inverseResponseQ16()

i32 fl::anonymous_namespace{pipeline.cpp.hpp}::inverseResponseQ16	(	i32	light,
		const vector< u16 > &	values )

Invert piecewise-linear code-to-light data.

The first sample that reaches the requested light wins at a plateau; zero and full-scale are exact.

Definition at line 31 of file pipeline.cpp.hpp.

                                                                          {
    if (light <= 0) return 0;
    if (light >= 65536) return 65536;
    const u32 target =
        (static_cast<u32>(light) * 65535u + 32768u) >> 16;
    u32 low = 1;
    u32 high = static_cast<u32>(values.size() - 1);
    while (low < high) {
        const u32 middle = low + (high - low) / 2;
        if (values[middle] >= target) high = middle;
        else low = middle + 1;
    }
    high = low;
    const u32 low_value = values[high - 1];
    const u32 high_value = values[high];
    // A plateau at the requested light maps to its first attainable code.
    if (high_value == low_value) {
        return static_cast<i32>((high - 1) * 65536u /
                                static_cast<u32>(values.size() - 1));
    }
    const u32 interval = high_value - low_value;
    const u32 fraction =
        ((target - low_value) * 65536u + interval / 2) / interval;
    const u32 segments = static_cast<u32>(values.size() - 1);
    return static_cast<i32>(((high - 1) * 65536u + fraction + segments / 2) /
                            segments);
}

References fl::FL_NO_EXCEPT, and inverseResponseQ16().

Referenced by inverseResponseQ16().

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