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Convert the /Indexed palette in a single base color space call

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`IndexedCS` invoked the base color space once per palette entry, which is
cheap for e.g. `DeviceRgbCS` but not for `IccColorSpace` where every call
is a Wasm round-trip.
This commit is contained in:
calixteman 2026-07-25 21:06:26 +02:00
parent f38ea2d4cc
commit a0f100c4a8
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GPG Key ID: 0C5442631EE0691F
1 changed files with 33 additions and 18 deletions
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51
src/core/colorspace.js
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@ -446,24 +446,36 @@ class PatternCS extends ColorSpace {
* The default color is `new Uint8Array([0])`.
*/
class IndexedCS extends ColorSpace {
#rgbLookup;
constructor(base, highVal, lookup) {
super("Indexed", 1);
this.base = base;
this.highVal = highVal;
const length = base.numComps * (highVal + 1);
this.lookup = new Uint8Array(length);
const count = highVal + 1;
const length = base.numComps * count;
const palette = new Uint8Array(length);
if (lookup instanceof BaseStream) {
const bytes = lookup.getBytes(length);
this.lookup.set(bytes);
palette.set(lookup.getBytes(length));
} else if (typeof lookup === "string") {
for (let i = 0; i < length; ++i) {
this.lookup[i] = lookup.charCodeAt(i) & 0xff;
palette[i] = lookup.charCodeAt(i);
}
} else {
throw new FormatError(`IndexedCS - unrecognized lookup table: ${lookup}`);
}
this.#rgbLookup = new Uint8ClampedArray(count * 3);
base.getRgbBuffer(
palette,
0,
count,
this.#rgbLookup,
0,
/* bits = */ 8,
/* alpha01 = */ 0
);
}
getRgbItem(src, srcOffset, dest, destOffset) {
@ -473,10 +485,12 @@ class IndexedCS extends ColorSpace {
'IndexedCS.getRgbItem: Unsupported "dest" type.'
);
}
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);
const rgbLookup = this.#rgbLookup;
const pos = MathClamp(Math.round(src[srcOffset]), 0, this.highVal) * 3;
dest[destOffset] = rgbLookup[pos];
dest[destOffset + 1] = rgbLookup[pos + 1];
dest[destOffset + 2] = rgbLookup[pos + 2];
}
getRgbBuffer(src, srcOffset, count, dest, destOffset, bits, alpha01) {
@ -486,20 +500,21 @@ class IndexedCS extends ColorSpace {
'IndexedCS.getRgbBuffer: Unsupported "dest" type.'
);
}
const { base, highVal, lookup } = this;
const { numComps } = base;
const outputDelta = base.getOutputLength(numComps, alpha01);
const { highVal } = this;
const rgbLookup = this.#rgbLookup;
for (let i = 0; i < count; ++i) {
const lookupPos =
MathClamp(Math.round(src[srcOffset++]), 0, highVal) * numComps;
base.getRgbBuffer(lookup, lookupPos, 1, dest, destOffset, 8, alpha01);
destOffset += outputDelta;
const pos = MathClamp(Math.round(src[srcOffset++]), 0, highVal) * 3;
dest[destOffset++] = rgbLookup[pos];
dest[destOffset++] = rgbLookup[pos + 1];
dest[destOffset++] = rgbLookup[pos + 2];
destOffset += alpha01;
}
}
getOutputLength(inputLength, alpha01) {
return this.base.getOutputLength(inputLength * this.base.numComps, alpha01);
return inputLength * (3 + alpha01);
}
isDefaultDecode(decode, bpc) {