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Handle non-integer and out-of-range values correctly in Indexed color spaces

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In PDF version 2.0 the handling of Indexed color spaces was clarified as follows:
> The index value should be an integer in the range 0 to hival. If the value is a real number, it shall be rounded to the nearest integer (0.5 values shall be rounded up); if it is outside the range 0 to hival, it shall be adjusted to the nearest value within that range.

Please refer to https://github.com/pdf-association/pdf-differences/tree/main/IndexedColor
This commit is contained in:
Jonas Jenwald 2025-04-09 15:24:09 +02:00
parent 22657e2b6e
commit fbc4f4b12a
4 changed files with 105 additions and 7 deletions
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16
src/core/colorspace.js
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@ -429,6 +429,7 @@ class IndexedCS extends ColorSpace {
constructor(base, highVal, lookup) {
super("Indexed", 1);
this.base = base;
this.highVal = highVal;
const length = base.numComps * (highVal + 1);
this.lookup = new Uint8Array(length);
@ -452,9 +453,10 @@ class IndexedCS extends ColorSpace {
'IndexedCS.getRgbItem: Unsupported "dest" type.'
);
}
const numComps = this.base.numComps;
const start = src[srcOffset] * numComps;
this.base.getRgbBuffer(this.lookup, start, 1, dest, destOffset, 8, 0);
const { base, highVal, lookup } = this;
const start =
MathClamp(Math.round(src[srcOffset]), 0, highVal) * base.numComps;
base.getRgbBuffer(lookup, start, 1, dest, destOffset, 8, 0);
}
getRgbBuffer(src, srcOffset, count, dest, destOffset, bits, alpha01) {
@ -464,13 +466,13 @@ class IndexedCS extends ColorSpace {
'IndexedCS.getRgbBuffer: Unsupported "dest" type.'
);
}
const base = this.base;
const numComps = base.numComps;
const { base, highVal, lookup } = this;
const { numComps } = base;
const outputDelta = base.getOutputLength(numComps, alpha01);
const lookup = this.lookup;
for (let i = 0; i < count; ++i) {
const lookupPos = src[srcOffset++] * numComps;
const lookupPos =
MathClamp(Math.round(src[srcOffset++]), 0, highVal) * numComps;
base.getRgbBuffer(lookup, lookupPos, 1, dest, destOffset, 8, alpha01);
destOffset += outputDelta;
}