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plug-ins: PNG export TRC chosen similarly to TIFF. 

While we tend to default to sRGB for 8-bit max formats (such as JPEG or
WebP) when no explicitly-assigned profile was set, there is no need to
do so for PNG too. Indeed since we have the ability to export 16-bit
PNG, let's consider this is ok to export 16-bit linear data when writing
GIMP's default linear profile.

Moreover let's follow the profile's (fallback to storage's) TRC also
when exporting to a specific precision (as chosen manually in the
dialog), not only when sticking to "Automatic", unless we are downsizing
a high bit depth work image to 8-bit without a manually assigned profile
(the only case we forcefully export as sRGB data, hence convert the
profile if linear storage).
This commit is contained in:
Jehan 2019-06-07 18:18:33 +02:00
parent 8cd3f5a853
commit 24ed5870ad
1 changed files with 73 additions and 28 deletions
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101
plug-ins/common/file-png.c
View File

@ -1494,27 +1494,47 @@ save_image (const gchar *filename,
out_linear = FALSE;
#if defined(PNG_iCCP_SUPPORTED)
profile = gimp_image_get_color_profile (orig_image_ID);
/* If no profile is written: export as sRGB.
* If manually assigned profile written: follow its TRC.
* If default profile written:
* - when export as auto or 16-bit: follow the storage TRC.
* - when export from 8-bit storage: follow the storage TRC.
* - when converting high bit depth to 8-bit: export as sRGB.
*/
if (pngvals.save_profile)
{
if (profile && gimp_color_profile_is_linear (profile) &&
pngvals.export_format == PNG_FORMAT_AUTO)
out_linear = TRUE;
profile = gimp_image_get_color_profile (orig_image_ID);
if (! profile)
profile = gimp_image_get_effective_color_profile (orig_image_ID);
if (! out_linear && gimp_color_profile_is_linear (profile))
if (profile ||
pngvals.export_format == PNG_FORMAT_AUTO ||
pngvals.export_format == PNG_FORMAT_RGB16 ||
pngvals.export_format == PNG_FORMAT_RGBA16 ||
pngvals.export_format == PNG_FORMAT_GRAY16 ||
pngvals.export_format == PNG_FORMAT_GRAYA16 ||
gimp_image_get_precision (image_ID) == GIMP_PRECISION_U8_LINEAR ||
gimp_image_get_precision (image_ID) == GIMP_PRECISION_U8_NON_LINEAR ||
gimp_image_get_precision (image_ID) == GIMP_PRECISION_U8_PERCEPTUAL)
{
/* This should happen only when using default linear profile
* (no profile explicitly set) or when not exporting to
* PNG_FORMAT_AUTO.
*/
GimpColorProfile *saved_profile;
if (! profile)
profile = gimp_image_get_effective_color_profile (orig_image_ID);
out_linear = (gimp_color_profile_is_linear (profile));
}
else
{
/* When converting higher bit depth work image into 8-bit,
* with no manually assigned profile, make sure the result if
* sRGB. */
profile = gimp_image_get_effective_color_profile (orig_image_ID);
if (gimp_color_profile_is_linear (profile))
{
GimpColorProfile *saved_profile;
saved_profile = gimp_color_profile_new_srgb_trc_from_color_profile (profile);
g_object_unref (profile);
profile = saved_profile;
}
saved_profile = gimp_color_profile_new_srgb_trc_from_color_profile (profile);
g_object_unref (profile);
profile = saved_profile;
}
}
#endif
@ -1534,7 +1554,8 @@ save_image (const gchar *filename,
case GIMP_PRECISION_U8_NON_LINEAR:
case GIMP_PRECISION_U8_PERCEPTUAL:
bit_depth = 8;
if (! out_linear)
bit_depth = 8;
break;
default:
@ -1718,45 +1739,70 @@ save_image (const gchar *filename,
{
case PNG_FORMAT_RGB8:
color_type = PNG_COLOR_TYPE_RGB;
file_format = babl_format ("R'G'B' u8");
if (out_linear)
file_format = babl_format ("RGB u8");
else
file_format = babl_format ("R'G'B' u8");
bit_depth = 8;
break;
case PNG_FORMAT_GRAY8:
color_type = PNG_COLOR_TYPE_GRAY;
file_format = babl_format ("Y' u8");
if (out_linear)
file_format = babl_format ("Y u8");
else
file_format = babl_format ("Y' u8");
bit_depth = 8;
break;
case PNG_FORMAT_AUTO: // shut up gcc
case PNG_FORMAT_RGBA8:
color_type = PNG_COLOR_TYPE_RGB_ALPHA;
file_format = babl_format ("R'G'B'A u8");
if (out_linear)
file_format = babl_format ("RGBA u8");
else
file_format = babl_format ("R'G'B'A u8");
bit_depth = 8;
break;
case PNG_FORMAT_GRAYA8:
color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
file_format = babl_format ("Y'A u8");
if (out_linear)
file_format = babl_format ("YA u8");
else
file_format = babl_format ("Y'A u8");
bit_depth = 8;
break;
case PNG_FORMAT_RGB16:
color_type = PNG_COLOR_TYPE_RGB;
file_format = babl_format ("R'G'B' u16");
if (out_linear)
file_format = babl_format ("RGB u16");
else
file_format = babl_format ("R'G'B' u16");
bit_depth = 16;
break;
case PNG_FORMAT_GRAY16:
color_type = PNG_COLOR_TYPE_GRAY;
file_format = babl_format ("Y' u16");
if (out_linear)
file_format = babl_format ("Y u16");
else
file_format = babl_format ("Y' u16");
bit_depth = 16;
break;
case PNG_FORMAT_RGBA16:
color_type = PNG_COLOR_TYPE_RGB_ALPHA;
file_format = babl_format ("R'G'B'A u16");
if (out_linear)
file_format = babl_format ("RGBA u16");
else
file_format = babl_format ("R'G'B'A u16");
bit_depth = 16;
break;
case PNG_FORMAT_GRAYA16:
color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
file_format = babl_format ("Y'A u16");
if (out_linear)
file_format = babl_format ("YA u16");
else
file_format = babl_format ("Y'A u16");
bit_depth = 16;
break;
case PNG_FORMAT_AUTO:
g_return_val_if_reached (FALSE);
}
}
@ -1868,9 +1914,8 @@ save_image (const gchar *filename,
g_free (profile_name);
*profile_saved = TRUE;
g_object_unref (profile);
}
if (profile)
g_object_unref (profile);
#endif
#ifdef PNG_zTXt_SUPPORTED