Sakurai/pdf.js
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Reduces amount of used memory during PNG creation.

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This commit is contained in:
Yury Delendik 2014-08-09 15:53:05 -05:00
parent 458b69b649
commit 56f0539045
1 changed files with 55 additions and 43 deletions
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98
src/display/svg.js
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@ -30,7 +30,12 @@ function createScratchSVG(width, height) {
}
var convertImgDataToPng = (function convertImgDataToPngClosure() {
var crcTable = [];
var PNG_HEADER =
new Uint8Array([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
var CHUNK_WRAPPER_SIZE = 12;
var crcTable = new Int32Array(256);
for (var i = 0; i < 256; i++) {
var c = i;
for (var h = 0; h < 8; h++) {
@ -53,32 +58,32 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
return crc ^ -1;
}
function createPngChunk(type, data) {
var chunk = new Uint8Array(12 + data.length);
var p = 0;
function writePngChunk(type, body, data, offset) {
var p = offset;
var len = data.length;
chunk[p] = len >> 24 & 0xff;
chunk[p + 1] = len >> 16 & 0xff;
chunk[p + 2] = len >> 8 & 0xff;
chunk[p + 3] = len & 0xff;
var len = body.length;
chunk[p + 4] = type.charCodeAt(0) & 0xff;
chunk[p + 5] = type.charCodeAt(1) & 0xff;
chunk[p + 6] = type.charCodeAt(2) & 0xff;
chunk[p + 7] = type.charCodeAt(3) & 0xff;
data[p] = len >> 24 & 0xff;
data[p + 1] = len >> 16 & 0xff;
data[p + 2] = len >> 8 & 0xff;
data[p + 3] = len & 0xff;
p += 4;
chunk.set(data, 8);
data[p] = type.charCodeAt(0) & 0xff;
data[p + 1] = type.charCodeAt(1) & 0xff;
data[p + 2] = type.charCodeAt(2) & 0xff;
data[p + 3] = type.charCodeAt(3) & 0xff;
p += 4;
p = 8 + len;
data.set(body, p);
p += body.length;
var crc = crc32(chunk, 4, p);
chunk[p] = crc >> 24 & 0xff;
chunk[p + 1] = crc >> 16 & 0xff;
chunk[p + 2] = crc >> 8 & 0xff;
chunk[p + 3] = crc & 0xff;
var crc = crc32(data, offset + 4, p);
return chunk;
data[p] = crc >> 24 & 0xff;
data[p + 1] = crc >> 16 & 0xff;
data[p + 2] = crc >> 8 & 0xff;
data[p + 3] = crc & 0xff;
}
function adler32(data, start, end) {
@ -119,18 +124,26 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
throw new Error('invalid format');
}
// prefix every row with predictor 0
var literals = new Uint8Array((1 + lineSize) * height);
var offsetLiterals = 0, offsetBytes = 0;
for (var y = 0; y < height; ++y) {
literals[offsetLiterals++] = 0;
var y, i;
for (y = 0; y < height; ++y) {
literals[offsetLiterals++] = 0; // no prediction
literals.set(bytes.subarray(offsetBytes, offsetBytes + lineSize),
offsetLiterals);
offsetBytes += lineSize;
offsetLiterals += lineSize;
}
if (kind === ImageKind.GRAYSCALE_1BPP) {
for (var i = 0, ii = bytes.length; i < ii; i++) {
bytes[i] ^= 0xFF;
// inverting for B/W
offsetLiterals = 0;
for (y = 0; y < height; y++) {
offsetLiterals++; // skipping predictor
for (i = 0; i < lineSize; i++) {
literals[offsetLiterals++] ^= 0xFF;
}
}
}
@ -153,14 +166,15 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
var len = literals.length;
var maxBlockLength = 0xFFFF;
var idat = new Uint8Array(2 + len +
Math.ceil(len / maxBlockLength) * 5 + 4);
var deflateBlocks = Math.ceil(len / maxBlockLength);
var idat = new Uint8Array(2 + len + deflateBlocks * 5 + 4);
var pi = 0;
idat[pi++] = 0x78; // compression method and flags
idat[pi++] = 0x9c; // flags
var pos = 0;
while (len > maxBlockLength) {
// writing non-final DEFLATE blocks type 0 and length of 65535
idat[pi++] = 0x00;
idat[pi++] = 0xff;
idat[pi++] = 0xff;
@ -172,12 +186,12 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
len -= maxBlockLength;
}
// writing non-final DEFLATE blocks type 0
idat[pi++] = 0x01;
idat[pi++] = len & 0xff;
idat[pi++] = len >> 8 & 0xff;
idat[pi++] = (~len & 0xffff) & 0xff;
idat[pi++] = (~len & 0xffff) >> 8 & 0xff;
idat.set(literals.subarray(pos), pi);
pi += literals.length - pos;
@ -187,28 +201,26 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
idat[pi++] = adler >> 8 & 0xff;
idat[pi++] = adler & 0xff;
var chunks = [
new Uint8Array([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
createPngChunk('IHDR', ihdr),
createPngChunk('IDAT', idat),
createPngChunk('IEND', new Uint8Array(0))
];
// PNG will consists: header, IHDR+data, IDAT+data, and IEND.
var pngLength = PNG_HEADER.length + CHUNK_WRAPPER_SIZE * 3 +
ihdr.length + idat.length;
var data = new Uint8Array(pngLength);
var offset = 0;
data.set(PNG_HEADER, offset);
offset += PNG_HEADER.length;
writePngChunk('IHDR', ihdr, data, offset);
offset += CHUNK_WRAPPER_SIZE + ihdr.length;
writePngChunk('IDATA', idat, data, offset);
offset += CHUNK_WRAPPER_SIZE + idat.length;
writePngChunk('IEND', new Uint8Array(0), data, offset);
var data = [];
for (var j = 0; j < 3; j++) {
data.push.apply(data, chunks[j]);
}
data = new Uint8Array(data);
return PDFJS.createObjectURL(data, 'image/png');
}
return function convertImgDataToPng(imgData) {
var kind = (imgData.kind === undefined ?
ImageKind.GRAYSCALE_1BPP : imgData.kind);
var url = encode(imgData, kind);
if (url) {
return url;
}
return encode(imgData, kind);
};
})();