[libpng15] Fix PNG_SIMPLIFIED transformations,
adding alpha and reducing to 8-bit
diff --git a/pngread.c b/pngread.c
index c4fb05b..f6ab7e5 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1708,12 +1708,13 @@
{
png_uint_32 base_format = png_image_format(png_ptr, info_ptr);
png_uint_32 change = format ^ base_format;
+ png_fixed_point output_gamma;
+ int mode; /* alpha mode */
/* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
*/
{
- png_fixed_point input_gamma_default, output_gamma;
- int mode;
+ png_fixed_point input_gamma_default;
if (base_format & PNG_FORMAT_FLAG_LINEAR)
input_gamma_default = PNG_GAMMA_LINEAR;
@@ -1722,7 +1723,7 @@
if (linear)
{
- mode = PNG_ALPHA_STANDARD;
+ mode = PNG_ALPHA_STANDARD; /* associated alpha */
output_gamma = PNG_GAMMA_LINEAR;
}
@@ -1732,24 +1733,25 @@
output_gamma = PNG_DEFAULT_sRGB;
}
- /* Set the mode, the default gamma for the file and then, if it
- * doesn't match the default, the output gamma.
+ /* If the input default and output gamma do not match, because sRGB is
+ * being changed to linear, set the input default now via a dummy call
+ * to png_set_alpha_mode_fixed.
*/
- png_set_alpha_mode_fixed(png_ptr, mode, input_gamma_default);
if (input_gamma_default != output_gamma)
- png_set_alpha_mode(png_ptr, mode, output_gamma);
+ png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG,
+ input_gamma_default);
+ }
- /* If the bit-depth changes then handle that here. */
- if (change & PNG_FORMAT_FLAG_LINEAR)
- {
- if (linear /*16-bit output*/)
- png_set_expand_16(png_ptr);
+ /* If the bit-depth changes then handle that here. */
+ if (change & PNG_FORMAT_FLAG_LINEAR)
+ {
+ if (linear /*16-bit output*/)
+ png_set_expand_16(png_ptr);
- else /* 8-bit output */
- png_set_scale_16(png_ptr);
+ else /* 8-bit output */
+ png_set_scale_16(png_ptr);
- change &= ~PNG_FORMAT_FLAG_LINEAR;
- }
+ change &= ~PNG_FORMAT_FLAG_LINEAR;
}
/* Now the background/alpha channel changes. */
@@ -1761,9 +1763,11 @@
*/
if (base_format & PNG_FORMAT_FLAG_ALPHA)
{
+ /* 16-bit output: just remove the channel */
if (linear) /* compose on black (well, pre-multiply) */
png_set_strip_alpha(png_ptr);
+ /* 8-bit output: do an appropriate compose */
else if (display->background != NULL)
{
png_color_16 c;
@@ -1793,8 +1797,7 @@
* one so the code only has to hack on the pixels that require
* composition.
*/
- png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED,
- PNG_DEFAULT_sRGB);
+ mode = PNG_ALPHA_OPTIMIZED;
}
}
@@ -1804,12 +1807,26 @@
* been accomplished, so always add the alpha channel after the
* component channels.
*/
- png_set_add_alpha(png_ptr, 255/*opaque*/, PNG_FILLER_AFTER);
+ png_uint_32 filler; /* opaque filler */
+
+ if (linear)
+ filler = 65535;
+
+ else
+ filler = 255;
+
+ png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
}
change &= ~PNG_FORMAT_FLAG_ALPHA;
}
+ /* Now set the alpha mode correctly; this is always done, even if there is
+ * no alpha channel in either the input or the output because it correctly
+ * sets the output gamma.
+ */
+ png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
+
if (change & PNG_FORMAT_FLAG_COLOR)
{
/* gray<->color transformation required. */
diff --git a/pngwrite.c b/pngwrite.c
index 9c2e533..8050fba 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1910,6 +1910,9 @@
++in_ptr;
++out_ptr;
} /* while out_ptr < row_end */
+
+ png_write_row(png_ptr, output_row);
+ input_row += display->row_bytes/(sizeof (png_uint_16));
} /* while y */
}
