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Implement Decode entry in Indexed images

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Jani Pehkonen 2019-01-22 19:59:36 +02:00
parent f26129de26
commit 26121177ab
7 changed files with 37 additions and 14 deletions
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9
src/core/image.js
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@ -169,18 +169,21 @@ var PDFImage = (function PDFImageClosure() {
this.decode = dict.getArray('Decode', 'D');
this.needsDecode = false;
if (this.decode &&
((this.colorSpace && !this.colorSpace.isDefaultDecode(this.decode)) ||
((this.colorSpace &&
!this.colorSpace.isDefaultDecode(this.decode, bitsPerComponent)) ||
(isMask && !ColorSpace.isDefaultDecode(this.decode, 1)))) {
this.needsDecode = true;
// Do some preprocessing to avoid more math.
var max = (1 << bitsPerComponent) - 1;
this.decodeCoefficients = [];
this.decodeAddends = [];
const isIndexed = this.colorSpace && this.colorSpace.name === 'Indexed';
for (var i = 0, j = 0; i < this.decode.length; i += 2, ++j) {
var dmin = this.decode[i];
var dmax = this.decode[i + 1];
this.decodeCoefficients[j] = dmax - dmin;
this.decodeAddends[j] = max * dmin;
this.decodeCoefficients[j] = isIndexed ? ((dmax - dmin) / max) :
(dmax - dmin);
this.decodeAddends[j] = isIndexed ? dmin : (max * dmin);
}
}