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LibGfx/ICC: Extract a lerp_1d() function

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Pure code move, no behavior change.
This commit is contained in:
Nico Weber 2023-12-04 08:01:50 -05:00 • committed by Andreas Kling
parent 4c4daf4a62
commit 9372f6d726
1 changed files with 16 additions and 6 deletions
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22
Userland/Libraries/LibGfx/ICC/TagTypes.h
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@ -20,6 +20,21 @@
namespace Gfx::ICC { namespace Gfx::ICC {
// Does one-dimensional linear interpolation over a lookup table.
// Takes a span of values an x in [0.0, 1.0].
// Finds the two values in the span closest to x (where x = 0.0 is the span's first element and x = 1.0 the span's last element),
// and linearly interpolates between those two values, assumes all values are the same amount apart.
template<class T>
float lerp_1d(ReadonlySpan<T> values, float x)
{
size_t n = values.size() - 1;
size_t i = static_cast<size_t>(x * n);
if (i == values.size() - 1)
--i;
return mix(static_cast<float>(values[i]), static_cast<float>(values[i + 1]), x * n - i);
}
// Does multi-dimensional linear interpolation over a lookup table. // Does multi-dimensional linear interpolation over a lookup table.
// `size(i)` should returns the number of samples in the i'th dimension. // `size(i)` should returns the number of samples in the i'th dimension.
// `sample()` gets a vector where 0 <= i'th coordinate < size(i) and should return the value of the look-up table at that position. // `sample()` gets a vector where 0 <= i'th coordinate < size(i) and should return the value of the look-up table at that position.
@ -207,12 +222,7 @@ public:
if (values().size() == 1) if (values().size() == 1)
return powf(x, values()[0] / (float)0x100); return powf(x, values()[0] / (float)0x100);
size_t n = values().size() - 1; return lerp_1d(values().span(), x) / 65535.0f;
size_t i = static_cast<size_t>(x * n);
if (i == values().size() - 1)
--i;
return mix(values()[i] / 65535.f, values()[i + 1] / 65535.f, x * n - i);
} }
// y must be in [0..1]. // y must be in [0..1].