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Alpha channel should be 1 by default, rather than 0 #2197

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Alpha channel should be 1 by default, rather than 0 #2197

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4 changes: 2 additions & 2 deletions src/OpenColorIO/ImagePacking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ void Generic<Type>::PackRGBAFromImageDesc(const GenericImageDesc & srcImg,
inBitDepthBuffer[4*pixelsCopied+0] = *rPtr;
inBitDepthBuffer[4*pixelsCopied+1] = *gPtr;
inBitDepthBuffer[4*pixelsCopied+2] = *bPtr;
inBitDepthBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : (Type)0.0f;
inBitDepthBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : (Type)1.0f;
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Thanks for your contribution.

The idea is if the input image doesn't have an alpha channel, we need to consider the pixels as fully opaque instead of fully transparent (alpha=0). For floating point types fully opaque is represented as 1.0f but for integer types it needs to be the max value the type can hold (e.g. for 8-bit types it's 255)

Please check BithDepthUtils.h, the templated struct BitDepthInfo will be useful.

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Ahh, I got you, thanks @cozdas! Let me take a look at that file and fix it, will comment if any questions.


pixelsCopied++;
xIndex++;
Expand Down Expand Up @@ -140,7 +140,7 @@ void Generic<float>::PackRGBAFromImageDesc(const GenericImageDesc & srcImg,
outputBuffer[4*pixelsCopied+0] = *rPtr;
outputBuffer[4*pixelsCopied+1] = *gPtr;
outputBuffer[4*pixelsCopied+2] = *bPtr;
outputBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : 0.0f;
outputBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : 1.0f;

pixelsCopied++;
xIndex++;
Expand Down
46 changes: 23 additions & 23 deletions tests/cpu/CPUProcessor_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -276,9 +276,9 @@ OCIO_ADD_TEST(CPUProcessor, with_one_matrix)
1.0000f, 1.2500f, 1.9900f };

const std::vector<float> resImg
= { -0.01929f, -0.3995f, 0.4002f, 0.5f,
1.58960f, 0.9050f, 1.5025f, 0.5f,
2.070699f, 1.6505f, 2.4002f, 0.5f };
= { -0.01929f, -0.3995f, 0.4002f, 1.5f,
1.58960f, 0.9050f, 1.5025f, 1.5f,
2.070699f, 1.6505f, 2.4002f, 1.5f };

ComputeValues<OCIO::BIT_DEPTH_F32, OCIO::BIT_DEPTH_F32>(
__LINE__, processor,
Expand Down Expand Up @@ -620,10 +620,10 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
5120, 20480, 65535 };

const std::vector<uint16_t> resImg
= { 95, 24, 0, 0,
268, 178, 123, 0,
955, 598, 394, 0,
65535, 8589, 1986, 0 };
= { 95, 24, 0, 1,
268, 178, 123, 1,
955, 598, 394, 1,
65535, 8589, 1986, 1 };

ComputeValues<OCIO::BIT_DEPTH_UINT16, OCIO::BIT_DEPTH_UINT16>(
__LINE__, processor,
Expand Down Expand Up @@ -656,10 +656,10 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
128, 1023, 640 };

const std::vector<uint16_t> ui10_resImg
= { 0, 6, 15, 0,
26, 48, 106, 0,
36, 106, 252, 0,
48, 1023, 384, 0 };
= { 0, 6, 15, 1,
26, 48, 106, 1,
36, 106, 252, 1,
48, 1023, 384, 1 };

ComputeValues<OCIO::BIT_DEPTH_UINT10, OCIO::BIT_DEPTH_UINT10>(
__LINE__, processor,
Expand All @@ -668,10 +668,10 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
NB_PIXELS);

const std::vector<uint16_t> ui16_resImg
= { 0, 394, 955, 0,
1656, 3092, 6794, 0,
2301, 6794, 16162, 0,
3092, 65535, 24593, 0 };
= { 0, 394, 955, 64,
1656, 3092, 6794, 64,
2301, 6794, 16162, 64,
3092, 65535, 24593, 64 };

ComputeValues<OCIO::BIT_DEPTH_UINT10, OCIO::BIT_DEPTH_UINT16>(
__LINE__, processor,
Expand Down Expand Up @@ -704,21 +704,21 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
1024, 2048, 4095 };

const std::vector<uint16_t> ui12_resImg
= { 0, 11, 25, 0,
37, 60, 103, 0,
49, 103, 193, 0,
424, 1009, 4095, 0 };
= { 0, 11, 25, 1,
37, 60, 103, 1,
49, 103, 193, 1,
424, 1009, 4095, 1 };

ComputeValues<OCIO::BIT_DEPTH_UINT12, OCIO::BIT_DEPTH_UINT12>(
__LINE__, processor,
&ui12_inImg[0], OCIO::CHANNEL_ORDERING_RGB,
&ui12_resImg[0], OCIO::CHANNEL_ORDERING_RGBA,
NB_PIXELS);
const std::vector<uint16_t> ui16_resImg
= { 0, 178, 394, 0,
598, 955, 1655, 0,
779, 1655, 3089, 0,
6789, 16143, 65535, 0 };
= { 0, 178, 394, 16,
598, 955, 1655, 16,
779, 1655, 3089, 16,
6789, 16143, 65535, 16 };

ComputeValues<OCIO::BIT_DEPTH_UINT12, OCIO::BIT_DEPTH_UINT16>(
__LINE__, processor,
Expand Down