colorconversion: add support for promoting < 8 bit planar to 8 bit planar #1080
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farindk
reviewed
Dec 26, 2023
| for (int y = 0; y < height; y++) | ||
| for (int x = 0; x < width; x++) { | ||
| int in = p_in[y * stride_in + x]; | ||
| p_out[y * stride_out + x] = (uint8_t) (in << shift); // TODO: I think no rounding here, but am not sure. |
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The usual technique is to use (in << shift) | (in >> (2*input_bits - 8). This puts the MSBs into the LSBs that were shifted in. The advantage is that full white (e.g. 0x3F in 6 bit) also gets mapped to (0xFF in 8 bits) instead of some grey.
farindk
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Dec 26, 2023
farindk
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Dec 26, 2023
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I have changed the convertion such that also inputs with <4 bits can be converted with the full output value range. |
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This is a partial fix for color conversion from planar RGB with bit depth less than 8 bit into 8 bit. It extends an existing operation (
Op_to_sdr_planes) to handle this case.This is enough to get my uncompressed codec rework with
heif-convertto generate JPEG. However it is not sufficient for PNG.