changes: 3 additions & 0 deletions ext/gd/gd.c
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Expand Up @@ -378,6 +378,9 @@ PHP_MINIT_FUNCTION(gd)
REGISTER_LONG_CONSTANT("IMG_BMP", PHP_IMG_BMP, CONST_CS | CONST_PERSISTENT);
REGISTER_LONG_CONSTANT("IMG_TGA", PHP_IMG_TGA, CONST_CS | CONST_PERSISTENT);

/* constant for webp encoding */
REGISTER_LONG_CONSTANT("IMG_WEBP_LOSSLESS", PHP_IMG_WEBP_LOSSLESS, CONST_CS | CONST_PERSISTENT);

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What happens if ext/gd is compiled against a libgd which does not support lossless WebP encoding? Furthermore, there is currently no way to detect whether it is supported. So maybe:

Suggested change
/* constant for webp encoding */
REGISTER_LONG_CONSTANT("IMG_WEBP_LOSSLESS", PHP_IMG_WEBP_LOSSLESS, CONST_CS | CONST_PERSISTENT);
#ifdef gdWebpLossless
/* constant for webp encoding */
REGISTER_LONG_CONSTANT("IMG_WEBP_LOSSLESS", gdWebpLossless, CONST_CS | CONST_PERSISTENT);
#endif

(and ditch the definition of PHP_IMG_WEBP_LOSSLESS)

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I think I get it. Going forward, libgd will require a version of libwebp that's recent enough to support lossless WebP encoding. But your concern is that someone might use an older version of libgd. That older version wouldn't support losselss WebP... but it also wouldn't have the new gdWebpLossless defined.

If I'm getting that right, I think this solution is pretty clever.

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That older version wouldn't support losselss WebP... but it also wouldn't have the new gdWebpLossless defined.

Right.

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Now I see precedent for this in the code:

#ifdef gdEffectMultiply
	REGISTER_LONG_CONSTANT("IMG_EFFECT_MULTIPLY", gdEffectMultiply, CONST_CS | CONST_PERSISTENT);
#endif

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Interesting! gdEffectMultiply is defined as of libgd 2.1.1, but we're still supporting 2.1.0. Still, something that can be removed sometime in the future.

/* special colours for gd */
REGISTER_LONG_CONSTANT("IMG_COLOR_TILED", gdTiled, CONST_CS | CONST_PERSISTENT);
REGISTER_LONG_CONSTANT("IMG_COLOR_STYLED", gdStyled, CONST_CS | CONST_PERSISTENT);
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15 changes: 14 additions & 1 deletion ext/gd/libgd/gd.h
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Expand Up @@ -619,7 +619,20 @@ void *gdImageWBMPPtr(gdImagePtr im, int *size, int fg);
void gdImageJpeg(gdImagePtr im, FILE *out, int quality);
void gdImageJpegCtx(gdImagePtr im, gdIOCtx *out, int quality);

void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quantization);
/**
* Group: WebP
*
* Constant: gdWebpLossless
*
* Lossless quality threshold. When image quality is greater than or equal to
* <gdWebpLossless>, the image will be written in the lossless WebP format.
*
* See also:
* - <gdImageWebpCtx>
*/
#define gdWebpLossless 101

void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quality);

/* Best to free this memory with gdFree(), not free() */
void *gdImageJpegPtr(gdImagePtr im, int *size, int quality);
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22 changes: 14 additions & 8 deletions ext/gd/libgd/gd_webp.c
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Expand Up @@ -100,7 +100,7 @@ gdImagePtr gdImageCreateFromWebpCtx (gdIOCtx * infile)
return im;
}

void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quantization)
void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quality)
{
uint8_t *argb;
int x, y;
Expand All @@ -117,8 +117,8 @@ void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quantization)
return;
}

if (quantization == -1) {
quantization = 80;
if (quality == -1) {
quality = 80;
}

if (overflow2(gdImageSX(im), 4)) {
Expand Down Expand Up @@ -151,7 +151,13 @@ void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quantization)
*(p++) = a;
}
}
out_size = WebPEncodeRGBA(argb, gdImageSX(im), gdImageSY(im), gdImageSX(im) * 4, quantization, &out);

if (quality >= gdWebpLossless) {
out_size = WebPEncodeLosslessRGBA(argb, gdImageSX(im), gdImageSY(im), gdImageSX(im) * 4, &out);
} else {
out_size = WebPEncodeRGBA(argb, gdImageSX(im), gdImageSY(im), gdImageSX(im) * 4, quality, &out);
}

if (out_size == 0) {
zend_error(E_ERROR, "gd-webp encoding failed");
goto freeargb;
Expand All @@ -163,10 +169,10 @@ void gdImageWebpCtx (gdImagePtr im, gdIOCtx * outfile, int quantization)
gdFree(argb);
}

void gdImageWebpEx (gdImagePtr im, FILE * outFile, int quantization)
void gdImageWebpEx (gdImagePtr im, FILE * outFile, int quality)
{
gdIOCtx *out = gdNewFileCtx(outFile);
gdImageWebpCtx(im, out, quantization);
gdImageWebpCtx(im, out, quality);
out->gd_free(out);
}

Expand All @@ -188,11 +194,11 @@ void * gdImageWebpPtr (gdImagePtr im, int *size)
return rv;
}

void * gdImageWebpPtrEx (gdImagePtr im, int *size, int quantization)
void * gdImageWebpPtrEx (gdImagePtr im, int *size, int quality)
{
void *rv;
gdIOCtx *out = gdNewDynamicCtx(2048, NULL);
gdImageWebpCtx(im, out, quantization);
gdImageWebpCtx(im, out, quality);
rv = gdDPExtractData(out, size);
out->gd_free(out);
return rv;
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3 changes: 3 additions & 0 deletions ext/gd/php_gd.h
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Expand Up @@ -55,6 +55,9 @@
#define PHP_IMG_TGA 128
#define PHP_IMG_AVIF 256

/* constant for webp encoding. Matches gdWebpLossless in gd.h */
#define PHP_IMG_WEBP_LOSSLESS 101

#ifdef PHP_WIN32
# ifdef PHP_GD_EXPORTS
# define PHP_GD_API __declspec(dllexport)
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10 changes: 9 additions & 1 deletion ext/gd/tests/webp_basic.phpt
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Expand Up @@ -29,11 +29,19 @@ imagewebp($im1, $filename);

$im2 = imagecreatefromwebp($filename);
imagewebp($im2, $filename);
echo 'Is lossy conversion close enough? ';
var_dump(calc_image_dissimilarity($im1, $im2) < 10e5);

imagewebp($im1, $filename, IMG_WEBP_LOSSLESS);
$im_lossless = imagecreatefromwebp($filename);
echo 'Does lossless conversion work? ';
var_dump(calc_image_dissimilarity($im1, $im_lossless) == 0);

?>
--CLEAN--
<?php
@unlink(__DIR__ . '/webp_basic.webp');
?>
--EXPECT--
bool(true)
Is lossy conversion close enough? bool(true)
Does lossless conversion work? bool(true)