/**
 * pngdecode.js - 非圧縮png画像を読み込む
 *
 * 依存するライブラリ：なし
 * 影響を受けるプロパティ：なし
 */
function(data) {
	var create_stream = function(array) {
		if (!array) array = new Array();
		array.mark = 0;
		array.crc = 0xffffffff;
		array.crctable = [];
		for(var i = 0; i < 256; i++) {  
			var u = i>>>0;  
			for(var j = 0; j < 8; j++) {  
				if(u & 0x1) u = ((u >>> 1) ^ 0xEDB88320)>>>0;
				else        u >>>= 1;  
			}  
			array.crctable[i] = u>>>0;
		}

		array.append = function(obj) {
			if (typeof obj == 'object' && typeof obj.length == 'number') {
				for (var i = 0; i < obj.length; i++)
					this.push(obj[i]);
			} else {
				this.push(obj);
			}
		};
		array.read = function(len) {
			if (typeof len != 'number') len = 1;
			if (this.mark >= this.length)
				throw new Error("no more data");
			if (len == 1) {
				this.crc = ((this.crc >>> 8) ^ this.crctable[(this[this.mark] ^ this.crc) & 0xFF])>>>0;
				return this[this.mark++];
			} else {
				result = [];
				for (var i = 0; i < len; i++) result.push(this.read());
				return result;
			}
		};
		array.readShort = function() {
			return ((this.read()<<8) +
				(this.read()));
		};
		array.readInt = function() {
			return ((this.read()<<24) +
				(this.read()<<16) +
				(this.read()<<8) +
				(this.read()))>>>0;
		};
		array.readString = function(len) {
			var str = '';
			for (var i = 0; i < len; i++) {
				str += String.fromCharCode(this.read());
			}
			return str;
		};
		array.readZipShort = function() {
			return ((this.read()) +
				(this.read()<<8));
		};
		array.hasMore = function() {
			if (this.mark >= this.length) return false;
			else return true;
		};
		return array;
	};

	function defilter(width, height, bpp, literal) {
		var linesize = width * bpp + 1;
		for (var y = 0; y < height; y++) {
			var offset = y * linesize;
			switch(literal[offset]) { //filter type
			case 0: //None
				break;
			case 1: //Sub
				for (var x = 1; x <= width * bpp; x++) {
					var left = x < bpp + 1 ? 0 : literal[offset + x - bpp];
					literal[offset + x] = (literal[offset + x] + left) & 0xff;
				}
				break;
			case 2: //Up
				for (var x = 1; x <= width * bpp; x++) {
					var above = y <= 0 ? 0 : literal[offset - linesize + x];
					literal[offset + x] = (literal[offset + x] + above) & 0xff;
				}
				break;
			case 3: //Average
				for (var x = 1; x <= width * bpp; x++) {
					var left = x < bpp + 1 ? 0 : literal[offset + x - bpp];
					var above = y <= 0 ? 0 : literal[offset - linesize + x];
					literal[offset + x] = (literal[offset + x] + Math.floor((left + above)/2)) & 0xff;
				}
				break;
			case 4:
				for (var x = 1; x <= width * bpp; x++) {
					var left = x < bpp + 1 ? 0 : literal[offset + x - bpp];
					var above = y <= 0 ? 0 : literal[offset - linesize + x];
					var upleft = y <= 0 ? 0 : (x < bpp + 1 ? 0 : literal[offset - linesize + x - bpp]);
					literal[offset + x] = (literal[offset + x] + (function(a, b, c) {
						var p = (a + b - c);
						var pa = Math.abs(p - a);
						var pb = Math.abs(p - b);
						var pc = Math.abs(p - c);
						if (pa <= pb && pa <= pc) return a;
						else if (pb <= pc) return b;
						else return c;
					})(left, above, upleft)) & 0xff;
				}
				break;
			}
		}
	};

	function rgba(width, height, bpp, color, literal) {
		var bytes = [];
		var linesize = width * bpp + 1;
		for (var y = 0; y < height; y++) {
			var offset = y * linesize;
			for (var x = 1; x <= width*bpp; x += bpp) {
				var rgba = 0;
				switch(color) {
				case 0:
					rgba = 0xff000000 +
						(literal[offset + x]<<16) +
						(literal[offset + x]<<8) +
						(literal[offset + x]);
					break;
				case 2:
					rgba = 0xff000000 +
						(literal[offset + x]<<16) +
						(literal[offset + x + 1]<<8) +
						(literal[offset + x + 2]);
					break;
				case 3:
					rgb = 0xff000000 + literal[offset + x]; //PLTE
					break;
				case 4:
					rgba = (literal[offset + x + 1]<<24) +
						(literal[offset + x]<<16) +
						(literal[offset + x]<<8) +
						literal[offset + x];
					break;
				case 6:
					rgba = (literal[offset + x + 3]<<24) +
						(literal[offset + x]<<16) +
						(literal[offset + x + 1]<<8) +
						literal[offset + x + 2];
					break;
				}
				bytes.push(rgba>>>0);
			}
		}
		return bytes;
	};

	function decodeB64(data) {
		var stream = create_stream();
		var seed = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
		data.replace(/\s+/, '')
			.replace(/[a-zA-Z0-9\+\/]{1,4}/g, function(match) {
			var c = 0;
			for (var i = 0; i < match.length; i++) {
				c = (c << 6) + (seed.indexOf(match.substr(i,1)) & 0x3f);
			}
			switch(match.length) {
			case 4: stream.push((c>>16)&0xff);
				stream.push((c>>8)&0xff);
				stream.push(c&0xff);
				break;
			case 3:
				stream.push((c>>8)&0xff);
				stream.push(c&0xff);
				break;
			case 2:
				stream.push((c>>4)&0xff);
			}
		});
		return stream;
	};

	/**
	 * Load png image data by BASE64 encoded string or array.
	 */
	this.load = function(data) {
		var pngstream;
		if (typeof data == 'string') pngstream = decodeB64(data);
		else pngstream = create_stream(data);

		//read header
		var header = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
		for (var i = 0; i < header.length; i++) {
			var b = pngstream.read();
			if (b != header[i])
				throw new Error("bad header");
		}
	
		//read CHUNK
		var chunks = {};
		var width = 0, height = 0, color = 0, bpp = 0;

		while (pngstream.hasMore()) {
			var chunk = {};
			chunk.size = pngstream.readInt();
			pngstream.crc = 0xffffffff; //reset crc
			chunk.type = pngstream.readString(4);
			chunk.data = {};
			var stream = create_stream();
			for (var i = 0; i < chunk.size; i++)
				stream.push(pngstream.read());
			var crc = pngstream.crc;
			chunk.crc  = pngstream.readInt() >>> 0;
			/*
			if (crc != chunk.crc)
				console.log("bad crc:" +
					('00000000' + pngstream.crc.toString(16)).substr(-8,8) +
					"<=>" +
					('00000000' + chunk.crc.toString(16)).substr(-8,8));
			*/
			switch(chunk.type) {
			case 'IHDR':
				chunk.data.width = width = stream.readInt();
				chunk.data.height = height = stream.readInt();
				chunk.data.depth = stream.read();
				chunk.data.color = color = stream.read();
				chunk.data.compress = stream.read();
				chunk.data.filter = stream.read();
				chunk.data.interlace = stream.read();
				chunks[chunk.type] = chunk;
				break;

			case 'IDAT':
				if (!chunks['IDAT']) {
					chunk.data = stream;
					chunks['IDAT'] = chunk;
				} else {
					chunks['IDAT'].data.append(stream);
				}
				break;

			default:
				chunk.data = stream;
				chunks[chunk.type] = chunk;
			}
			//console.log(chunk);
		}
	
		//read deflated data
		//http://www.aya.or.jp/~sanami/peace/memorial/code21-30.html
		var chunk = chunks['IDAT'];
		var stream = chunk.data;
		var b = stream.read();
		chunk.data.CINFO = (b>>4)&0x0f;
		chunk.data.CM = b&0x0f;
		b = stream.read();
		chunk.data.FLEVEL = (b>>6)&0x03;
		chunk.data.FDICT  = (b>>5)&0x01;
		chunk.data.FCHECK = b&0x1f;

		b = stream.read();
		chunk.data.BTYPE = (b>>1)&0x03;
		if (chunk.data.BTYPE != 0)
			throw new Error('Unsupported compression ' + chunk.data.BTYPE + '!');
		chunk.data.BFINAL = b&0x01;
		chunk.data.LEN = stream.readZipShort();
		chunk.data.NLEN = stream.readZipShort();
		switch(color) {
		case 0: bpp = 1; break;
		case 2: bpp = 3; break;
		case 3: bpp = 1; break; //PLTE
		case 4: bpp = 2; break;
		case 6: bpp = 4; break;
		}

		chunk.data.LITERAL = stream.read(chunk.data.LEN);
		chunk.data.ADLER32 = stream.readInt();

		//defilter
		defilter(width, height, bpp, chunk.data.LITERAL);

		//rgba
		chunks['IDAT'].data.IMAGE = rgba(width, height, bpp, color, chunk.data.LITERAL);

		return this.img = {
			width  : chunks['IHDR'].data.width,
			height : chunks['IHDR'].data.height,
			data   : chunks['IDAT'].data.IMAGE
		};
	};

	/**
	 * Create rendered image DOM document.
	 */
	this.toDOM = function(scale) {
		if (typeof scale != 'number') scale = 1;
		var dot = function(x, y, color) {
			var p = canvas.appendChild(document.createElement('div'));
			p.style.position = 'absolute';
			p.style.overflow = 'hidden';
			p.style.width = scale + 'px';
			p.style.height = scale + 'px';
			p.style.left = (scale * x) + 'px';
			p.style.top = (scale * y) + 'px';
			var hex = ('000000' + (color&0xffffff).toString(16));
			hex = hex.substr(hex.length - 6, 6);
			p.style.backgroundColor = '#' + hex;
			var opacity = (color>>>24)/0xff;
			p.style.opacity = opacity;
			p.style.filter = 'alpha(opacity=' + (opacity*100) + ')';
		}
		var canvas = document.createElement('div');
		canvas.className = canvas.styleClass = 'png-image';
		canvas.style.overflow = 'hidden';
		canvas.style.width = (scale * this.img.width) + 'px';
		canvas.style.height = (scale * this.img.height) + 'px';
		canvas.style.position = 'relative';
		canvas.style.cssFloat = canvas.style.styleFloat = 'left';
		for (var y = 0; y < this.img.height; y++) {
			for (var x = 0; x < this.img.width; x++) {
				dot(x, y, this.img.data[this.img.width * y + x]);
			}
		}
		return canvas;
	};

	if (data) this.load(data);
}