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[PATCH v7.2.3 20/30] ui: Fix pixel colour channel order for PNG screensh
From: |
Michael Tokarev |
Subject: |
[PATCH v7.2.3 20/30] ui: Fix pixel colour channel order for PNG screenshots |
Date: |
Wed, 17 May 2023 12:10:32 +0300 |
From: Peter Maydell <peter.maydell@linaro.org>
When we take a PNG screenshot the ordering of the colour channels in
the data is not correct, resulting in the image having weird
colouring compared to the actual display. (Specifically, on a
little-endian host the blue and red channels are swapped; on
big-endian everything is wrong.)
This happens because the pixman idea of the pixel data and the libpng
idea differ. PIXMAN_a8r8g8b8 defines that pixels are 32-bit values,
with A in bits 24-31, R in bits 16-23, G in bits 8-15 and B in bits
0-7. This means that on little-endian systems the bytes in memory
are
B G R A
and on big-endian systems they are
A R G B
libpng, on the other hand, thinks of pixels as being a series of
values for each channel, so its format PNG_COLOR_TYPE_RGB_ALPHA
always wants bytes in the order
R G B A
This isn't the same as the pixman order for either big or little
endian hosts.
The alpha channel is also unnecessary bulk in the output PNG file,
because there is no alpha information in a screenshot.
To handle the endianness issue, we already define in ui/qemu-pixman.h
various PIXMAN_BE_* and PIXMAN_LE_* values that give consistent
byte-order pixel channel formats. So we can use PIXMAN_BE_r8g8b8 and
PNG_COLOR_TYPE_RGB, which both have an in-memory byte order of
R G B
and 3 bytes per pixel.
(PPM format screenshots get this right; they already use the
PIXMAN_BE_r8g8b8 format.)
Cc: qemu-stable@nongnu.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1622
Fixes: 9a0a119a382867 ("Added parameter to take screenshot with screendump as
PNG")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20230502135548.2451309-1-peter.maydell@linaro.org
(cherry picked from commit cd22a0f520f471e3bd33bc19cf3b2fa772cdb2a8)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
ui/console.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/ui/console.c b/ui/console.c
index 3c0d9b061a..646202214a 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -307,7 +307,7 @@ static bool png_save(int fd, pixman_image_t *image, Error
**errp)
png_struct *png_ptr;
png_info *info_ptr;
g_autoptr(pixman_image_t) linebuf =
- qemu_pixman_linebuf_create(PIXMAN_a8r8g8b8, width);
+ qemu_pixman_linebuf_create(PIXMAN_BE_r8g8b8, width);
uint8_t *buf = (uint8_t *)pixman_image_get_data(linebuf);
FILE *f = fdopen(fd, "wb");
int y;
@@ -337,7 +337,7 @@ static bool png_save(int fd, pixman_image_t *image, Error
**errp)
png_init_io(png_ptr, f);
png_set_IHDR(png_ptr, info_ptr, width, height, 8,
- PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
+ PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
png_write_info(png_ptr, info_ptr);
--
2.39.2
- [PATCH v7.2.3 09/30] hw/arm/aspeed: Use arm_write_bootloader() to write the bootloader, (continued)
- [PATCH v7.2.3 09/30] hw/arm/aspeed: Use arm_write_bootloader() to write the bootloader, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 11/30] hw/intc/allwinner-a10-pic: Don't use set_bit()/clear_bit(), Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 12/30] target/arm: Define and use new load_cpu_field_low32(), Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 13/30] hw/sd/allwinner-sdhost: Correctly byteswap descriptor fields, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 14/30] hw/net/allwinner-sun8i-emac: Correctly byteswap descriptor fields, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 19/30] accel/tcg: Fix atomic_mmu_lookup for reads, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 17/30] block: Fix use after free in blockdev_mark_auto_del(), Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 16/30] meson: leave unnecessary modules out of the build, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 18/30] target/riscv: Fix itrigger when icount is used, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 22/30] tcg: ppc64: Fix mask generation for vextractdm, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 20/30] ui: Fix pixel colour channel order for PNG screenshots,
Michael Tokarev <=
- [PATCH v7.2.3 24/30] virtio: fix reachable assertion due to stale value of cached region size, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 15/30] softfloat: Fix the incorrect computation in float32_exp2, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 21/30] async: Suppress GCC13 false positive in aio_bh_poll(), Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 23/30] hw/virtio/vhost-user: avoid using unitialized errp, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 26/30] target/s390x: Fix EXECUTE of relative branches, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 25/30] block/monitor: Fix crash when executing HMP commit, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 29/30] Revert "vhost-user: Monitor slave channel in vhost_user_read()", Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 27/30] 9pfs/xen: Fix segfault on shutdown, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 28/30] xen/pt: reserve PCI slot 2 for Intel igd-passthru, Michael Tokarev, 2023/05/17
- [PATCH v7.2.3 30/30] Revert "vhost-user: Introduce nested event loop in vhost_user_read()", Michael Tokarev, 2023/05/17