jspdf.plugin.png_support.js

/**@preserve
 *  ==================================================================== 
 * jsPDF PNG PlugIn
 * Copyright (c) 2014 James Robb, https://github.com/jamesbrobb
 * 
 * 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(jsPDFAPI) {
'use strict'
	
	/*
	 * @see http://www.w3.org/TR/PNG-Chunks.html
	 * 
	 Color    Allowed      Interpretation
	 Type     Bit Depths
	   
	   0       1,2,4,8,16  Each pixel is a grayscale sample.
	   
	   2       8,16        Each pixel is an R,G,B triple.
	   
	   3       1,2,4,8     Each pixel is a palette index;
	                       a PLTE chunk must appear.
	   
	   4       8,16        Each pixel is a grayscale sample,
	                       followed by an alpha sample.
	   
	   6       8,16        Each pixel is an R,G,B triple,
	                       followed by an alpha sample.
	*/
	
	/*
	 * PNG filter method types
	 * 
	 * @see http://www.w3.org/TR/PNG-Filters.html
	 * @see http://www.libpng.org/pub/png/book/chapter09.html
	 * 
	 * This is what the value 'Predictor' in decode params relates to
	 * 
	 * 15 is "optimal prediction", which means the prediction algorithm can change from line to line.
	 * In that case, you actually have to read the first byte off each line for the prediction algorthim (which should be 0-4, corresponding to PDF 10-14) and select the appropriate unprediction algorithm based on that byte.
	 *
	   0       None
	   1       Sub
	   2       Up
	   3       Average
	   4       Paeth
	 */
	
	var doesNotHavePngJS = function() {
		return typeof PNG !== 'function' || typeof FlateStream !== 'function';
	}
	, canCompress = function(value) {
		return value !== jsPDFAPI.image_compression.NONE && hasCompressionJS();
	}
	, hasCompressionJS = function() {
		var inst = typeof Deflater === 'function';
		if(!inst)
			throw new Error("requires deflate.js for compression")
		return inst;
	}
	, compressBytes = function(bytes, lineLength, colorsPerPixel, compression) {
		
		var level = 5,
			filter_method = filterUp;
		
		switch(compression) {
		
			case jsPDFAPI.image_compression.FAST:
				
				level = 3;
				filter_method = filterSub;
				break;
				
			case jsPDFAPI.image_compression.MEDIUM:
				
				level = 6;
				filter_method = filterAverage;
				break;
				
			case jsPDFAPI.image_compression.SLOW:
				
				level = 9;
				filter_method = filterPaeth;//uses to sum to choose best filter for each line
				break;
		}
		
		bytes = applyPngFilterMethod(bytes, lineLength, colorsPerPixel, filter_method);
		
		var header = new Uint8Array(createZlibHeader(level));
		var checksum = adler32(bytes);
		
		var deflate = new Deflater(level);
		var a = deflate.append(bytes);
		var cBytes = deflate.flush();
		
		var len = header.length + a.length + cBytes.length;
		
		var cmpd = new Uint8Array(len + 4);
		cmpd.set(header);
		cmpd.set(a, header.length);
		cmpd.set(cBytes, header.length + a.length);
		
		cmpd[len++] = (checksum >>> 24) & 0xff;
		cmpd[len++] = (checksum >>> 16) & 0xff;
		cmpd[len++] = (checksum >>> 8) & 0xff;
		cmpd[len++] = checksum & 0xff;
		
		return jsPDFAPI.arrayBufferToBinaryString(cmpd);
	}
	, createZlibHeader = function(bytes, level){
		/*
		 * @see http://www.ietf.org/rfc/rfc1950.txt for zlib header 
		 */
		var cm = 8;
        var cinfo = Math.LOG2E * Math.log(0x8000) - 8;
        var cmf = (cinfo << 4) | cm;
        
        var hdr = cmf << 8;
        var flevel = Math.min(3, ((level - 1) & 0xff) >> 1);
        
        hdr |= (flevel << 6);
        hdr |= 0;//FDICT
        hdr += 31 - (hdr % 31);
        
        return [cmf, (hdr & 0xff) & 0xff];
	}
	, adler32 = function(array, param) {
		var adler = 1;
	    var s1 = adler & 0xffff,
	        s2 = (adler >>> 16) & 0xffff;
	    var len = array.length;
	    var tlen;
	    var i = 0;

	    while (len > 0) {
	      tlen = len > param ? param : len;
	      len -= tlen;
	      do {
	        s1 += array[i++];
	        s2 += s1;
	      } while (--tlen);

	      s1 %= 65521;
	      s2 %= 65521;
	    }

	    return ((s2 << 16) | s1) >>> 0;
	}
	, applyPngFilterMethod = function(bytes, lineLength, colorsPerPixel, filter_method) {
		var lines = bytes.length / lineLength,
			result = new Uint8Array(bytes.length + lines),
			filter_methods = getFilterMethods(),
			i = 0, line, prevLine, offset;
		
		for(; i < lines; i++) {
			offset = i * lineLength;
			line = bytes.subarray(offset, offset + lineLength);
			
			if(filter_method) {
				result.set(filter_method(line, colorsPerPixel, prevLine), offset + i);
				
			}else{
			
				var j = 0,
					len = filter_methods.length,
					results = [];
				
				for(; j < len; j++)
					results[j] = filter_methods[j](line, colorsPerPixel, prevLine);
				
				var ind = getIndexOfSmallestSum(results.concat());
				
				result.set(results[ind], offset + i);
			}
			
			prevLine = line;
		}
		
		return result;
	}
	, filterNone = function(line, colorsPerPixel, prevLine) {
		/*var result = new Uint8Array(line.length + 1);
		result[0] = 0;
		result.set(line, 1);*/
		
		var result = Array.apply([], line);
		result.unshift(0);

		return result;
	}
	, filterSub = function(line, colorsPerPixel, prevLine) {
		var result = [],
			i = 0,
			len = line.length,
			left;
		
		result[0] = 1;
		
		for(; i < len; i++) {
			left = line[i - colorsPerPixel] || 0;
			result[i + 1] = (line[i] - left + 0x0100) & 0xff;
		}
		
		return result;
	}
	, filterUp = function(line, colorsPerPixel, prevLine) {
		var result = [],
			i = 0,
			len = line.length,
			up;
		
		result[0] = 2;
		
		for(; i < len; i++) {
			up = prevLine && prevLine[i] || 0;
			result[i + 1] = (line[i] - up + 0x0100) & 0xff;
		}
		
		return result;
	}
	, filterAverage = function(line, colorsPerPixel, prevLine) {
		var result = [],
			i = 0,
			len = line.length,
			left,
			up;
	
		result[0] = 3;
		
		for(; i < len; i++) {
			left = line[i - colorsPerPixel] || 0;
			up = prevLine && prevLine[i] || 0;
			result[i + 1] = (line[i] + 0x0100 - ((left + up) >>> 1)) & 0xff;
		}
		
		return result;
	}
	, filterPaeth = function(line, colorsPerPixel, prevLine) {
		var result = [],
			i = 0,
			len = line.length,
			left,
			up,
			upLeft,
			paeth;
		
		result[0] = 4;
		
		for(; i < len; i++) {
			left = line[i - colorsPerPixel] || 0;
			up = prevLine && prevLine[i] || 0;
			upLeft = prevLine && prevLine[i - colorsPerPixel] || 0;
			paeth = paethPredictor(left, up, upLeft);
			result[i + 1] = (line[i] - paeth + 0x0100) & 0xff;
		}
		
		return result;
	}
	,paethPredictor = function(left, up, upLeft) {

		var p = left + up - upLeft,
	        pLeft = Math.abs(p - left),
	        pUp = Math.abs(p - up),
	        pUpLeft = Math.abs(p - upLeft);
		
		return (pLeft <= pUp && pLeft <= pUpLeft) ? left : (pUp <= pUpLeft) ? up : upLeft;
	}
	, getFilterMethods = function() {
		return [filterNone, filterSub, filterUp, filterAverage, filterPaeth];
	}
	,getIndexOfSmallestSum = function(arrays) {
		var i = 0,
			len = arrays.length,
			sum, min, ind;
		
		while(i < len) {
			sum = absSum(arrays[i].slice(1));
			
			if(sum < min || !min) {
				min = sum;
				ind = i;
			}
			
			i++;
		}
		
		return ind;
	}
	, absSum = function(array) {
		var i = 0,
			len = array.length,
			sum = 0;
	
		while(i < len)
			sum += Math.abs(array[i++]);
			
		return sum;
	}
	, logImg = function(img) {
		console.log("width: " + img.width);
		console.log("height: " + img.height);
		console.log("bits: " + img.bits);
		console.log("colorType: " + img.colorType);
		console.log("transparency:");
		console.log(img.transparency);
		console.log("text:");
		console.log(img.text);
		console.log("compressionMethod: " + img.compressionMethod);
		console.log("filterMethod: " + img.filterMethod);
		console.log("interlaceMethod: " + img.interlaceMethod);
		console.log("imgData:");
		console.log(img.imgData);
		console.log("palette:");
		console.log(img.palette);
		console.log("colors: " + img.colors);
		console.log("colorSpace: " + img.colorSpace);
		console.log("pixelBitlength: " + img.pixelBitlength);
		console.log("hasAlphaChannel: " + img.hasAlphaChannel);
	};
	
	
	
	
	jsPDFAPI.processPNG = function(imageData, imageIndex, alias, compression, dataAsBinaryString) {
		'use strict'
		
		var colorSpace = this.color_spaces.DEVICE_RGB,
			decode = this.decode.FLATE_DECODE,
			bpc = 8,
			img, dp, trns,
			colors, pal, smask;
		
	/*	if(this.isString(imageData)) {
			
		}*/
		
		if(this.isArrayBuffer(imageData))
			imageData = new Uint8Array(imageData);
		
		if(this.isArrayBufferView(imageData)) {
			
			if(doesNotHavePngJS())
				throw new Error("PNG support requires png.js and zlib.js");
				
			img = new PNG(imageData);
			imageData = img.imgData;
			bpc = img.bits;
			colorSpace = img.colorSpace;
			colors = img.colors;
			
			//logImg(img);
			
			/*
			 * colorType 6 - Each pixel is an R,G,B triple, followed by an alpha sample.
			 * 
			 * colorType 4 - Each pixel is a grayscale sample, followed by an alpha sample.
			 * 
			 * Extract alpha to create two separate images, using the alpha as a sMask
			 */
			if([4,6].indexOf(img.colorType) !== -1) {
				
				/*
				 * processes 8 bit RGBA and grayscale + alpha images
				 */
				if(img.bits === 8) {
				
  				        var pixels = img.pixelBitlength == 32 ? new Uint32Array(img.decodePixels().buffer) : img.pixelBitlength == 16 ? new Uint16Array(img.decodePixels().buffer) : new Uint8Array(img.decodePixels().buffer),
						len = pixels.length,
						imgData = new Uint8Array(len * img.colors),
						alphaData = new Uint8Array(len),
						pDiff = img.pixelBitlength - img.bits,
						i = 0, n = 0, pixel, pbl;
				
					for(; i < len; i++) {
						pixel = pixels[i];
						pbl = 0;
						
						while(pbl < pDiff) {
							
							imgData[n++] = ( pixel >>> pbl ) & 0xff;
							pbl = pbl + img.bits;
						}
						
						alphaData[i] = ( pixel >>> pbl ) & 0xff;
					}
				}
				
				/*
				 * processes 16 bit RGBA and grayscale + alpha images
				 */
				if(img.bits === 16) {
					
					var pixels = new Uint32Array(img.decodePixels().buffer),
						len = pixels.length,
						imgData = new Uint8Array((len * (32 / img.pixelBitlength) ) * img.colors),
						alphaData = new Uint8Array(len * (32 / img.pixelBitlength) ),
						hasColors = img.colors > 1,
						i = 0, n = 0, a = 0, pixel;
					
					while(i < len) {
						pixel = pixels[i++];
						
						imgData[n++] = (pixel >>> 0) & 0xFF;
						
						if(hasColors) {
							imgData[n++] = (pixel >>> 16) & 0xFF;
							
							pixel = pixels[i++];
							imgData[n++] = (pixel >>> 0) & 0xFF;
						}
						
						alphaData[a++] = (pixel >>> 16) & 0xFF;
					}
					
					bpc = 8;
				}
				
				if(canCompress(compression)) {
										
					imageData = compressBytes(imgData, img.width * img.colors, img.colors, compression);
					smask = compressBytes(alphaData, img.width, 1, compression);
					
				}else{
					
					imageData = imgData;
					smask = alphaData;
					decode = null;
				}
			}
			
			/*
			 * Indexed png. Each pixel is a palette index.
			 */
			if(img.colorType === 3) {
				
				colorSpace = this.color_spaces.INDEXED;
				pal = img.palette;
				
				if(img.transparency.indexed) {
					
					var trans = img.transparency.indexed;
					
					var total = 0,
						i = 0,
						len = trans.length;

					for(; i<len; ++i)
					    total += trans[i];
					
					total = total / 255;
					
					/*
					 * a single color is specified as 100% transparent (0),
					 * so we set trns to use a /Mask with that index
					 */
					if(total === len - 1 && trans.indexOf(0) !== -1) {
						trns = [trans.indexOf(0)];
					
					/*
					 * there's more than one colour within the palette that specifies
					 * a transparency value less than 255, so we unroll the pixels to create an image sMask
					 */
					}else if(total !== len){
						
						var pixels = img.decodePixels(),
							alphaData = new Uint8Array(pixels.length),
							i = 0,
							len = pixels.length;
						
						for(; i < len; i++)
							alphaData[i] = trans[pixels[i]];
						
						smask = compressBytes(alphaData, img.width, 1);
					}
				}
			}
			
			if(decode === this.decode.FLATE_DECODE)
				dp = '/Predictor 15 /Colors '+ colors +' /BitsPerComponent '+ bpc +' /Columns '+ img.width;
			else
				//remove 'Predictor' as it applies to the type of png filter applied to its IDAT - we only apply with compression
				dp = '/Colors '+ colors +' /BitsPerComponent '+ bpc +' /Columns '+ img.width;
			
			if(this.isArrayBuffer(imageData) || this.isArrayBufferView(imageData))
				imageData = this.arrayBufferToBinaryString(imageData);
			
			if(smask && this.isArrayBuffer(smask) || this.isArrayBufferView(smask))
				smask = this.arrayBufferToBinaryString(smask);
			
			return this.createImageInfo(imageData, img.width, img.height, colorSpace,
										bpc, decode, imageIndex, alias, dp, trns, pal, smask);
		}
		
		throw new Error("Unsupported PNG image data, try using JPEG instead.");
	}

})(jsPDF.API)