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[libpng16] Changed ICC profile support to allow use of an external color

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management system (CMS). In practice it is not possible to obtain cHRM
information reliably using just the end-point tags because they do not exist
in the vast majority of profiles.  Instead it is necessary to run the endpoints
through the ICC colorimetric intent transform (as described in the v4
spec).  Since this is likely to be too much code inside libpng for too
little gain (it implies a fairly complete CMS implementation) the code
has been changed to allow an external CMS to be used.  This code is
temporarily disabled until a suitable set of test cases using one or more
external CMS implementations have been implemented.
This commit is contained in:
John Bowler
2012-10-25 19:30:02 -05:00
committed by Glenn Randers-Pehrson
parent e6b710cb3f
commit f8dfd123e2
14 changed files with 821 additions and 944 deletions
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60
pngset.c
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@@ -143,25 +143,8 @@ png_set_gAMA_fixed(png_const_structrp png_ptr, png_inforp info_ptr,
if (png_ptr == NULL || info_ptr == NULL)
return;
/* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
* occur. Since the fixed point representation is assymetrical it is
* possible for 1/gamma to overflow the limit of 21474 and this means the
* gamma value must be at least 5/100000 and hence at most 20000.0. For
* safety the limits here are a little narrower. The values are 0.00016 to
* 6250.0, which are truly ridiculous gamma values (and will produce
* displays that are all black or all white.)
*/
if (file_gamma < 16 || file_gamma > 625000000)
png_app_error(png_ptr, "Out of range gamma value ignored");
else
{
if (png_colorspace_set_gamma(png_ptr, &info_ptr->colorspace, file_gamma,
2/* overrided with app value */))
info_ptr->colorspace.flags |= PNG_COLORSPACE_FROM_gAMA;
png_colorspace_sync_info(png_ptr, info_ptr);
}
png_colorspace_set_gamma(png_ptr, &info_ptr->colorspace, file_gamma);
png_colorspace_sync_info(png_ptr, info_ptr);
}
# ifdef PNG_FLOATING_POINT_SUPPORTED
@@ -595,9 +578,7 @@ png_set_sRGB(png_const_structrp png_ptr, png_inforp info_ptr, int srgb_intent)
if (png_ptr == NULL || info_ptr == NULL)
return;
(void)png_colorspace_set_sRGB(png_ptr, &info_ptr->colorspace, srgb_intent,
2/* app value overrides*/);
png_colorspace_set_sRGB(png_ptr, &info_ptr->colorspace, srgb_intent);
png_colorspace_sync_info(png_ptr, info_ptr);
}
@@ -610,10 +591,9 @@ png_set_sRGB_gAMA_and_cHRM(png_const_structrp png_ptr, png_inforp info_ptr,
if (png_ptr == NULL || info_ptr == NULL)
return;
if (png_colorspace_set_sRGB(png_ptr, &info_ptr->colorspace, srgb_intent,
2/* app value overrides*/))
if (png_colorspace_set_sRGB(png_ptr, &info_ptr->colorspace, srgb_intent))
{
/* And cause the gAMA and cHRM to be written too */
/* This causes the gAMA and cHRM to be written too */
info_ptr->colorspace.flags |=
PNG_COLORSPACE_FROM_gAMA|PNG_COLORSPACE_FROM_cHRM;
}
@@ -1570,4 +1550,34 @@ png_set_check_for_invalid_index(png_structrp png_ptr, int allowed)
}
#endif
#ifdef PNG_ICC_SUPPORTED
void PNGAPI
png_set_cms(png_structrp png_ptr, png_cms_datap cms_data_ptr,
png_cms_transform_ptr cms_transform_function)
{
png_ptr->cms_transform_fn = cms_transform_function;
png_ptr->cms_data_ptr = cms_data_ptr;
}
#ifdef PNG_READ_SUPPORTED
void PNGAPI
png_set_cms_output(png_structrp png_ptr, int bytes_per_pixel,
int rendering_intent)
{
if (png_ptr->mode & PNG_IS_READ_STRUCT)
{
png_ptr->cms_bytes_per_pixel = bytes_per_pixel;
png_ptr->cms_intent = rendering_intent;
/* A CMS must be registered before calling this */
if (png_ptr->cms_transform_fn == NULL)
png_app_error(png_ptr, "no CMS registered to transform output");
}
else
png_app_error(png_ptr, "attempt to do CMS tranform on write");
}
#endif /* PNG_READ_SUPPORTED */
#endif /* PNG_ICC_SUPPORTED */
#endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */