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Improve caching of shading patterns. (bug 1721949)

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The PDF in bug 1721949 uses many unique pattern objects
that references the same shading many times. This caused
a new canvas pattern to be created and cached many times
driving up memory use.

To fix, I've changed the cache in the worker to key off the
shading object and instead send the shading and matrix
separately. While that worked well to fix the above bug,
there could be PDFs that use many shading that could
cause memory issues, so I've also added a LRU cache
on the main thread for canvas patterns. This should prevent
memory use from getting too high.
This commit is contained in:
Brendan Dahl 2021-07-27 19:58:06 -07:00
parent 777d890268
commit c836e1f0fb
4 changed files with 85 additions and 60 deletions
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12
src/core/evaluator.js
View file

@ -1315,20 +1315,17 @@ class PartialEvaluator {
}
parseShading({
keyObj,
shading,
resources,
localColorSpaceCache,
localShadingPatternCache,
matrix = null,
}) {
// Shadings and patterns may be referenced by the same name but the resource
// dictionary could be different so we can't use the name for the cache key.
let id = localShadingPatternCache.get(keyObj);
let id = localShadingPatternCache.get(shading);
if (!id) {
var shadingFill = Pattern.parseShading(
shading,
matrix,
this.xref,
resources,
this.handler,
@ -1337,7 +1334,7 @@ class PartialEvaluator {
);
const patternIR = shadingFill.getIR();
id = `pattern_${this.idFactory.createObjId()}`;
localShadingPatternCache.set(keyObj, id);
localShadingPatternCache.set(shading, id);
this.handler.send("obj", [id, this.pageIndex, "Pattern", patternIR]);
}
return id;
@ -1402,14 +1399,12 @@ class PartialEvaluator {
const shading = dict.get("Shading");
const matrix = dict.getArray("Matrix");
const objId = this.parseShading({
keyObj: pattern,
shading,
matrix,
resources,
localColorSpaceCache,
localShadingPatternCache,
});
operatorList.addOp(fn, ["Shading", objId]);
operatorList.addOp(fn, ["Shading", objId, matrix]);
return undefined;
}
throw new FormatError(`Unknown PatternType: ${typeNum}`);
@ -1942,7 +1937,6 @@ class PartialEvaluator {
throw new FormatError("No shading object found");
}
const patternId = self.parseShading({
keyObj: shading,
shading,
resources,
localColorSpaceCache,