Function postprocessLab

src/imageio/TiffImageLoader.cpp:1435–1545

}

Task<void> postprocessLab(
    TIFF* tif,
    const uint16_t photometric,
    const uint16_t dataBitsPerSample,
    const size_t numColorChannels,
    const MultiChannelView<float>& rgbaView,
    ImageData& resultData,
    const int priority
) {
    if (numColorChannels != 3) {
        throw ImageLoadError{"CIELAB images without 3 color channels are not supported."};
    }

    const Vector2i size = resultData.size();
    const size_t numPixels = posProd(size);

    // Step 1: Decode the encoded values to CIE L*a*b* [L: 0..100, a: -128..127, b: -128..127]
    if (photometric == PHOTOMETRIC_CIELAB) {
        co_await ThreadPool::global().parallelFor(
            0uz,
            numPixels,
            numPixels * numColorChannels,
            [&](size_t i) {
                rgbaView[0, i] *= 100.0f;
                for (size_t c = 1; c < numColorChannels; ++c) {
                    float& v = rgbaView[c, i];
                    v *= 255.0f;
                    v = v >= 128.0f ? v - 256.0f : v;
                }
            },
            priority
        );
    } else if (photometric == PHOTOMETRIC_ICCLAB) {
        co_await ThreadPool::global().parallelFor(
            0uz,
            numPixels,
            numPixels * numColorChannels,
            [&](size_t i) {
                rgbaView[0, i] *= 100.0f;
                for (size_t c = 1; c < numColorChannels; ++c) {
                    float& v = rgbaView[c, i];
                    v = v * 255.0f - 128.0f;
                }
            },
            priority
        );
    } else if (photometric == PHOTOMETRIC_ITULAB) {
        Vector3f decodeMin = {0.0f, -85.0f, -85.0f}, decodeMax = {100.0f, 85.0f, 85.0f};
        if (const auto decode = tiffGetSpan<float>(tif, TIFFTAG_DECODE); decode.size() >= 6) {
            decodeMin = {decode[0], decode[2], decode[4]};
            decodeMax = {decode[1], decode[3], decode[5]};

            tlog::debug("Found ITULAB Decode tag: min={} max={}", decodeMin, decodeMax);
        }

        co_await ThreadPool::global().parallelFor(
            0uz,
            numPixels,