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Move the default decode to logic to the colorspace.

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This commit is contained in:
Brendan Dahl 2011-12-13 14:35:46 -08:00
parent 55bbcbc664
commit ff1d804fd7
2 changed files with 56 additions and 29 deletions
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45
src/image.js
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@ -25,11 +25,10 @@ var PDFImage = (function PDFImageClosure() {
}
}
/**
* Decode and clamp a value.
* Decode and clamp a value. The formula is different from the spec because we
* don't decode to float range [0,1], we decode it in the [0,max] range.
*/
function decode(value, addend, coefficient, max) {
// This formula is different from the spec because we don't decode to
// float range [0,1], we decode it in the [0,max] range.
function decodeAndClamp(value, addend, coefficient, max) {
value = addend + value * coefficient;
// Clamp the value to the range
return value < 0 ? 0 : value > max ? max : value;
@ -79,7 +78,10 @@ var PDFImage = (function PDFImageClosure() {
}
this.decode = dict.get('Decode', 'D');
if (this.decode && !this.hasDefaultDecode()) {
this.needsDecode = false;
if (this.decode && this.colorSpace &&
!this.colorSpace.isDefaultDecode(this.decode)) {
this.needsDecode = true;
// Do some preprocessing to avoid more math.
var max = (1 << bitsPerComponent) - 1;
this.decodeCoefficients = [];
@ -128,12 +130,13 @@ var PDFImage = (function PDFImageClosure() {
PDFImage.prototype = {
getComponents: function getComponents(buffer) {
var bpc = this.bpc;
var defaultDecode = this.hasDefaultDecode();
var needsDecode = this.needsDecode;
var decodeMap = this.decode;
if (decodeMap) console.time('getComps');
// This image doesn't require extra work
if (bpc == 8 && defaultDecode)
// This image doesn't require any extra work.
if (bpc == 8 && !needsDecode)
return buffer;
var bufferLength = buffer.length;
var width = this.width;
var height = this.height;
@ -145,7 +148,7 @@ var PDFImage = (function PDFImageClosure() {
bpc <= 16 ? new Uint16Array(length) : new Uint32Array(length);
var rowComps = width * numComps;
var decodeAddends, decodeCoefficients;
if (!defaultDecode) {
if (needsDecode) {
decodeAddends = this.decodeAddends;
decodeCoefficients = this.decodeCoefficients;
}
@ -156,7 +159,7 @@ var PDFImage = (function PDFImageClosure() {
for (var i = 0, ii = length; i < ii; ++i) {
var compIndex = i % numComps;
var value = buffer[i];
value = decode(value, decodeAddends[compIndex],
value = decodeAndClamp(value, decodeAddends[compIndex],
decodeCoefficients[compIndex], max);
output[i] = value;
}
@ -201,9 +204,9 @@ var PDFImage = (function PDFImageClosure() {
var remainingBits = bits - bpc;
var value = buf >> remainingBits;
if (!defaultDecode) {
if (needsDecode) {
var compIndex = i % numComps;
value = decode(value, decodeAddends[compIndex],
value = decodeAndClamp(value, decodeAddends[compIndex],
decodeCoefficients[compIndex], max);
}
output[i] = value;
@ -304,22 +307,6 @@ var PDFImage = (function PDFImageClosure() {
getImageBytes: function getImageBytes(length) {
this.image.reset();
return this.image.getBytes(length);
},
hasDefaultDecode: function hasDefaultDecode() {
// TODO lab color as a way different decode map
if (!this.decode)
return true;
var numComps = this.numComps;
var decode = this.decode;
if (numComps * 2 !== decode.length) {
warning('The decode map is not the correct length');
return true;
}
for (var i = 0, ii = decode.length; i < ii; i += 2) {
if (decode[i] != 0 || decode[i + 1] != 1)
return false;
}
return true;
}
};
return PDFImage;