LESS data-URI png generator

//Painting
.underline(@height: 20px, @color: @black){
  @pattern: "0000000000000000000000000000000000000001";
	.png(@stream: @pattern, @w: 1, @h: unit(@height), @color: @color);
}

.underline{
	.underline(@color: fade(@black, 10%));
	background-position: 0 -2px;
	&:hover{
		.underline(@color: @black);
	};
}


//Mixin that generates PNG to background
.png(@stream: "0001", @w: 2, @h: 2, @color: black){

	@r: red(@color);
	@g: green(@color);
	@b: blue(@color);
	@hexColor: rgb(red(@color),green(@color),blue(@color));
	@PLTE: `"ffffff" + ("@{hexColor}").substr(1)`; //Make bytes palette: first-white, rest-passed color;

	@a: alpha(@color);
	@tRNS: `"ff" + (function(){ var a = Math.round(@{a} * 255).toString(16); return (a.length == 1 ? "0" + a : a) })()`;

	//png.js: https://github.com/dfcreative/graphics/blob/master/src/PNG.js
	@initPNG: `(function(){
		Number.prototype.toUInt=function(){ return this<0?this+4294967296:this; };
		Number.prototype.bytes32=function(){ return [(this>>>24)&0xff,(this>>>16)&0xff,(this>>>8)&0xff,this&0xff]; };
		Number.prototype.bytes16sw=function(){ return [this&0xff,(this>>>8)&0xff]; };

		Array.prototype.adler32=function(start,len){
				switch(arguments.length){ 
					case 0:start=0; 
					case 1:len=this.length-start; 
				}
				var a=1,b=0;
				for(var i=0;i<len;i++){
					a = (a+this[start+i])%65521; b = (b+a)%65521;
				}
				return ((b << 16) | a).toUInt();
		};

		Array.prototype.crc32=function(start,len){
			switch(arguments.length){ case 0:start=0; case 1:len=this.length-start; }
			var table=arguments.callee.crctable;
			if(!table){
				table=[];
				var c;
				for (var n = 0; n < 256; n++) {
					c = n;
					for (var k = 0; k < 8; k++)
							c = c & 1?0xedb88320 ^ (c >>> 1):c >>> 1;
					table[n] = c.toUInt();
				}
				arguments.callee.crctable=table;
			}
			var c = 0xffffffff;
			for (var i = 0; i < len; i++)
				c = table[(c ^ this[start+i]) & 0xff] ^ (c>>>8);

			return (c^0xffffffff).toUInt();
		};

		String.prototype.toByteStream=function(){
			var s = []
			if (this.length%2 == 1) this = this + "0"
			for (var i = 0; i < this.length; i+=2){
				s.push(parseInt(this[i] + this[i+1], 16)&0xff);
			}
			return s;
		}

		//Class
		var PNG = function(opts){
			this.options = {};
			import$(this.options, PNG.defaults);
			import$(this.options, opts);
			import$(this, {
				data: null, //bitmap data stream
				chunks: null,
				width: 5,
				height: 5
			});
		}

		import$(PNG, {
			defaults: {		
				bitDepth: 0x08,
				colorType: 0x03, //3 - Indexed, 6 — trueColor with alpha
				compressMethod: 0x00, 
				filterMethod: 0x00, //0 - No filtering
				interlaceMethod: 0x00
			}
		});

		import$(PNG.prototype, {
			raw: function(){
				arguments.length ? this.setRaw.apply(this, arguments) : this.getRaw.apply(this, arguments);
			},

			getRaw: function(){
				return this.getStream().map(function(c){ c = c||0; return (c<15?"0"+c.toString(16): c.toString(16)); }).join('')
			},

			getStream: function(){		
				var self = this, o = self.options;

				//IHDR
				var s = [
					0x89,0x50,0x4e,0x47,0x0d,0x0a,0x1a,0x0a, //BOF
					0x00,0x00,0x00,0x0d,0x49,0x48,0x44,0x52 //Length, IHDR
				];
				s = s.concat((+self.width).bytes32(), (+self.height).bytes32());
				s = s.concat(o.bitDepth, o.colorType, o.compressMethod, o.filterMethod, o.interlaceMethod);
				s = s.concat(s.crc32(12,17).bytes32());

				//PLTE
				if (o.colorType == 0x03) {
					var plteStream = self.chunks.PLTE.toByteStream();
					s = s.concat(plteStream.length.bytes32());
					var crcStart = s.length;
					s = s.concat(0x50, 0x4c, 0x54, 0x45); //PLTE
					s = s.concat(plteStream);
					s = s.concat(s.crc32(crcStart, plteStream.length + 4).bytes32());
				}

				//tRNS
				if (o.colorType == 0x03) {			
					var trnsStream = self.chunks.tRNS.toByteStream();
					s = s.concat(trnsStream.length.bytes32());
					var crcStart = s.length;
					s = s.concat(0x74, 0x52, 0x4e, 0x53); //tRNS
					s = s.concat(trnsStream);
					s = s.concat(s.crc32(crcStart, trnsStream.length + 4).bytes32());
				} else {
					//IDAT stream 
				}

				//IDAT
				var dataStream = self.data.toByteStream();
				var w = self.width, h = self.height,
					l = (o.colorType == 0x03 ? 1 : 4); //How much bytes per pixel //TODO: check other than 8bit color

				var len=h*(w*l+1); //+1 is filter type (00)
				for(var y=0;y<h;y++)
					dataStream.splice(y*(w*l+1),0,0x00); //insert filter type (0x00) before the each scanline (row)

				var blocks=Math.ceil(len/32768); //32768 - max block length?

				s = s.concat( (len+ 5*blocks +6).bytes32() ); //length = dataLen + (btype+ lenx2 + nlenx2) + zlib_header + adler
				s = s.concat(0x49, 0x44, 0x41, 0x54); //IDAT

				var crcStart=s.length;
				var crcLen=(len+5*blocks+6+4); //datalen + header

				//zlib
				//http://www.w3.org/TR/2003/REC-PNG-20031110/#10CompressionCM0
				//http://tools.ietf.org/html/rfc1950#page-4	
				s = s.concat(0x78, 0x01) //7 - 2^7, 8 - deflate method, 01 - fastest compression, no dict, checkflag
				//s = s.concat(0x01, (0x02).bytes16sw(), (~0x02).bytes16sw(), dataStream) //01 - end-block header, len, nlen, rawdata
						
				for(var i=0;i<blocks;i++){
					var blockLen=Math.min(32768,len-(i*32768)); //last block length detection
					s.push(i==(blocks-1)?0x01:0x00); //end block or not
					s = s.concat(blockLen.bytes16sw() ); //blocklen
					s = s.concat((~blockLen).bytes16sw() ); //blocklencomplement
					var id=dataStream.slice(i*32768,i*32768+blockLen); //splice part of image data
					s = s.concat( id ); //write it raw
				}

				s = s.concat( dataStream.adler32().bytes32() ); //make adler
				s = s.concat( s.crc32(crcStart, crcLen).bytes32() );


				//IEND
				s = s.concat(0x00,0x00,0x00,0x00,0x49,0x45,0x4e,0x44);//Length, IEND
				s = s.concat(s.crc32(s.length-4, 4).bytes32());
				return s;
			},

			set: function(settings){
				import$(this, settings);
			},

			toDataURL: function(){
				var self = this, o = self.options;
				var dataURI = "data:image/png;base64,"+ btoa( self.getStream().map(function(c){ return String.fromCharCode(c); }).join('') );
				return dataURI;
			}
		});

		//js crutches
		function import$(a, b){
			for (var key in b){
				a[key] = b[key];
			}
			return a;
		}
		
		var global = (1,eval)('this');
		global.PNG = PNG;

		return true;
	})()`;

	@background: `(function(){
		var png = new PNG();
		
		png.set({
			width: @{w},
			height: @{h},
			chunks:{
				PLTE: @{PLTE},
				tRNS: @{tRNS}
			},
			data: @{stream}
		})

		return "url(" + png.toDataURL() + ")";
	})()`;

	background-image: ~"@{background}";
}

.png{
	.png();
}