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mightyscape-1.1-deprecated/extensions/fablabchemnitz/imagetracer.js/imagetracerjs-master/nodecli/PNGReader.js
2021-04-07 00:52:32 +02:00

419 lines
10 KiB
JavaScript

/*global Uint8Array:true ArrayBuffer:true */
"use strict";
var zlib = require('zlib');
var PNG = require('./PNG');
var inflate = function(data, callback){
return zlib.inflate(new Buffer(data), callback);
};
var slice = Array.prototype.slice;
var toString = Object.prototype.toString;
function equalBytes(a, b){
if (a.length != b.length) return false;
for (var l = a.length; l--;) if (a[l] != b[l]) return false;
return true;
}
function readUInt32(buffer, offset){
return (buffer[offset] << 24) +
(buffer[offset + 1] << 16) +
(buffer[offset + 2] << 8) +
(buffer[offset + 3] << 0);
}
function readUInt16(buffer, offset){
return (buffer[offset + 1] << 8) + (buffer[offset] << 0);
}
function readUInt8(buffer, offset){
return buffer[offset] << 0;
}
function bufferToString(buffer){
var str = '';
for (var i = 0; i < buffer.length; i++){
str += String.fromCharCode(buffer[i]);
}
return str;
}
var PNGReader = function(bytes){
if (typeof bytes == 'string'){
var bts = bytes;
bytes = new Array(bts.length);
for (var i = 0, l = bts.length; i < l; i++){
bytes[i] = bts[i].charCodeAt(0);
}
} else {
var type = toString.call(bytes).slice(8, -1);
if (type == 'ArrayBuffer') bytes = new Uint8Array(bytes);
}
// current pointer
this.i = 0;
// bytes buffer
this.bytes = bytes;
// Output object
this.png = new PNG();
this.dataChunks = [];
};
PNGReader.prototype.readBytes = function(length){
var end = this.i + length;
if (end > this.bytes.length){
throw new Error('Unexpectedly reached end of file');
}
var bytes = slice.call(this.bytes, this.i, end);
this.i = end;
return bytes;
};
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#5PNG-file-signature
*/
PNGReader.prototype.decodeHeader = function(){
if (this.i !== 0){
throw new Error('file pointer should be at 0 to read the header');
}
var header = this.readBytes(8);
if (!equalBytes(header, [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A])){
throw new Error('invalid PNGReader file (bad signature)');
}
this.header = header;
};
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#5Chunk-layout
*
* length = 4 bytes
* type = 4 bytes (IHDR, PLTE, IDAT, IEND or others)
* chunk = length bytes
* crc = 4 bytes
*/
PNGReader.prototype.decodeChunk = function(){
var length = readUInt32(this.readBytes(4), 0);
if (length < 0){
throw new Error('Bad chunk length ' + (0xFFFFFFFF & length));
}
var type = bufferToString(this.readBytes(4));
var chunk = this.readBytes(length);
var crc = this.readBytes(4);
switch (type){
case 'IHDR': this.decodeIHDR(chunk); break;
case 'PLTE': this.decodePLTE(chunk); break;
case 'IDAT': this.decodeIDAT(chunk); break;
case 'IEND': this.decodeIEND(chunk); break;
}
return type;
};
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IHDR
* http://www.libpng.org/pub/png/spec/1.2/png-1.2-pdg.html#C.IHDR
*
* Width 4 bytes
* Height 4 bytes
* Bit depth 1 byte
* Colour type 1 byte
* Compression method 1 byte
* Filter method 1 byte
* Interlace method 1 byte
*/
PNGReader.prototype.decodeIHDR = function(chunk){
var png = this.png;
png.setWidth( readUInt32(chunk, 0));
png.setHeight( readUInt32(chunk, 4));
png.setBitDepth( readUInt8(chunk, 8));
png.setColorType( readUInt8(chunk, 9));
png.setCompressionMethod( readUInt8(chunk, 10));
png.setFilterMethod( readUInt8(chunk, 11));
png.setInterlaceMethod( readUInt8(chunk, 12));
};
/**
*
* http://www.w3.org/TR/PNG/#11PLTE
*/
PNGReader.prototype.decodePLTE = function(chunk){
this.png.setPalette(chunk);
};
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IDAT
*/
PNGReader.prototype.decodeIDAT = function(chunk){
// multiple IDAT chunks will concatenated
this.dataChunks.push(chunk);
};
/**
* http://www.w3.org/TR/2003/REC-PNG-20031110/#11IEND
*/
PNGReader.prototype.decodeIEND = function(){
};
/**
* Uncompress IDAT chunks
*/
PNGReader.prototype.decodePixels = function(callback){
var png = this.png;
var reader = this;
var length = 0;
var i, j, k, l;
for (l = this.dataChunks.length; l--;) length += this.dataChunks[l].length;
var data = new Buffer(length);
for (i = 0, k = 0, l = this.dataChunks.length; i < l; i++){
var chunk = this.dataChunks[i];
for (j = 0; j < chunk.length; j++) data[k++] = chunk[j];
}
inflate(data, function(err, data){
if (err) return callback(err);
try {
if (png.getInterlaceMethod() === 0){
reader.interlaceNone(data);
} else {
reader.interlaceAdam7(data);
}
} catch (e){
return callback(e);
}
callback();
});
};
// Different interlace methods
PNGReader.prototype.interlaceNone = function(data){
var png = this.png;
// bytes per pixel
var bpp = Math.max(1, png.colors * png.bitDepth / 8);
// color bytes per row
var cpr = bpp * png.width;
var pixels = new Buffer(bpp * png.width * png.height);
var scanline;
var offset = 0;
for (var i = 0; i < data.length; i += cpr + 1){
scanline = slice.call(data, i + 1, i + cpr + 1);
switch (readUInt8(data, i)){
case 0: this.unFilterNone( scanline, pixels, bpp, offset, cpr); break;
case 1: this.unFilterSub( scanline, pixels, bpp, offset, cpr); break;
case 2: this.unFilterUp( scanline, pixels, bpp, offset, cpr); break;
case 3: this.unFilterAverage(scanline, pixels, bpp, offset, cpr); break;
case 4: this.unFilterPaeth( scanline, pixels, bpp, offset, cpr); break;
default: throw new Error("unkown filtered scanline");
}
offset += cpr;
}
png.pixels = pixels;
};
PNGReader.prototype.interlaceAdam7 = function(data){
throw new Error("Adam7 interlacing is not implemented yet");
};
// Unfiltering
/**
* No filtering, direct copy
*/
PNGReader.prototype.unFilterNone = function(scanline, pixels, bpp, of, length){
for (var i = 0, to = length; i < to; i++){
pixels[of + i] = scanline[i];
}
};
/**
* The Sub() filter transmits the difference between each byte and the value
* of the corresponding byte of the prior pixel.
* Sub(x) = Raw(x) + Raw(x - bpp)
*/
PNGReader.prototype.unFilterSub = function(scanline, pixels, bpp, of, length){
var i = 0;
for (; i < bpp; i++) pixels[of + i] = scanline[i];
for (; i < length; i++){
// Raw(x) + Raw(x - bpp)
pixels[of + i] = (scanline[i] + pixels[of + i - bpp]) & 0xFF;
}
};
/**
* The Up() filter is just like the Sub() filter except that the pixel
* immediately above the current pixel, rather than just to its left, is used
* as the predictor.
* Up(x) = Raw(x) + Prior(x)
*/
PNGReader.prototype.unFilterUp = function(scanline, pixels, bpp, of, length){
var i = 0, byte, prev;
// Prior(x) is 0 for all x on the first scanline
if ((of - length) < 0) for (; i < length; i++){
pixels[of + i] = scanline[i];
} else for (; i < length; i++){
// Raw(x)
byte = scanline[i];
// Prior(x)
prev = pixels[of + i - length];
pixels[of + i] = (byte + prev) & 0xFF;
}
};
/**
* The Average() filter uses the average of the two neighboring pixels (left
* and above) to predict the value of a pixel.
* Average(x) = Raw(x) + floor((Raw(x-bpp)+Prior(x))/2)
*/
PNGReader.prototype.unFilterAverage = function(scanline, pixels, bpp, of, length){
var i = 0, byte, prev, prior;
if ((of - length) < 0){
// Prior(x) == 0 && Raw(x - bpp) == 0
for (; i < bpp; i++){
pixels[of + i] = scanline[i];
}
// Prior(x) == 0 && Raw(x - bpp) != 0 (right shift, prevent doubles)
for (; i < length; i++){
pixels[of + i] = (scanline[i] + (pixels[of + i - bpp] >> 1)) & 0xFF;
}
} else {
// Prior(x) != 0 && Raw(x - bpp) == 0
for (; i < bpp; i++){
pixels[of + i] = (scanline[i] + (pixels[of - length + i] >> 1)) & 0xFF;
}
// Prior(x) != 0 && Raw(x - bpp) != 0
for (; i < length; i++){
byte = scanline[i];
prev = pixels[of + i - bpp];
prior = pixels[of + i - length];
pixels[of + i] = (byte + (prev + prior >> 1)) & 0xFF;
}
}
};
/**
* The Paeth() filter computes a simple linear function of the three
* neighboring pixels (left, above, upper left), then chooses as predictor
* the neighboring pixel closest to the computed value. This technique is due
* to Alan W. Paeth.
* Paeth(x) = Raw(x) +
* PaethPredictor(Raw(x-bpp), Prior(x), Prior(x-bpp))
* function PaethPredictor (a, b, c)
* begin
* ; a = left, b = above, c = upper left
* p := a + b - c ; initial estimate
* pa := abs(p - a) ; distances to a, b, c
* pb := abs(p - b)
* pc := abs(p - c)
* ; return nearest of a,b,c,
* ; breaking ties in order a,b,c.
* if pa <= pb AND pa <= pc then return a
* else if pb <= pc then return b
* else return c
* end
*/
PNGReader.prototype.unFilterPaeth = function(scanline, pixels, bpp, of, length){
var i = 0, raw, a, b, c, p, pa, pb, pc, pr;
if ((of - length) < 0){
// Prior(x) == 0 && Raw(x - bpp) == 0
for (; i < bpp; i++){
pixels[of + i] = scanline[i];
}
// Prior(x) == 0 && Raw(x - bpp) != 0
// paethPredictor(x, 0, 0) is always x
for (; i < length; i++){
pixels[of + i] = (scanline[i] + pixels[of + i - bpp]) & 0xFF;
}
} else {
// Prior(x) != 0 && Raw(x - bpp) == 0
// paethPredictor(x, 0, 0) is always x
for (; i < bpp; i++){
pixels[of + i] = (scanline[i] + pixels[of + i - length]) & 0xFF;
}
// Prior(x) != 0 && Raw(x - bpp) != 0
for (; i < length; i++){
raw = scanline[i];
a = pixels[of + i - bpp];
b = pixels[of + i - length];
c = pixels[of + i - length - bpp];
p = a + b - c;
pa = Math.abs(p - a);
pb = Math.abs(p - b);
pc = Math.abs(p - c);
if (pa <= pb && pa <= pc) pr = a;
else if (pb <= pc) pr = b;
else pr = c;
pixels[of + i] = (raw + pr) & 0xFF;
}
}
};
/**
* Parse the PNG file
*
* reader.parse(options, callback)
* OR
* reader.parse(callback)
*
* OPTIONS:
* option | type | default
* ----------------------------
* data boolean true should it read the pixel data
*/
PNGReader.prototype.parse = function(options, callback){
if (typeof options == 'function') callback = options;
if (typeof options != 'object') options = {};
try {
this.decodeHeader();
while (this.i < this.bytes.length){
var type = this.decodeChunk();
// stop after IHDR chunk, or after IEND
if (type == 'IHDR' && options.data === false || type == 'IEND') break;
}
var png = this.png;
this.decodePixels(function(err){
callback(err, png);
});
} catch (e){
callback(e);
}
};
module.exports = PNGReader;