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LibGfx/ICC: In lerp_nd(), use VLAs for left_index, factor

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`x.size()` is 3 or 4 in practice and at most 15 in theory
(cf `number_of_components_in_color_space()` in Profile.cpp),
so using a VLA for these should be fine from a stack size PoV.

They're accessed from two local loops iterating from 0 to
`x.size()`, so it's hopefully not too risky from a security
PoV either.

Takes

    Build/lagom/bin/image --no-output \
        --assign-color-profile \
            Build/lagom/Root/res/icc/Adobe/CMYK/USWebCoatedSWOP.icc \
        --convert-to-color-profile serenity-sRGB.icc \
        cmyk.jpg

from 2.81s to 2.74s on my machine, about 2.5% faster.
This commit is contained in:
Nico Weber 2024-02-02 21:48:31 -05:00 • committed by Andreas Kling
parent 69df94ec5c
commit a352099b05
1 changed files with 4 additions and 4 deletions
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8
Userland/Libraries/LibGfx/ICC/TagTypes.h
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@ -37,13 +37,13 @@ float lerp_1d(ReadonlySpan<T> values, float x)
// `sample()` gets a vector where 0 <= i'th coordinate < size(i) and should return the value of the look-up table at that position.
inline FloatVector3 lerp_nd(Function<unsigned(size_t)> size, Function<FloatVector3(Vector<unsigned> const&)> sample, Vector<float> const& x)
{
Vector<unsigned, 4> left_index;
Vector<float, 4> factor;
unsigned left_index[x.size()];
float factor[x.size()];
for (size_t i = 0; i < x.size(); ++i) {
unsigned n = size(i) - 1;
float ec = x[i] * n;
left_index.append(min(static_cast<unsigned>(ec), n - 1));
factor.append(ec - left_index[i]);
left_index[i] = min(static_cast<unsigned>(ec), n - 1);
factor[i] = ec - left_index[i];
}
FloatVector3 sample_output {};