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Back-port pngvalid corrections and enhancements

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This is a patch for libpng16.
It incorporates fixes to the low-bit-depth gray background handling from
libpng17 and turns one of the low-bit-depth gray cases that does work (and,
indeed, did work before) in libpng16

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler 2015-09-17 07:56:30 -07:00
parent c3e7e7d715
commit e8c554661c
1 changed files with 17 additions and 14 deletions
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31
contrib/libtests/pngvalid.c
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@ -5408,7 +5408,7 @@ test_size(png_modifier* const pm, png_byte const colour_type,
# ifdef PNG_READ_DEINTERLACE_SUPPORTED # ifdef PNG_READ_DEINTERLACE_SUPPORTED
# ifdef PNG_WRITE_INTERLACING_SUPPORTED # ifdef PNG_WRITE_INTERLACING_SUPPORTED
/* Test both togeher: */ /* Test both together: */
standard_test(&pm->this, FILEID(colour_type, DEPTH(bdlo), 0/*palette*/, standard_test(&pm->this, FILEID(colour_type, DEPTH(bdlo), 0/*palette*/,
PNG_INTERLACE_ADAM7, w, h, 0), 0/*do_interlace*/, PNG_INTERLACE_ADAM7, w, h, 0), 0/*do_interlace*/,
pm->use_update_info); pm->use_update_info);
@ -5661,10 +5661,13 @@ image_pixel_convert_PLTE(image_pixel *this)
/* Add an alpha channel; this will import the tRNS information because tRNS is /* Add an alpha channel; this will import the tRNS information because tRNS is
* not valid in an alpha image. The bit depth will invariably be set to at * not valid in an alpha image. The bit depth will invariably be set to at
* least 8 prior to 1.7.0. Palette images will be converted to alpha (using * least 8 prior to 1.7.0. Palette images will be converted to alpha (using
* the above API). * the above API). With png_set_background the alpha channel is never expanded
* but this routine is used by pngvalid to simplify code; 'for_background'
* records this.
*/ */
static void static void
image_pixel_add_alpha(image_pixel *this, const standard_display *display) image_pixel_add_alpha(image_pixel *this, const standard_display *display,
int for_background)
{ {
if (this->colour_type == PNG_COLOR_TYPE_PALETTE) if (this->colour_type == PNG_COLOR_TYPE_PALETTE)
image_pixel_convert_PLTE(this); image_pixel_convert_PLTE(this);
@ -5674,7 +5677,7 @@ image_pixel_add_alpha(image_pixel *this, const standard_display *display)
if (this->colour_type == PNG_COLOR_TYPE_GRAY) if (this->colour_type == PNG_COLOR_TYPE_GRAY)
{ {
# if PNG_LIBPNG_VER < 10700 # if PNG_LIBPNG_VER < 10700
if (this->bit_depth < 8) if (!for_background && this->bit_depth < 8)
this->bit_depth = this->sample_depth = 8; this->bit_depth = this->sample_depth = 8;
# endif # endif
@ -5684,7 +5687,7 @@ image_pixel_add_alpha(image_pixel *this, const standard_display *display)
* tRNS chunk to expand at this point. * tRNS chunk to expand at this point.
*/ */
# if PNG_LIBPNG_VER >= 10700 # if PNG_LIBPNG_VER >= 10700
if (this->bit_depth < 8) if (!for_background && this->bit_depth < 8)
this->bit_depth = this->sample_depth = 8; this->bit_depth = this->sample_depth = 8;
# endif # endif
@ -6574,7 +6577,7 @@ image_transform_png_set_tRNS_to_alpha_mod(const image_transform *this,
if (that->colour_type != PNG_COLOR_TYPE_PALETTE && if (that->colour_type != PNG_COLOR_TYPE_PALETTE &&
(that->colour_type & PNG_COLOR_MASK_ALPHA) == 0) (that->colour_type & PNG_COLOR_MASK_ALPHA) == 0)
# endif # endif
image_pixel_add_alpha(that, &display->this); image_pixel_add_alpha(that, &display->this, 0/*!for background*/);
#if PNG_LIBPNG_VER < 10700 #if PNG_LIBPNG_VER < 10700
/* LIBPNG BUG: otherwise libpng still expands to 8 bits! */ /* LIBPNG BUG: otherwise libpng still expands to 8 bits! */
@ -6601,8 +6604,8 @@ image_transform_png_set_tRNS_to_alpha_add(image_transform *this,
/* We don't know yet whether there will be a tRNS chunk, but we know that /* We don't know yet whether there will be a tRNS chunk, but we know that
* this transformation should do nothing if there already is an alpha * this transformation should do nothing if there already is an alpha
* channel. In addition, afte the bug fix in 1.7.0, there is no longer any * channel. In addition, after the bug fix in 1.7.0, there is no longer
* action on a palette image. * any action on a palette image.
*/ */
return return
# if PNG_LIBPNG_VER >= 10700 # if PNG_LIBPNG_VER >= 10700
@ -6638,7 +6641,7 @@ image_transform_png_set_gray_to_rgb_mod(const image_transform *this,
* doesn't do this, so we don't either. * doesn't do this, so we don't either.
*/ */
if ((that->colour_type & PNG_COLOR_MASK_COLOR) == 0 && that->have_tRNS) if ((that->colour_type & PNG_COLOR_MASK_COLOR) == 0 && that->have_tRNS)
image_pixel_add_alpha(that, &display->this); image_pixel_add_alpha(that, &display->this, 0/*!for background*/);
/* Simply expand the bit depth and alter the colour type as required. */ /* Simply expand the bit depth and alter the colour type as required. */
if (that->colour_type == PNG_COLOR_TYPE_GRAY) if (that->colour_type == PNG_COLOR_TYPE_GRAY)
@ -6702,7 +6705,7 @@ image_transform_png_set_expand_mod(const image_transform *this,
that->sample_depth = that->bit_depth = 8; that->sample_depth = that->bit_depth = 8;
if (that->have_tRNS) if (that->have_tRNS)
image_pixel_add_alpha(that, &display->this); image_pixel_add_alpha(that, &display->this, 0/*!for background*/);
this->next->mod(this->next, that, pp, display); this->next->mod(this->next, that, pp, display);
} }
@ -6812,7 +6815,7 @@ image_transform_png_set_expand_16_mod(const image_transform *this,
image_pixel_convert_PLTE(that); image_pixel_convert_PLTE(that);
if (that->have_tRNS) if (that->have_tRNS)
image_pixel_add_alpha(that, &display->this); image_pixel_add_alpha(that, &display->this, 0/*!for background*/);
if (that->bit_depth < 16) if (that->bit_depth < 16)
that->sample_depth = that->bit_depth = 16; that->sample_depth = that->bit_depth = 16;
@ -7755,7 +7758,7 @@ image_transform_png_set_background_mod(const image_transform *this,
{ {
/* Check for tRNS first: */ /* Check for tRNS first: */
if (that->have_tRNS && that->colour_type != PNG_COLOR_TYPE_PALETTE) if (that->have_tRNS && that->colour_type != PNG_COLOR_TYPE_PALETTE)
image_pixel_add_alpha(that, &display->this); image_pixel_add_alpha(that, &display->this, 1/*for background*/);
/* This is only necessary if the alpha value is less than 1. */ /* This is only necessary if the alpha value is less than 1. */
if (that->alphaf < 1) if (that->alphaf < 1)
@ -11109,9 +11112,9 @@ int main(int argc, char **argv)
# endif # endif
pm.test_lbg = 0; pm.test_lbg = 0;
pm.test_lbg_gamma_threshold = 1; pm.test_lbg_gamma_threshold = 1;
pm.test_lbg_gamma_transform = 0/*PNG_LIBPNG_VER >= 10700*/; pm.test_lbg_gamma_transform = PNG_LIBPNG_VER >= 10600;
pm.test_lbg_gamma_sbit = 1; pm.test_lbg_gamma_sbit = 1;
pm.test_lbg_gamma_composition = 0; pm.test_lbg_gamma_composition = PNG_LIBPNG_VER >= 10700;
/* And the test encodings */ /* And the test encodings */
pm.encodings = test_encodings; pm.encodings = test_encodings;