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Merge pull request #26835 from sturkmen72:patch-4

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Corrections on bKGD chunk writing and reading in PNG #26835 

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
This commit is contained in:
Suleyman TURKMEN 2025-01-25 09:31:00 +03:00 committed by GitHub
parent a2dd4ddbb2
commit d4eed1c5aa
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GPG Key ID: B5690EEEBB952194
2 changed files with 46 additions and 15 deletions
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26
modules/imgcodecs/src/grfmt_png.cpp
View File

@ -327,11 +327,10 @@ bool PngDecoder::readHeader()
if (id == id_bKGD)
{
// The spec is actually more complex: http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.bKGD
int bgcolor = png_get_uint_32(&chunk.p[8]);
m_animation.bgcolor[3] = (bgcolor >> 24) & 0xFF;
m_animation.bgcolor[2] = (bgcolor >> 16) & 0xFF;
m_animation.bgcolor[1] = (bgcolor >> 8) & 0xFF;
m_animation.bgcolor[0] = bgcolor & 0xFF;
m_animation.bgcolor[0] = png_get_uint_16(&chunk.p[8]);
m_animation.bgcolor[1] = png_get_uint_16(&chunk.p[10]);
m_animation.bgcolor[2] = png_get_uint_16(&chunk.p[12]);
m_animation.bgcolor[3] = 0;
}
if (id == id_PLTE || id == id_tRNS)
@ -721,11 +720,10 @@ uint32_t PngDecoder::read_chunk(Chunk& chunk)
if (size != 8 + 26 + 4)
return 0;
} else if (id == id_bKGD) {
// 8=HDR+size, ??=size of bKGD chunk, 4=CRC
// 8=HDR+size, (1, 2 or 6)=size of bKGD chunk, 4=CRC
// The spec is actually more complex:
// http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.bKGD
// TODO: we only check that 4 bytes can be read from &chunk.p[8]. Fix.
if (size < 8 + 4)
if (size != 8 + 1 + 4 && size != 8 + 2 + 4 && size != 8 + 6 + 4)
return 0;
} else if (id != id_fdAT && id != id_IDAT && id != id_IEND && id != id_PLTE && id != id_tRNS) {
if (size > PNG_USER_CHUNK_MALLOC_MAX)
@ -1533,13 +1531,13 @@ bool PngEncoder::writeanimation(const Animation& animation, const std::vector<in
if (palsize > 0)
writeChunk(m_f, "PLTE", (unsigned char*)(&palette), palsize * 3);
if ((animation.bgcolor != Scalar()) && (animation.frames.size() > 1))
if ((animation.bgcolor != Scalar()) && coltype)
{
uint64_t bgvalue = (static_cast<int>(animation.bgcolor[0]) & 0xFF) << 24 |
(static_cast<int>(animation.bgcolor[1]) & 0xFF) << 16 |
(static_cast<int>(animation.bgcolor[2]) & 0xFF) << 8 |
(static_cast<int>(animation.bgcolor[3]) & 0xFF);
writeChunk(m_f, "bKGD", (unsigned char*)(&bgvalue), 6); //the bKGD chunk must precede the first IDAT chunk, and must follow the PLTE chunk.
unsigned char bgvalue[6] = {};
bgvalue[1] = animation.bgcolor[0];
bgvalue[3] = animation.bgcolor[1];
bgvalue[5] = animation.bgcolor[2];
writeChunk(m_f, "bKGD", bgvalue, 6); //the bKGD chunk must precede the first IDAT chunk, and must follow the PLTE chunk.
}
if (trnssize > 0)

35
modules/imgcodecs/test/test_animation.cpp
View File

@ -425,6 +425,39 @@ TEST(Imgcodecs_APNG, imwriteanimation_rgb)
EXPECT_EQ(0, remove(output.c_str()));
}
TEST(Imgcodecs_APNG, imwriteanimation_gray)
{
Animation s_animation, l_animation;
EXPECT_TRUE(fillFrames(s_animation, false));
for (size_t i = 0; i < s_animation.frames.size(); i++)
{
cvtColor(s_animation.frames[i], s_animation.frames[i], COLOR_BGR2GRAY);
}
s_animation.bgcolor = Scalar(50, 100, 150);
string output = cv::tempfile(".png");
// Write the animation to a .png file and verify success.
EXPECT_TRUE(imwriteanimation(output, s_animation));
// Read the animation back and compare with the original.
EXPECT_TRUE(imreadanimation(output, l_animation));
EXPECT_EQ(Scalar(), l_animation.bgcolor);
size_t expected_frame_count = s_animation.frames.size() - 2;
// Verify that the number of frames matches the expected count.
EXPECT_EQ(expected_frame_count, imcount(output));
EXPECT_EQ(expected_frame_count, l_animation.frames.size());
EXPECT_EQ(0, remove(output.c_str()));
for (size_t i = 0; i < l_animation.frames.size(); i++)
{
EXPECT_EQ(0, cvtest::norm(s_animation.frames[i], l_animation.frames[i], NORM_INF));
}
}
TEST(Imgcodecs_APNG, imwritemulti_rgba)
{
Animation s_animation;
@ -492,7 +525,7 @@ TEST(Imgcodecs_APNG, imwriteanimation_bgcolor)
{
Animation s_animation, l_animation;
EXPECT_TRUE(fillFrames(s_animation, true, 2));
s_animation.bgcolor = Scalar(50, 100, 150, 128); // different values for test purpose.
s_animation.bgcolor = Scalar(50, 100, 150); // will be written in bKGD chunk as RGB.
// Create a temporary output filename for saving the animation.
string output = cv::tempfile(".png");