Skip to content

Commit

Permalink
PNGv3 colourspace precedence rules conformance
Browse files Browse the repository at this point in the history 
This is a major change required by the new PNGv3 colour chunk precedence
rules.  It **does not** change the libpng API (png.h) however it changes
the following handling of PNG files:

IFF the PNG file contains colour space information it changes from the
libpng v3 behaviour to the now compulsory PNG v3 behaviour:

1) libpng no longer invalidates colour space chunks because they are
   inconsistent.
2) libpng no longer responds to the "png_get_" APIs positively if they
   are not present in the PNG but can be deduced from the colour space
   chunks that are present.
  • Loading branch information
@jbowler
jbowler committed Jan 26, 2025
1 parent 0024abd commit 34f3090
Show file tree
Hide file tree
Showing 12 changed files with 1,737 additions and 2,863 deletions.
1,119 changes: 233 additions & 886 deletions png.c
View file

Large diffs are not rendered by default.

178 changes: 76 additions & 102 deletions pngget.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -380,7 +380,13 @@ png_fixed_inches_from_microns(png_const_structrp png_ptr, png_int_32 microns)
* Notice that this can overflow - a warning is output and 0 is
* returned.
*/
return png_muldiv_warn(png_ptr, microns, 500, 127);
png_fixed_point result;

if (png_muldiv(&result, microns, 500, 127) != 0)
return result;

png_warning(png_ptr, "fixed point overflow ignored");
return 0;
}

png_fixed_point PNGAPI
Expand All @@ -390,7 +396,7 @@ png_get_x_offset_inches_fixed(png_const_structrp png_ptr,
return png_fixed_inches_from_microns(png_ptr,
png_get_x_offset_microns(png_ptr, info_ptr));
}
#endif
#endif /* FIXED_POINT */

#ifdef PNG_FIXED_POINT_SUPPORTED
png_fixed_point PNGAPI
Expand Down Expand Up @@ -518,44 +524,31 @@ png_get_bKGD(png_const_structrp png_ptr, png_inforp info_ptr,
# ifdef PNG_FLOATING_POINT_SUPPORTED
png_uint_32 PNGAPI
png_get_cHRM(png_const_structrp png_ptr, png_const_inforp info_ptr,
double *white_x, double *white_y, double *red_x, double *red_y,
double *green_x, double *green_y, double *blue_x, double *blue_y)
double *whitex, double *whitey, double *redx, double *redy,
double *greenx, double *greeny, double *bluex, double *bluey)
{
png_debug1(1, "in %s retrieval function", "cHRM");

/* Quiet API change: this code used to only return the end points if a cHRM
* chunk was present, but the end points can also come from iCCP or sRGB
* chunks, so in 1.6.0 the png_get_ APIs return the end points regardless and
* the png_set_ APIs merely check that set end points are mutually
* consistent.
*/
/* PNGv3: this just returns the values store from the cHRM, if any. */
if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
(info_ptr->valid & PNG_INFO_cHRM) != 0)
{
if (white_x != NULL)
*white_x = png_float(png_ptr,
info_ptr->colorspace.end_points_xy.whitex, "cHRM white X");
if (white_y != NULL)
*white_y = png_float(png_ptr,
info_ptr->colorspace.end_points_xy.whitey, "cHRM white Y");
if (red_x != NULL)
*red_x = png_float(png_ptr, info_ptr->colorspace.end_points_xy.redx,
"cHRM red X");
if (red_y != NULL)
*red_y = png_float(png_ptr, info_ptr->colorspace.end_points_xy.redy,
"cHRM red Y");
if (green_x != NULL)
*green_x = png_float(png_ptr,
info_ptr->colorspace.end_points_xy.greenx, "cHRM green X");
if (green_y != NULL)
*green_y = png_float(png_ptr,
info_ptr->colorspace.end_points_xy.greeny, "cHRM green Y");
if (blue_x != NULL)
*blue_x = png_float(png_ptr, info_ptr->colorspace.end_points_xy.bluex,
"cHRM blue X");
if (blue_y != NULL)
*blue_y = png_float(png_ptr, info_ptr->colorspace.end_points_xy.bluey,
"cHRM blue Y");
if (whitex != NULL)
*whitex = png_float(png_ptr, info_ptr->cHRM.whitex, "cHRM wx");
if (whitey != NULL)
*whitey = png_float(png_ptr, info_ptr->cHRM.whitey, "cHRM wy");
if (redx != NULL)
*redx = png_float(png_ptr, info_ptr->cHRM.redx, "cHRM rx");
if (redy != NULL)
*redy = png_float(png_ptr, info_ptr->cHRM.redy, "cHRM ry");
if (greenx != NULL)
*greenx = png_float(png_ptr, info_ptr->cHRM.greenx, "cHRM gx");
if (greeny != NULL)
*greeny = png_float(png_ptr, info_ptr->cHRM.greeny, "cHRM gy");
if (bluex != NULL)
*bluex = png_float(png_ptr, info_ptr->cHRM.bluex, "cHRM bx");
if (bluey != NULL)
*bluey = png_float(png_ptr, info_ptr->cHRM.bluey, "cHRM by");
return PNG_INFO_cHRM;
}

Expand All @@ -568,38 +561,31 @@ png_get_cHRM_XYZ(png_const_structrp png_ptr, png_const_inforp info_ptr,
double *green_Y, double *green_Z, double *blue_X, double *blue_Y,
double *blue_Z)
{
png_XYZ XYZ;
png_debug1(1, "in %s retrieval function", "cHRM_XYZ(float)");

if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
(info_ptr->valid & PNG_INFO_cHRM) != 0 &&
png_XYZ_from_xy(&XYZ, &info_ptr->cHRM) == 0)
{
if (red_X != NULL)
*red_X = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_X,
"cHRM red X");
*red_X = png_float(png_ptr, XYZ.red_X, "cHRM red X");
if (red_Y != NULL)
*red_Y = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_Y,
"cHRM red Y");
*red_Y = png_float(png_ptr, XYZ.red_Y, "cHRM red Y");
if (red_Z != NULL)
*red_Z = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_Z,
"cHRM red Z");
*red_Z = png_float(png_ptr, XYZ.red_Z, "cHRM red Z");
if (green_X != NULL)
*green_X = png_float(png_ptr,
info_ptr->colorspace.end_points_XYZ.green_X, "cHRM green X");
*green_X = png_float(png_ptr, XYZ.green_X, "cHRM green X");
if (green_Y != NULL)
*green_Y = png_float(png_ptr,
info_ptr->colorspace.end_points_XYZ.green_Y, "cHRM green Y");
*green_Y = png_float(png_ptr, XYZ.green_Y, "cHRM green Y");
if (green_Z != NULL)
*green_Z = png_float(png_ptr,
info_ptr->colorspace.end_points_XYZ.green_Z, "cHRM green Z");
*green_Z = png_float(png_ptr, XYZ.green_Z, "cHRM green Z");
if (blue_X != NULL)
*blue_X = png_float(png_ptr,
info_ptr->colorspace.end_points_XYZ.blue_X, "cHRM blue X");
*blue_X = png_float(png_ptr, XYZ.blue_X, "cHRM blue X");
if (blue_Y != NULL)
*blue_Y = png_float(png_ptr,
info_ptr->colorspace.end_points_XYZ.blue_Y, "cHRM blue Y");
*blue_Y = png_float(png_ptr, XYZ.blue_Y, "cHRM blue Y");
if (blue_Z != NULL)
*blue_Z = png_float(png_ptr,
info_ptr->colorspace.end_points_XYZ.blue_Z, "cHRM blue Z");
*blue_Z = png_float(png_ptr, XYZ.blue_Z, "cHRM blue Z");
return PNG_INFO_cHRM;
}

Expand All @@ -616,29 +602,22 @@ png_get_cHRM_XYZ_fixed(png_const_structrp png_ptr, png_const_inforp info_ptr,
png_fixed_point *int_blue_X, png_fixed_point *int_blue_Y,
png_fixed_point *int_blue_Z)
{
png_XYZ XYZ;
png_debug1(1, "in %s retrieval function", "cHRM_XYZ");

if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
(info_ptr->valid & PNG_INFO_cHRM) != 0U &&
png_XYZ_from_xy(&XYZ, &info_ptr->cHRM) == 0)
{
if (int_red_X != NULL)
*int_red_X = info_ptr->colorspace.end_points_XYZ.red_X;
if (int_red_Y != NULL)
*int_red_Y = info_ptr->colorspace.end_points_XYZ.red_Y;
if (int_red_Z != NULL)
*int_red_Z = info_ptr->colorspace.end_points_XYZ.red_Z;
if (int_green_X != NULL)
*int_green_X = info_ptr->colorspace.end_points_XYZ.green_X;
if (int_green_Y != NULL)
*int_green_Y = info_ptr->colorspace.end_points_XYZ.green_Y;
if (int_green_Z != NULL)
*int_green_Z = info_ptr->colorspace.end_points_XYZ.green_Z;
if (int_blue_X != NULL)
*int_blue_X = info_ptr->colorspace.end_points_XYZ.blue_X;
if (int_blue_Y != NULL)
*int_blue_Y = info_ptr->colorspace.end_points_XYZ.blue_Y;
if (int_blue_Z != NULL)
*int_blue_Z = info_ptr->colorspace.end_points_XYZ.blue_Z;
if (int_red_X != NULL) *int_red_X = XYZ.red_X;
if (int_red_Y != NULL) *int_red_Y = XYZ.red_Y;
if (int_red_Z != NULL) *int_red_Z = XYZ.red_Z;
if (int_green_X != NULL) *int_green_X = XYZ.green_X;
if (int_green_Y != NULL) *int_green_Y = XYZ.green_Y;
if (int_green_Z != NULL) *int_green_Z = XYZ.green_Z;
if (int_blue_X != NULL) *int_blue_X = XYZ.blue_X;
if (int_blue_Y != NULL) *int_blue_Y = XYZ.blue_Y;
if (int_blue_Z != NULL) *int_blue_Z = XYZ.blue_Z;
return PNG_INFO_cHRM;
}

Expand All @@ -647,31 +626,24 @@ png_get_cHRM_XYZ_fixed(png_const_structrp png_ptr, png_const_inforp info_ptr,

png_uint_32 PNGAPI
png_get_cHRM_fixed(png_const_structrp png_ptr, png_const_inforp info_ptr,
png_fixed_point *white_x, png_fixed_point *white_y, png_fixed_point *red_x,
png_fixed_point *red_y, png_fixed_point *green_x, png_fixed_point *green_y,
png_fixed_point *blue_x, png_fixed_point *blue_y)
png_fixed_point *whitex, png_fixed_point *whitey, png_fixed_point *redx,
png_fixed_point *redy, png_fixed_point *greenx, png_fixed_point *greeny,
png_fixed_point *bluex, png_fixed_point *bluey)
{
png_debug1(1, "in %s retrieval function", "cHRM");

/* PNGv3: this just returns the values store from the cHRM, if any. */
if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
(info_ptr->valid & PNG_INFO_cHRM) != 0)
{
if (white_x != NULL)
*white_x = info_ptr->colorspace.end_points_xy.whitex;
if (white_y != NULL)
*white_y = info_ptr->colorspace.end_points_xy.whitey;
if (red_x != NULL)
*red_x = info_ptr->colorspace.end_points_xy.redx;
if (red_y != NULL)
*red_y = info_ptr->colorspace.end_points_xy.redy;
if (green_x != NULL)
*green_x = info_ptr->colorspace.end_points_xy.greenx;
if (green_y != NULL)
*green_y = info_ptr->colorspace.end_points_xy.greeny;
if (blue_x != NULL)
*blue_x = info_ptr->colorspace.end_points_xy.bluex;
if (blue_y != NULL)
*blue_y = info_ptr->colorspace.end_points_xy.bluey;
if (whitex != NULL) *whitex = info_ptr->cHRM.whitex;
if (whitey != NULL) *whitey = info_ptr->cHRM.whitey;
if (redx != NULL) *redx = info_ptr->cHRM.redx;
if (redy != NULL) *redy = info_ptr->cHRM.redy;
if (greenx != NULL) *greenx = info_ptr->cHRM.greenx;
if (greeny != NULL) *greeny = info_ptr->cHRM.greeny;
if (bluex != NULL) *bluex = info_ptr->cHRM.bluex;
if (bluey != NULL) *bluey = info_ptr->cHRM.bluey;
return PNG_INFO_cHRM;
}

Expand All @@ -688,11 +660,11 @@ png_get_gAMA_fixed(png_const_structrp png_ptr, png_const_inforp info_ptr,
{
png_debug1(1, "in %s retrieval function", "gAMA");

/* PNGv3 compatibility: only report gAMA if it is really present. */
if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
file_gamma != NULL)
(info_ptr->valid & PNG_INFO_gAMA) != 0)
{
*file_gamma = info_ptr->colorspace.gamma;
if (file_gamma != NULL) *file_gamma = info_ptr->gamma;
return PNG_INFO_gAMA;
}

Expand All @@ -707,12 +679,13 @@ png_get_gAMA(png_const_structrp png_ptr, png_const_inforp info_ptr,
{
png_debug1(1, "in %s retrieval function", "gAMA(float)");

/* PNGv3 compatibility: only report gAMA if it is really present. */
if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
file_gamma != NULL)
(info_ptr->valid & PNG_INFO_gAMA) != 0)
{
*file_gamma = png_float(png_ptr, info_ptr->colorspace.gamma,
"png_get_gAMA");
if (file_gamma != NULL)
*file_gamma = png_float(png_ptr, info_ptr->gamma, "gAMA");

return PNG_INFO_gAMA;
}

Expand All @@ -729,9 +702,10 @@ png_get_sRGB(png_const_structrp png_ptr, png_const_inforp info_ptr,
png_debug1(1, "in %s retrieval function", "sRGB");

if (png_ptr != NULL && info_ptr != NULL &&
(info_ptr->valid & PNG_INFO_sRGB) != 0 && file_srgb_intent != NULL)
(info_ptr->valid & PNG_INFO_sRGB) != 0)
{
*file_srgb_intent = info_ptr->colorspace.rendering_intent;
if (file_srgb_intent != NULL)
*file_srgb_intent = info_ptr->rendering_intent;
return PNG_INFO_sRGB;
}

Expand Down
30 changes: 12 additions & 18 deletions pnginfo.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -86,20 +86,6 @@ struct png_info_def
* and initialize the appropriate fields below.
*/

#if defined(PNG_COLORSPACE_SUPPORTED) || defined(PNG_GAMMA_SUPPORTED)
/* png_colorspace only contains 'flags' if neither GAMMA or COLORSPACE are
* defined. When COLORSPACE is switched on all the colorspace-defining
* chunks should be enabled, when GAMMA is switched on all the gamma-defining
* chunks should be enabled. If this is not done it becomes possible to read
* inconsistent PNG files and assign a probably incorrect interpretation to
* the information. (In other words, by carefully choosing which chunks to
* recognize the system configuration can select an interpretation for PNG
* files containing ambiguous data and this will result in inconsistent
* behavior between different libpng builds!)
*/
png_colorspace colorspace;
#endif

#ifdef PNG_cICP_SUPPORTED
/* cICP chunk data */
png_byte cicp_colour_primaries;
Expand Down Expand Up @@ -211,11 +197,8 @@ defined(PNG_READ_BACKGROUND_SUPPORTED)
#endif

#ifdef PNG_eXIf_SUPPORTED
int num_exif; /* Added at libpng-1.6.31 */
png_uint_32 num_exif; /* Added at libpng-1.6.31 */
png_bytep exif;
# ifdef PNG_READ_eXIf_SUPPORTED
png_bytep eXIf_buf; /* Added at libpng-1.6.32 */
# endif
#endif

#ifdef PNG_hIST_SUPPORTED
Expand Down Expand Up @@ -288,5 +271,16 @@ defined(PNG_READ_BACKGROUND_SUPPORTED)
png_bytepp row_pointers; /* the image bits */
#endif

#ifdef PNG_cHRM_SUPPORTED
png_xy cHRM;
#endif

#ifdef PNG_gAMA_SUPPORTED
png_fixed_point gamma;
#endif

#ifdef PNG_sRGB_SUPPORTED
int rendering_intent;
#endif
};
#endif /* PNGINFO_H */
Loading

0 comments on commit 34f3090

Please sign in to comment.