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| // file: node-zlibPNG
//
// Implements a PNG encoder using only the built-in zlib module.
// No other dependencies.
//
// This is part of the bwip-js project available at:
//
// http://metafloor.github.io/bwip-js
//
// Copyright (c) 2011-2016 Mark Warren
//
// The MIT License
//
// 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.
var zlib = require('zlib');
// Statically calculate the crc lookup table
var crcCalc = [];
(function() {
for (var i = 0; i < 256; i++) {
var c = i;
for (var j = 0; j < 8; j++) {
if (c & 1) {
c = 0xedb88320 ^ (c >>> 1);
} else {
c = c >>> 1;
}
}
crcCalc[i] = c;
}
})();
// bgcolor is optional.
module.exports = function (width, height, bgcolor) {
width = width | 0;
height = height | 0;
var TEXT = "Software\0bwip-js.metafloor.com";
var _pixels = []; // Cannot use Uint32Array - need undefined elts
var _palette = { 0:0 }; // Index-0 is always the background color
var _ncolors = 1; // The background color
var _cmap = []; // Only if ncolors <= 256
var _trans = false; // Has transparency?
var _gray = false; // Has only grays?
var _nset = 0; // Number of set pixels
// Background color does not support alpha-channel
if (bgcolor !== undefined) {
bgcolor = (0xff000000|bgcolor) >>> 0;
_gray = ((bgcolor >>> 16) & 0xff) == (bgcolor & 0xff) &&
((bgcolor >>> 8) & 0xff) == (bgcolor & 0xff);
_nset = width * height;
_palette = {};
_palette[bgcolor] = 0;
for (var i = 0; i < _nset; i++)
_pixels[i] = bgcolor;
}
// Set a pixel to the given RGB color
this.setRGB = function(x, y, c) {
this.set(x, y, (0xff000000|c) >>> 0);
}
// Set a pixel to the given ARGB color
this.set = function(x, y, clr) {
var cur = _pixels[y * width + x];
if (cur === undefined) {
_nset++;
} else {
// alpha-blend with the existing color
var cura = (cur >>> 24) / 255;
var curr = (cur >>> 16) & 0xff;
var curg = (cur >>> 8) & 0xff;
var curb = cur & 0xff;
var clra = (clr >>> 24) / 255;
var clrr = (clr >>> 16) & 0xff;
var clrg = (clr >>> 8) & 0xff;
var clrb = clr & 0xff;
var newa = clra + cura * (1 - clra); // new alpha 0.0 - 1.0
if (!newa) {
clr = 0; // fully transparent
} else {
var newr = ((clrr * clra + curr * cura * (1 - clra)) / newa)|0;
var newg = ((clrg * clra + curg * cura * (1 - clra)) / newa)|0;
var newb = ((clrb * clra + curb * cura * (1 - clra)) / newa)|0;
clr = ((((newa * 255)|0)<<24) | (newr<<16) | (newg<<8) | newb) >>> 0;
}
}
_gray = _gray &&
((clr >>> 16) & 0xff) == (clr & 0xff) &&
((clr >>> 8) & 0xff) == (clr & 0xff);
_trans = _trans || (clr >>> 24) < 255;
// If we exceed 256 unique colors, we automatically switch to 32-bit
// PNG (TrueColor with alpha)
if (_ncolors <= 256 && _palette[clr] === undefined)
_palette[clr] = _ncolors++;
_pixels[y * width + x] = clr;
}
this.get = function(x, y) {
return _pixels[y * width + x] || 0;
}
// Return a PNG in a Buffer
// callback(e, png)
this.render = function(callback) {
// If not all pixels were set, the 0-alpha background shows through
_trans = _trans || _nset < width * height;
// DEFLATE the image data based on color depth
var image;
if (_gray && !_trans) {
image = toGrayScale();
} else if (_ncolors <= 256) {
image = toPalette();
} else if (_gray) {
image = toGrayAlpha();
} else {
image = _trans ? toTrueAlpha() : toTrueColor();
}
// v0.12 only...
//zlib.deflate(image, {
// chunkSize: 32 * 1024,
// level : zlib.Z_DEFAULT_COMPRESSION,
// strategy: zlib.Z_DEFAULT_STRATEGY
// }, returnPNG);
// v0.10+ compatible
var bufs = [];
var blen = 0;
var deflator = zlib.createDeflate({
chunkSize: 32 * 1024,
level : zlib.Z_DEFAULT_COMPRESSION,
strategy: zlib.Z_DEFAULT_STRATEGY });
deflator.on('error', callback);
deflator.on('data', function(data) { bufs.push(data); blen += data.length; });
deflator.on('end', function() { returnPNG(Buffer.concat(bufs, blen)); });
deflator.end(image);
function returnPNG(data) {
var length = 8 + 12 + 13 + // PNG Header + IDHR chunk
12 + TEXT.length + // tEXt
12 + data.length + // IDAT
12; // IEND
if (_gray && !_trans) {
// no extra chunks
} else if (_ncolors <= 256) {
length += 12 + 3*_ncolors; // PLTE
if (_trans)
length += 12 + _ncolors; // tRNS
}
// Emulate a byte-stream
var png = new Buffer(length);
var pngoff = 0; // running offset into the png buffer
write('\x89PNG\x0d\x0a\x1a\x0a'); // PNG file header
writeIHDR();
writeTEXT();
if (_gray && !_trans) {
// no extra chunks
} else if (_ncolors <= 256) {
writePLTE();
if (_trans)
writeTRNS();
}
writeIDAT();
writeIEND();
// Success
callback(null, png);
function writeIHDR() {
write32(13); // chunk length
var crcoff = pngoff;
write('IHDR');
write32(width);
write32(height);
write8(8); // bit depth
if (_gray && !_trans) {
write8(0); // grayscale
} else if (_ncolors <= 256) {
write8(3); // rgb palette
} else if (_gray) {
write8(4); // grayscale with alpha
} else if (_trans) {
write8(6); // truecolor with alpha
} else {
write8(2); // truecolor
}
write8(0); // compression default
write8(0); // filter default
write8(0); // no interlace
writeCRC(crcoff);
}
function writeTEXT() {
write32(TEXT.length); // chunk length
var crcoff = pngoff;
write('tEXt');
write(TEXT);
writeCRC(crcoff);
}
function writePLTE() {
write32(_ncolors*3); // chunk length
var crcoff = pngoff;
write('PLTE');
for (var i = 0; i < _cmap.length; i++) {
var c = _cmap[i];
write8((c >>> 16) & 0xff);
write8((c >>> 8) & 0xff);
write8(c & 0xff);
}
writeCRC(crcoff);
}
function writeTRNS() {
write32(_ncolors); // chunk length
var crcoff = pngoff;
write('tRNS');
for (var i = 0; i < _cmap.length; i++) {
write8((_cmap[i] >>> 24) & 0xff);
}
writeCRC(crcoff);
}
function writeIDAT() {
write32(data.length); // chunk length
var crcoff = pngoff;
write('IDAT');
data.copy(png, pngoff);
pngoff += data.length;
writeCRC(crcoff);
}
function writeIEND() {
write32(0); // chunk length;
var crcoff = pngoff;
write('IEND');
writeCRC(crcoff);
}
function write(s) {
png.write(s, pngoff, 'binary');
pngoff += s.length;
}
function write32(v) {
png.writeUInt32BE(v, pngoff);
pngoff += 4;
}
function write16(v) {
png.writeUInt16BE(v, pngoff);
pngoff += 2;
}
function write8(v) {
png[pngoff++] = v;
}
function writeCRC(off) {
var crc = -1;
while (off < pngoff) {
crc = crcCalc[(crc ^ png[off++]) & 0xff] ^ (crc >>> 8);
}
write32((crc ^ -1) >>> 0); // >>> 0 casts to Uint32
}
}
}
// Convert the image to grayscale
function toGrayScale() {
// One extra byte per row for the filter type
var buf = new Buffer((width + 1) * height);
var pos = 0;
for (var y = 0; y < height; y++) {
var row = y * width;
buf[pos++] = 0; // Row filters not implemented
for (var x = 0; x < width; x++) {
buf[pos++] = (_pixels[row + x] || 0) & 0xff;
}
}
return buf;
}
// Convert the image to grayscale with alpha
function toGrayAlpha() {
// One extra byte per row for the filter type
var buf = new Buffer((width * 2 + 1) * height);
var pos = 0;
for (var y = 0; y < height; y++) {
var row = y * width;
buf[pos++] = 0; // Row filters not implemented
for (var x = 0; x < width; x++) {
var c = _pixels[row + x] || 0;
buf[pos++] = c & 0xff; // gray
buf[pos++] = (c >>> 24) & 0xff; // alpha
}
}
return buf;
}
// Convert the image data to indexed palette
function toPalette() {
// Convert the palette object to the color map
for (var color in _palette) {
_cmap[_palette[color]] = color;
}
// One extra byte per row for the filter type
var buf = new Buffer((width + 1) * height);
var pos = 0;
for (var y = 0; y < height; y++) {
var row = y * width;
buf[pos++] = 0; // Row filters not implemented
for (var x = 0; x < width; x++) {
buf[pos++] = _palette[_pixels[row + x] || 0];
}
}
return buf;
}
// Convert the image data to TrueColor
function toTrueColor() {
// One extra byte per row for the filter type
var buf = new Buffer((width * 3 + 1) * height);
var pos = 0;
for (var y = 0; y < height; y++) {
var row = y * width;
buf[pos++] = 0; // Row filters not implemented
for (var x = 0; x < width; x++) {
var c = _pixels[row + x] || 0;
buf[pos++] = (c >>> 16) & 0xff; // red
buf[pos++] = (c >>> 8) & 0xff; // green
buf[pos++] = c & 0xff; // blue
}
}
return buf;
}
// Convert the image data to TrueColor with alpha
function toTrueAlpha() {
// One extra byte per row for the filter type
var buf = new Buffer((width * 4 + 1) * height);
var pos = 0;
for (var y = 0; y < height; y++) {
var row = y * width;
buf[pos++] = 0; // Row filters not implemented
for (var x = 0; x < width; x++) {
var c = _pixels[row + x] || 0;
buf[pos++] = (c >>> 16) & 0xff; // red
buf[pos++] = (c >>> 8) & 0xff; // green
buf[pos++] = c & 0xff; // blue
buf[pos++] = (c >>> 24) & 0xff; // alpha
}
}
return buf;
}
}
|