bmp specified BI_BITFIELDS should take care RGBA bit mask #20875
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use cv::imread(pcszFileName, cv::IMREAD_UNCHANGED) function to read the bmp file test_Icon.bmp(I added into "\opencv\modules\imgcodecs\test" folder), you will find the color is wrong, the bitmap data order in test_Icon.bmp is ABGR, but the BmpDecoder::readData method copy it as BGRA. |
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I modify the code |
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Thank you for contribution!
Please use lowercase letters in filenames. This file should go to opencv_extra repository (like any other testdata). Please add regression test for this case in modules/imgcodecs/test/. |
modules/imgcodecs/src/grfmt_bmp.cpp
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| if (!color) | ||
| icvCvt_BGRA2Gray_8u_C4C1R(src, 0, data, 0, Size(m_width, 1)); | ||
| else if (img.channels() == 3) |
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indentation in OpenCV is 4 spaces (no tabs)
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I've finished coding, please review, thanks! |
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I found that xrgb bmp file which export by GIMP is specified the BI_BITFIELDS, the alpha channel bit mask in this kind of file is 0, it is means no alpha channel, so need to set alpha as 255. |
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I have xrgb test file, do I need to pust it to opencv_extra repo and add one more test case? |
Sure! |
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| const Mat img = cv::imread(filenameInput, IMREAD_UNCHANGED); | ||
| ASSERT_FALSE(img.empty()); | ||
| ASSERT_EQ(CV_8UC4, img.type()); |
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Extra checks are necessary here.
These tests should FAIL without changes in modules/imgcodecs/src/grfmt_bmp.cpp
Tests should PASS with changes.
Otherwise we can lost or break code for these cases in the future.
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oh! the difference between those two cases is the alpha byte, I updated the test case.
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Thank you for update! Currently tests work as expected.
Please restore the .type() checks.
* bmp specified BI_BITFIELDS should take care RGBA bit mask * change the name * support xrgb bmp file * support xrgb bmp file(add test case) * update testing code
Merge with extra: opencv/opencv_extra#925
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Patch to opencv_extra has the same branch name.
How to test: use cv::imread(pcszFileName, cv::IMREAD_UNCHANGED) function to read the bmp file test_Icon.bmp(I added into "\opencv\modules\imgcodecs\test" folder), you will find the color is wrong, the bitmap data order in test_Icon.bmp is ABGR, but the BmpDecoder::readData method copy as BGRA.