From: Paul Eggert <eggert@cs.ucla.edu>
To: YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>,
Roland Winkler <winkler@gnu.org>
Cc: 37153@debbugs.gnu.org
Subject: bug#37153: 26.1; some png images scrambled
Date: Sun, 25 Aug 2019 11:38:07 -0700 [thread overview]
Message-ID: <4a893dc7-659a-be76-01d3-3f0a4de57ba4@cs.ucla.edu> (raw)
In-Reply-To: <wlwof1ive4.wl-mituharu@math.s.chiba-u.ac.jp>
[-- Attachment #1: Type: text/plain, Size: 627 bytes --]
YAMAMOTO Mitsuharu wrote:
> It seems to be necessary to look into the tRNS chunk data for paletted
> images. Again, W32 would need some more work.
Thanks, I confirmed that this fixes the misdisplay for me as well. I attempted
to port it to w32 (as well as to unusual libpng builds that do not define
PNG_tRNS_SUPPORTED) and installed the attached into master.
With this patch on Ubuntu 18.04.3 I always see the first image shown in your
tRNS.pg screenshot <https://bugs.gnu.org/37153#56>. So it may be that more work
needs to be done to support other faces. Still, this patch is an improvement so
it's worth going in.
[-- Attachment #2: 0001-Fix-misdisplay-of-PNG-paletted-images.patch --]
[-- Type: text/x-patch, Size: 3729 bytes --]
From 64aa756cfa5943c8b3494ac1fbb4db712c50ae64 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sun, 25 Aug 2019 10:01:46 -0700
Subject: [PATCH] Fix misdisplay of PNG paletted images
Problem reported by Roland Winkler (Bug#37153).
Derived from a patch suggested by YAMAMOTO Mitsuharu (Bug#37153#62).
* src/image.c (png_get_valid) [WINDOWSNT]:
Do not dynamically link this function.
(png_get_tRNS) [WINDOWSNT && PNG_tRNS_SUPPORTED]:
Dynamically link this function instead.
(png_load_body): Do not assume that every paletted image supplies
only transparency data. Fix typo in use of transparent_p.
---
src/image.c | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/src/image.c b/src/image.c
index 81d8cb4e2b..18495612e9 100644
--- a/src/image.c
+++ b/src/image.c
@@ -6234,7 +6234,10 @@ DEF_DLL_FN (void, png_read_info, (png_structp, png_infop));
DEF_DLL_FN (png_uint_32, png_get_IHDR,
(png_structp, png_infop, png_uint_32 *, png_uint_32 *,
int *, int *, int *, int *, int *));
-DEF_DLL_FN (png_uint_32, png_get_valid, (png_structp, png_infop, png_uint_32));
+# ifdef PNG_tRNS_SUPPORTED
+DEF_DLL_FN (png_uint_32, png_get_tRNS, (png_structp, png_infop, png_bytep *,
+ int *, png_color_16p *));
+# endif
DEF_DLL_FN (void, png_set_strip_16, (png_structp));
DEF_DLL_FN (void, png_set_expand, (png_structp));
DEF_DLL_FN (void, png_set_gray_to_rgb, (png_structp));
@@ -6273,7 +6276,9 @@ init_png_functions (void)
LOAD_DLL_FN (library, png_set_sig_bytes);
LOAD_DLL_FN (library, png_read_info);
LOAD_DLL_FN (library, png_get_IHDR);
- LOAD_DLL_FN (library, png_get_valid);
+# ifdef PNG_tRNS_SUPPORTED
+ LOAD_DLL_FN (library, png_get_tRNS);
+# endif
LOAD_DLL_FN (library, png_set_strip_16);
LOAD_DLL_FN (library, png_set_expand);
LOAD_DLL_FN (library, png_set_gray_to_rgb);
@@ -6304,7 +6309,7 @@ init_png_functions (void)
# undef png_get_IHDR
# undef png_get_io_ptr
# undef png_get_rowbytes
-# undef png_get_valid
+# undef png_get_tRNS
# undef png_longjmp
# undef png_read_end
# undef png_read_image
@@ -6329,7 +6334,7 @@ init_png_functions (void)
# define png_get_IHDR fn_png_get_IHDR
# define png_get_io_ptr fn_png_get_io_ptr
# define png_get_rowbytes fn_png_get_rowbytes
-# define png_get_valid fn_png_get_valid
+# define png_get_tRNS fn_png_get_tRNS
# define png_longjmp fn_png_longjmp
# define png_read_end fn_png_read_end
# define png_read_image fn_png_read_image
@@ -6589,10 +6594,21 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
/* If image contains simply transparency data, we prefer to
construct a clipping mask. */
- if (png_get_valid (png_ptr, info_ptr, PNG_INFO_tRNS))
- transparent_p = 1;
- else
- transparent_p = 0;
+ transparent_p = false;
+# ifdef PNG_tRNS_SUPPORTED
+ png_bytep trans_alpha;
+ int num_trans;
+ if (png_get_tRNS (png_ptr, info_ptr, &trans_alpha, &num_trans, NULL)
+ && trans_alpha)
+ {
+ int i;
+ for (i = 0; i < num_trans; i++)
+ if (0 < trans_alpha[i] && trans_alpha[i] < 255)
+ break;
+ if (! (i < num_trans))
+ transparent_p = true;
+ }
+# endif
/* This function is easier to write if we only have to handle
one data format: RGB or RGBA with 8 bits per channel. Let's
@@ -6680,7 +6696,7 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
/* Create an image and pixmap serving as mask if the PNG image
contains an alpha channel. */
if (channels == 4
- && !transparent_p
+ && transparent_p
&& !image_create_x_image_and_pixmap (f, img, width, height, 1,
&mask_img, 1))
{
--
2.17.1
next prev parent reply other threads:[~2019-08-25 18:38 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-23 4:49 bug#37153: 26.1; some png images scrambled Roland Winkler
2019-08-23 8:47 ` Eli Zaretskii
2019-08-23 11:39 ` Roland Winkler
2019-08-23 12:22 ` Eli Zaretskii
2019-08-23 15:07 ` Roland Winkler
2019-08-23 15:34 ` Eli Zaretskii
2019-08-23 19:37 ` Paul Eggert
2019-08-23 20:11 ` Eli Zaretskii
2019-08-23 20:33 ` Paul Eggert
2019-08-24 5:51 ` Eli Zaretskii
2019-08-24 3:17 ` Roland Winkler
2019-08-24 3:39 ` Paul Eggert
2019-08-24 4:19 ` Roland Winkler
2019-08-24 6:26 ` Eli Zaretskii
2019-08-24 6:22 ` Eli Zaretskii
2019-08-24 9:01 ` mituharu
2019-08-24 10:17 ` Eli Zaretskii
2019-08-25 4:19 ` YAMAMOTO Mitsuharu
2019-08-25 7:24 ` Eli Zaretskii
2019-08-25 4:52 ` Roland Winkler
2019-08-25 6:58 ` YAMAMOTO Mitsuharu
2019-08-25 12:19 ` Roland Winkler
2019-08-25 18:38 ` Paul Eggert [this message]
2019-08-25 18:56 ` Eli Zaretskii
2019-08-25 23:02 ` YAMAMOTO Mitsuharu
2019-08-25 23:06 ` YAMAMOTO Mitsuharu
2019-08-25 23:39 ` Paul Eggert
2019-09-24 16:23 ` Lars Ingebrigtsen
2019-09-24 17:14 ` Eli Zaretskii
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