png-node.js

// Generated by CoffeeScript 1.4.0

/*
# 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.
*/


(function() {
  var PNG, fs, zlib;

  fs = require('fs');

  zlib = require('zlib');

  module.exports = PNG = (function() {

    PNG.decode = function(path, fn) {
      return fs.readFile(path, function(err, file) {
        var png;
        png = new PNG(file);
        return png.decode(function(pixels) {
          return fn(pixels);
        });
      });
    };

    PNG.load = function(path) {
      var file;
      file = fs.readFileSync(path);
      return new PNG(file);
    };

    function PNG(data) {
      var chunkSize, colors, i, index, key, section, short, text, _i, _j, _ref;
      this.data = data;
      this.pos = 8;
      this.palette = [];
      this.imgData = [];
      this.transparency = {};
      this.text = {};
      while (true) {
        chunkSize = this.readUInt32();
        section = ((function() {
          var _i, _results;
          _results = [];
          for (i = _i = 0; _i < 4; i = ++_i) {
            _results.push(String.fromCharCode(this.data[this.pos++]));
          }
          return _results;
        }).call(this)).join('');
        switch (section) {
          case 'IHDR':
            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 = _i = 0; _i < chunkSize; i = _i += 1) {
              this.imgData.push(this.data[this.pos++]);
            }
            break;
          case 'tRNS':
            this.transparency = {};
            switch (this.colorType) {
              case 3:
                this.transparency.indexed = this.read(chunkSize);
                short = 255 - this.transparency.indexed.length;
                if (short > 0) {
                  for (i = _j = 0; 0 <= short ? _j < short : _j > short; i = 0 <= short ? ++_j : --_j) {
                    this.transparency.indexed.push(255);
                  }
                }
                break;
              case 0:
                this.transparency.grayscale = this.read(chunkSize)[0];
                break;
              case 2:
                this.transparency.rgb = this.read(chunkSize);
            }
            break;
          case 'tEXt':
            text = this.read(chunkSize);
            index = text.indexOf(0);
            key = String.fromCharCode.apply(String, text.slice(0, index));
            this.text[key] = String.fromCharCode.apply(String, text.slice(index + 1));
            break;
          case 'IEND':
            this.colors = (function() {
              switch (this.colorType) {
                case 0:
                case 3:
                case 4:
                  return 1;
                case 2:
                case 6:
                  return 3;
              }
            }).call(this);
            this.hasAlphaChannel = (_ref = this.colorType) === 4 || _ref === 6;
            colors = this.colors + (this.hasAlphaChannel ? 1 : 0);
            this.pixelBitlength = this.bits * colors;
            this.colorSpace = (function() {
              switch (this.colors) {
                case 1:
                  return 'DeviceGray';
                case 3:
                  return 'DeviceRGB';
              }
            }).call(this);
            this.imgData = new Buffer(this.imgData);
            return;
          default:
            this.pos += chunkSize;
        }
        this.pos += 4;
        if (this.pos > this.data.length) {
          throw new Error("Incomplete or corrupt PNG file");
        }
      }
      return;
    }

    PNG.prototype.read = function(bytes) {
      var i, _i, _results;
      _results = [];
      for (i = _i = 0; 0 <= bytes ? _i < bytes : _i > bytes; i = 0 <= bytes ? ++_i : --_i) {
        _results.push(this.data[this.pos++]);
      }
      return _results;
    };

    PNG.prototype.readUInt32 = function() {
      var b1, b2, b3, b4;
      b1 = this.data[this.pos++] << 24;
      b2 = this.data[this.pos++] << 16;
      b3 = this.data[this.pos++] << 8;
      b4 = this.data[this.pos++];
      return b1 | b2 | b3 | b4;
    };

    PNG.prototype.readUInt16 = function() {
      var b1, b2;
      b1 = this.data[this.pos++] << 8;
      b2 = this.data[this.pos++];
      return b1 | b2;
    };

    PNG.prototype.decodePixels = function(fn) {
      var _this = this;
      return zlib.inflate(this.imgData, function(err, data) {
        var byte, c, col, i, left, length, p, pa, paeth, pb, pc, pixelBytes, pixels, pos, row, scanlineLength, upper, upperLeft, _i, _j, _k, _l, _m;
        if (err) {
          throw err;
        }
        pixelBytes = _this.pixelBitlength / 8;
        scanlineLength = pixelBytes * _this.width;
        pixels = new Buffer(scanlineLength * _this.height);
        length = data.length;
        row = 0;
        pos = 0;
        c = 0;
        while (pos < length) {
          switch (data[pos++]) {
            case 0:
              for (i = _i = 0; _i < scanlineLength; i = _i += 1) {
                pixels[c++] = data[pos++];
              }
              break;
            case 1:
              for (i = _j = 0; _j < scanlineLength; i = _j += 1) {
                byte = data[pos++];
                left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
                pixels[c++] = (byte + left) % 256;
              }
              break;
            case 2:
              for (i = _k = 0; _k < scanlineLength; i = _k += 1) {
                byte = data[pos++];
                col = (i - (i % pixelBytes)) / pixelBytes;
                upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
                pixels[c++] = (upper + byte) % 256;
              }
              break;
            case 3:
              for (i = _l = 0; _l < scanlineLength; i = _l += 1) {
                byte = data[pos++];
                col = (i - (i % pixelBytes)) / pixelBytes;
                left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
                upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
                pixels[c++] = (byte + Math.floor((left + upper) / 2)) % 256;
              }
              break;
            case 4:
              for (i = _m = 0; _m < scanlineLength; i = _m += 1) {
                byte = data[pos++];
                col = (i - (i % pixelBytes)) / pixelBytes;
                left = i < pixelBytes ? 0 : pixels[c - pixelBytes];
                if (row === 0) {
                  upper = upperLeft = 0;
                } else {
                  upper = pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)];
                  upperLeft = col && pixels[(row - 1) * scanlineLength + (col - 1) * pixelBytes + (i % pixelBytes)];
                }
                p = left + upper - upperLeft;
                pa = Math.abs(p - left);
                pb = Math.abs(p - upper);
                pc = Math.abs(p - upperLeft);
                if (pa <= pb && pa <= pc) {
                  paeth = left;
                } else if (pb <= pc) {
                  paeth = upper;
                } else {
                  paeth = upperLeft;
                }
                pixels[c++] = (byte + paeth) % 256;
              }
              break;
            default:
              throw new Error("Invalid filter algorithm: " + data[pos - 1]);
          }
          row++;
        }
        return fn(pixels);
      });
    };

    PNG.prototype.decodePalette = function() {
      var c, i, length, palette, pos, ret, transparency, _i, _ref, _ref1;
      palette = this.palette;
      transparency = this.transparency.indexed || [];
      ret = new Buffer(transparency.length + palette.length);
      pos = 0;
      length = palette.length;
      c = 0;
      for (i = _i = 0, _ref = palette.length; _i < _ref; i = _i += 3) {
        ret[pos++] = palette[i];
        ret[pos++] = palette[i + 1];
        ret[pos++] = palette[i + 2];
        ret[pos++] = (_ref1 = transparency[c++]) != null ? _ref1 : 255;
      }
      return ret;
    };

    PNG.prototype.copyToImageData = function(imageData, pixels) {
      var alpha, colors, data, i, input, j, k, length, palette, v, _ref;
      colors = this.colors;
      palette = null;
      alpha = this.hasAlphaChannel;
      if (this.palette.length) {
        palette = (_ref = this._decodedPalette) != null ? _ref : this._decodedPalette = this.decodePalette();
        colors = 4;
        alpha = true;
      }
      data = (imageData != null ? imageData.data : void 0) || imageData;
      length = data.length;
      input = palette || pixels;
      i = j = 0;
      if (colors === 1) {
        while (i < length) {
          k = palette ? pixels[i / 4] * 4 : j;
          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;
        }
      }
    };

    PNG.prototype.decode = function(fn) {
      var ret,
        _this = this;
      ret = new Buffer(this.width * this.height * 4);
      return this.decodePixels(function(pixels) {
        _this.copyToImageData(ret, pixels);
        return fn(ret);
      });
    };

    return PNG;

  })();

}).call(this);