You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
402 lines
12 KiB
402 lines
12 KiB
/*
|
|
* MIT LICENSE
|
|
* Copyright (c) 2011 Devon Govett
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining a copy of this
|
|
* software and associated documentation files (the "Software"), to deal in the Software
|
|
* without restriction, including without limitation the rights to use, copy, modify, merge,
|
|
* publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
|
|
* to whom the Software is furnished to do so, subject to the following conditions:
|
|
*
|
|
* The above copyright notice and this permission notice shall be included in all copies or
|
|
* substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
|
|
* BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
|
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
|
|
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
|
|
*/
|
|
|
|
const fs = require('fs');
|
|
const zlib = require('zlib');
|
|
|
|
module.exports = class PNG {
|
|
static decode(path, fn) {
|
|
return fs.readFile(path, function(err, file) {
|
|
const png = new PNG(file);
|
|
return png.decode(pixels => fn(pixels));
|
|
});
|
|
}
|
|
|
|
static load(path) {
|
|
const file = fs.readFileSync(path);
|
|
return new PNG(file);
|
|
}
|
|
|
|
constructor(data) {
|
|
let i;
|
|
this.data = data;
|
|
this.pos = 8; // Skip the default header
|
|
|
|
this.palette = [];
|
|
this.imgData = [];
|
|
this.transparency = {};
|
|
this.text = {};
|
|
|
|
while (true) {
|
|
const chunkSize = this.readUInt32();
|
|
let section = '';
|
|
for (i = 0; i < 4; i++) {
|
|
section += String.fromCharCode(this.data[this.pos++]);
|
|
}
|
|
|
|
switch (section) {
|
|
case 'IHDR':
|
|
// we can grab interesting values from here (like width, height, etc)
|
|
this.width = this.readUInt32();
|
|
this.height = this.readUInt32();
|
|
this.bits = this.data[this.pos++];
|
|
this.colorType = this.data[this.pos++];
|
|
this.compressionMethod = this.data[this.pos++];
|
|
this.filterMethod = this.data[this.pos++];
|
|
this.interlaceMethod = this.data[this.pos++];
|
|
break;
|
|
|
|
case 'PLTE':
|
|
this.palette = this.read(chunkSize);
|
|
break;
|
|
|
|
case 'IDAT':
|
|
for (i = 0; i < chunkSize; i++) {
|
|
this.imgData.push(this.data[this.pos++]);
|
|
}
|
|
break;
|
|
|
|
case 'tRNS':
|
|
// This chunk can only occur once and it must occur after the
|
|
// PLTE chunk and before the IDAT chunk.
|
|
this.transparency = {};
|
|
switch (this.colorType) {
|
|
case 3:
|
|
// Indexed color, RGB. Each byte in this chunk is an alpha for
|
|
// the palette index in the PLTE ("palette") chunk up until the
|
|
// last non-opaque entry. Set up an array, stretching over all
|
|
// palette entries which will be 0 (opaque) or 1 (transparent).
|
|
this.transparency.indexed = this.read(chunkSize);
|
|
var short = 255 - this.transparency.indexed.length;
|
|
if (short > 0) {
|
|
for (i = 0; i < short; i++) {
|
|
this.transparency.indexed.push(255);
|
|
}
|
|
}
|
|
break;
|
|
case 0:
|
|
// Greyscale. Corresponding to entries in the PLTE chunk.
|
|
// Grey is two bytes, range 0 .. (2 ^ bit-depth) - 1
|
|
this.transparency.grayscale = this.read(chunkSize)[0];
|
|
break;
|
|
case 2:
|
|
// True color with proper alpha channel.
|
|
this.transparency.rgb = this.read(chunkSize);
|
|
break;
|
|
}
|
|
break;
|
|
|
|
case 'tEXt':
|
|
var text = this.read(chunkSize);
|
|
var index = text.indexOf(0);
|
|
var key = String.fromCharCode.apply(String, text.slice(0, index));
|
|
this.text[key] = String.fromCharCode.apply(
|
|
String,
|
|
text.slice(index + 1)
|
|
);
|
|
break;
|
|
|
|
case 'IEND':
|
|
// we've got everything we need!
|
|
switch (this.colorType) {
|
|
case 0:
|
|
case 3:
|
|
case 4:
|
|
this.colors = 1;
|
|
break;
|
|
case 2:
|
|
case 6:
|
|
this.colors = 3;
|
|
break;
|
|
}
|
|
|
|
this.hasAlphaChannel = [4, 6].includes(this.colorType);
|
|
var colors = this.colors + (this.hasAlphaChannel ? 1 : 0);
|
|
this.pixelBitlength = this.bits * colors;
|
|
|
|
switch (this.colors) {
|
|
case 1:
|
|
this.colorSpace = 'DeviceGray';
|
|
break;
|
|
case 3:
|
|
this.colorSpace = 'DeviceRGB';
|
|
break;
|
|
}
|
|
|
|
this.imgData = new Buffer(this.imgData);
|
|
return;
|
|
break;
|
|
|
|
default:
|
|
// unknown (or unimportant) section, skip it
|
|
this.pos += chunkSize;
|
|
}
|
|
|
|
this.pos += 4; // Skip the CRC
|
|
|
|
if (this.pos > this.data.length) {
|
|
throw new Error('Incomplete or corrupt PNG file');
|
|
}
|
|
}
|
|
}
|
|
|
|
read(bytes) {
|
|
const result = new Array(bytes);
|
|
for (let i = 0; i < bytes; i++) {
|
|
result[i] = this.data[this.pos++];
|
|
}
|
|
return result;
|
|
}
|
|
|
|
readUInt32() {
|
|
const b1 = this.data[this.pos++] << 24;
|
|
const b2 = this.data[this.pos++] << 16;
|
|
const b3 = this.data[this.pos++] << 8;
|
|
const b4 = this.data[this.pos++];
|
|
return b1 | b2 | b3 | b4;
|
|
}
|
|
|
|
readUInt16() {
|
|
const b1 = this.data[this.pos++] << 8;
|
|
const b2 = this.data[this.pos++];
|
|
return b1 | b2;
|
|
}
|
|
|
|
decodePixels(fn) {
|
|
return zlib.inflate(this.imgData, (err, data) => {
|
|
if (err) {
|
|
throw err;
|
|
}
|
|
|
|
const { width, height } = this;
|
|
const pixelBytes = this.pixelBitlength / 8;
|
|
|
|
const pixels = new Buffer(width * height * pixelBytes);
|
|
const { length } = data;
|
|
let pos = 0;
|
|
|
|
function pass(x0, y0, dx, dy, singlePass = false) {
|
|
const w = Math.ceil((width - x0) / dx);
|
|
const h = Math.ceil((height - y0) / dy);
|
|
const scanlineLength = pixelBytes * w;
|
|
const buffer = singlePass ? pixels : new Buffer(scanlineLength * h);
|
|
let row = 0;
|
|
let c = 0;
|
|
while (row < h && pos < length) {
|
|
var byte, col, i, left, upper;
|
|
switch (data[pos++]) {
|
|
case 0: // None
|
|
for (i = 0; i < scanlineLength; i++) {
|
|
buffer[c++] = data[pos++];
|
|
}
|
|
break;
|
|
|
|
case 1: // Sub
|
|
for (i = 0; i < scanlineLength; i++) {
|
|
byte = data[pos++];
|
|
left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
|
|
buffer[c++] = (byte + left) % 256;
|
|
}
|
|
break;
|
|
|
|
case 2: // Up
|
|
for (i = 0; i < scanlineLength; i++) {
|
|
byte = data[pos++];
|
|
col = (i - (i % pixelBytes)) / pixelBytes;
|
|
upper =
|
|
row &&
|
|
buffer[
|
|
(row - 1) * scanlineLength +
|
|
col * pixelBytes +
|
|
(i % pixelBytes)
|
|
];
|
|
buffer[c++] = (upper + byte) % 256;
|
|
}
|
|
break;
|
|
|
|
case 3: // Average
|
|
for (i = 0; i < scanlineLength; i++) {
|
|
byte = data[pos++];
|
|
col = (i - (i % pixelBytes)) / pixelBytes;
|
|
left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
|
|
upper =
|
|
row &&
|
|
buffer[
|
|
(row - 1) * scanlineLength +
|
|
col * pixelBytes +
|
|
(i % pixelBytes)
|
|
];
|
|
buffer[c++] = (byte + Math.floor((left + upper) / 2)) % 256;
|
|
}
|
|
break;
|
|
|
|
case 4: // Paeth
|
|
for (i = 0; i < scanlineLength; i++) {
|
|
var paeth, upperLeft;
|
|
byte = data[pos++];
|
|
col = (i - (i % pixelBytes)) / pixelBytes;
|
|
left = i < pixelBytes ? 0 : buffer[c - pixelBytes];
|
|
|
|
if (row === 0) {
|
|
upper = upperLeft = 0;
|
|
} else {
|
|
upper =
|
|
buffer[
|
|
(row - 1) * scanlineLength +
|
|
col * pixelBytes +
|
|
(i % pixelBytes)
|
|
];
|
|
upperLeft =
|
|
col &&
|
|
buffer[
|
|
(row - 1) * scanlineLength +
|
|
(col - 1) * pixelBytes +
|
|
(i % pixelBytes)
|
|
];
|
|
}
|
|
|
|
const p = left + upper - upperLeft;
|
|
const pa = Math.abs(p - left);
|
|
const pb = Math.abs(p - upper);
|
|
const pc = Math.abs(p - upperLeft);
|
|
|
|
if (pa <= pb && pa <= pc) {
|
|
paeth = left;
|
|
} else if (pb <= pc) {
|
|
paeth = upper;
|
|
} else {
|
|
paeth = upperLeft;
|
|
}
|
|
|
|
buffer[c++] = (byte + paeth) % 256;
|
|
}
|
|
break;
|
|
|
|
default:
|
|
throw new Error(`Invalid filter algorithm: ${data[pos - 1]}`);
|
|
}
|
|
|
|
if (!singlePass) {
|
|
let pixelsPos = ((y0 + row * dy) * width + x0) * pixelBytes;
|
|
let bufferPos = row * scanlineLength;
|
|
for (i = 0; i < w; i++) {
|
|
for (let j = 0; j < pixelBytes; j++)
|
|
pixels[pixelsPos++] = buffer[bufferPos++];
|
|
pixelsPos += (dx - 1) * pixelBytes;
|
|
}
|
|
}
|
|
|
|
row++;
|
|
}
|
|
}
|
|
|
|
if (this.interlaceMethod === 1) {
|
|
/*
|
|
1 6 4 6 2 6 4 6
|
|
7 7 7 7 7 7 7 7
|
|
5 6 5 6 5 6 5 6
|
|
7 7 7 7 7 7 7 7
|
|
3 6 4 6 3 6 4 6
|
|
7 7 7 7 7 7 7 7
|
|
5 6 5 6 5 6 5 6
|
|
7 7 7 7 7 7 7 7
|
|
*/
|
|
pass(0, 0, 8, 8); // 1
|
|
pass(4, 0, 8, 8); // 2
|
|
pass(0, 4, 4, 8); // 3
|
|
pass(2, 0, 4, 4); // 4
|
|
pass(0, 2, 2, 4); // 5
|
|
pass(1, 0, 2, 2); // 6
|
|
pass(0, 1, 1, 2); // 7
|
|
} else {
|
|
pass(0, 0, 1, 1, true);
|
|
}
|
|
|
|
return fn(pixels);
|
|
});
|
|
}
|
|
|
|
decodePalette() {
|
|
const { palette } = this;
|
|
const { length } = palette;
|
|
const transparency = this.transparency.indexed || [];
|
|
const ret = new Buffer(transparency.length + length);
|
|
let pos = 0;
|
|
let c = 0;
|
|
|
|
for (let i = 0; i < length; i += 3) {
|
|
var left;
|
|
ret[pos++] = palette[i];
|
|
ret[pos++] = palette[i + 1];
|
|
ret[pos++] = palette[i + 2];
|
|
ret[pos++] = (left = transparency[c++]) != null ? left : 255;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
copyToImageData(imageData, pixels) {
|
|
let j, k;
|
|
let { colors } = this;
|
|
let palette = null;
|
|
let alpha = this.hasAlphaChannel;
|
|
|
|
if (this.palette.length) {
|
|
palette =
|
|
this._decodedPalette || (this._decodedPalette = this.decodePalette());
|
|
colors = 4;
|
|
alpha = true;
|
|
}
|
|
|
|
const data = imageData.data || imageData;
|
|
const { length } = data;
|
|
const input = palette || pixels;
|
|
let i = (j = 0);
|
|
|
|
if (colors === 1) {
|
|
while (i < length) {
|
|
k = palette ? pixels[i / 4] * 4 : j;
|
|
const v = input[k++];
|
|
data[i++] = v;
|
|
data[i++] = v;
|
|
data[i++] = v;
|
|
data[i++] = alpha ? input[k++] : 255;
|
|
j = k;
|
|
}
|
|
} else {
|
|
while (i < length) {
|
|
k = palette ? pixels[i / 4] * 4 : j;
|
|
data[i++] = input[k++];
|
|
data[i++] = input[k++];
|
|
data[i++] = input[k++];
|
|
data[i++] = alpha ? input[k++] : 255;
|
|
j = k;
|
|
}
|
|
}
|
|
}
|
|
|
|
decode(fn) {
|
|
const ret = new Buffer(this.width * this.height * 4);
|
|
return this.decodePixels(pixels => {
|
|
this.copyToImageData(ret, pixels);
|
|
return fn(ret);
|
|
});
|
|
}
|
|
};
|