StackBlur.js

var mul_table = [
        512,512,456,512,328,456,335,512,405,328,271,456,388,335,292,512,
        454,405,364,328,298,271,496,456,420,388,360,335,312,292,273,512,
        482,454,428,405,383,364,345,328,312,298,284,271,259,496,475,456,
        437,420,404,388,374,360,347,335,323,312,302,292,282,273,265,512,
        497,482,468,454,441,428,417,405,394,383,373,364,354,345,337,328,
        320,312,305,298,291,284,278,271,265,259,507,496,485,475,465,456,
        446,437,428,420,412,404,396,388,381,374,367,360,354,347,341,335,
        329,323,318,312,307,302,297,292,287,282,278,273,269,265,261,512,
        505,497,489,482,475,468,461,454,447,441,435,428,422,417,411,405,
        399,394,389,383,378,373,368,364,359,354,350,345,341,337,332,328,
        324,320,316,312,309,305,301,298,294,291,287,284,281,278,274,271,
        268,265,262,259,257,507,501,496,491,485,480,475,470,465,460,456,
        451,446,442,437,433,428,424,420,416,412,408,404,400,396,392,388,
        385,381,377,374,370,367,363,360,357,354,350,347,344,341,338,335,
        332,329,326,323,320,318,315,312,310,307,304,302,299,297,294,292,
        289,287,285,282,280,278,275,273,271,269,267,265,263,261,259];
        
   
var shg_table = [
	     9, 11, 12, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 
		17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19, 
		19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20,
		20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21,
		21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
		21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 
		22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
		22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23, 
		23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
		23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
		23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 
		23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 
		24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
		24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
		24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
		24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24 ];
 
function stackBlurImage( imageID, canvasID, radius,maindiv )
{
			
 	var img = document.getElementById( imageID );
	var canvas = document.getElementById( canvasID );
    var mainDiv = document.getElementById( maindiv );
    
	 var oMainH = $(mainDiv).height();
	 var oMainW = $(mainDiv).width();
	 var oMainL = $(mainDiv).offset().left;
	 var oMainT = $(mainDiv).offset().top;
 
	 canvas.style.width  = oMainW + "px";
	 canvas.style.height = oMainH + "px";
	 canvas.width = oMainW;
	 canvas.height = oMainH;
	 canvas.style.left = oMainL + "px";
	 canvas.style.top = oMainT + "px";
    
     var context = canvas.getContext("2d");
     context.clearRect( 0, 0, oMainW, oMainH );
 
	 context.drawImage( img,oMainL,oMainT,oMainW,oMainH, 0, 0 ,oMainW,oMainH );
		
 
	if ( isNaN(radius) || radius < 1 ) return;
	
	stackBlurCanvasRGBA( canvasID, 0, 0, oMainW, oMainH, radius );
	
}
 
 
function stackBlurCanvasRGBA( id, top_x, top_y, width, height, radius )
{
	if ( isNaN(radius) || radius < 1 ) return;
	radius |= 0;
	
	var canvas  = document.getElementById( id );
	var context = canvas.getContext("2d");
	var imageData;
	
	try {
	  try {
		imageData = context.getImageData( top_x, top_y, width, height );
	  } catch(e) {
	  
		// NOTE: this part is supposedly only needed if you want to work with local files
		// so it might be okay to remove the whole try/catch block and just use
		// imageData = context.getImageData( top_x, top_y, width, height );
		try {
			netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
			imageData = context.getImageData( top_x, top_y, width, height );
		} catch(e) {
			alert("Cannot access local image");
			throw new Error("unable to access local image data: " + e);
			return;
		}
	  }
	} catch(e) {
	  alert("Cannot access image");
	  throw new Error("unable to access image data: " + e);
	}
			
	var pixels = imageData.data;
			
	var x, y, i, p, yp, yi, yw, r_sum, g_sum, b_sum, a_sum, 
	r_out_sum, g_out_sum, b_out_sum, a_out_sum,
	r_in_sum, g_in_sum, b_in_sum, a_in_sum, 
	pr, pg, pb, pa, rbs;
			
	var div = radius + radius + 1;
	var w4 = width << 2;
	var widthMinus1  = width - 1;
	var heightMinus1 = height - 1;
	var radiusPlus1  = radius + 1;
	var sumFactor = radiusPlus1 * ( radiusPlus1 + 1 ) / 2;
	
	var stackStart = new BlurStack();
	var stack = stackStart;
	for ( i = 1; i < div; i++ )
	{
		stack = stack.next = new BlurStack();
		if ( i == radiusPlus1 ) var stackEnd = stack;
	}
	stack.next = stackStart;
	var stackIn = null;
	var stackOut = null;
	
	yw = yi = 0;
	
	var mul_sum = mul_table[radius];
	var shg_sum = shg_table[radius];
	
	for ( y = 0; y < height; y++ )
	{
		r_in_sum = g_in_sum = b_in_sum = a_in_sum = r_sum = g_sum = b_sum = a_sum = 0;
		
		r_out_sum = radiusPlus1 * ( pr = pixels[yi] );
		g_out_sum = radiusPlus1 * ( pg = pixels[yi+1] );
		b_out_sum = radiusPlus1 * ( pb = pixels[yi+2] );
		a_out_sum = radiusPlus1 * ( pa = pixels[yi+3] );
		
		r_sum += sumFactor * pr;
		g_sum += sumFactor * pg;
		b_sum += sumFactor * pb;
		a_sum += sumFactor * pa;
		
		stack = stackStart;
		
		for( i = 0; i < radiusPlus1; i++ )
		{
			stack.r = pr;
			stack.g = pg;
			stack.b = pb;
			stack.a = pa;
			stack = stack.next;
		}
		
		for( i = 1; i < radiusPlus1; i++ )
		{
			p = yi + (( widthMinus1 < i ? widthMinus1 : i ) << 2 );
			r_sum += ( stack.r = ( pr = pixels[p])) * ( rbs = radiusPlus1 - i );
			g_sum += ( stack.g = ( pg = pixels[p+1])) * rbs;
			b_sum += ( stack.b = ( pb = pixels[p+2])) * rbs;
			a_sum += ( stack.a = ( pa = pixels[p+3])) * rbs;
			
			r_in_sum += pr;
			g_in_sum += pg;
			b_in_sum += pb;
			a_in_sum += pa;
			
			stack = stack.next;
		}
		
		
		stackIn = stackStart;
		stackOut = stackEnd;
		for ( x = 0; x < width; x++ )
		{
			pixels[yi+3] = pa = (a_sum * mul_sum) >> shg_sum;
			if ( pa != 0 )
			{
				pa = 255 / pa;
				pixels[yi]   = ((r_sum * mul_sum) >> shg_sum) * pa;
				pixels[yi+1] = ((g_sum * mul_sum) >> shg_sum) * pa;
				pixels[yi+2] = ((b_sum * mul_sum) >> shg_sum) * pa;
			} else {
				pixels[yi] = pixels[yi+1] = pixels[yi+2] = 0;
			}
			
			r_sum -= r_out_sum;
			g_sum -= g_out_sum;
			b_sum -= b_out_sum;
			a_sum -= a_out_sum;
			
			r_out_sum -= stackIn.r;
			g_out_sum -= stackIn.g;
			b_out_sum -= stackIn.b;
			a_out_sum -= stackIn.a;
			
			p =  ( yw + ( ( p = x + radius + 1 ) < widthMinus1 ? p : widthMinus1 ) ) << 2;
			
			r_in_sum += ( stackIn.r = pixels[p]);
			g_in_sum += ( stackIn.g = pixels[p+1]);
			b_in_sum += ( stackIn.b = pixels[p+2]);
			a_in_sum += ( stackIn.a = pixels[p+3]);
			
			r_sum += r_in_sum;
			g_sum += g_in_sum;
			b_sum += b_in_sum;
			a_sum += a_in_sum;
			
			stackIn = stackIn.next;
			
			r_out_sum += ( pr = stackOut.r );
			g_out_sum += ( pg = stackOut.g );
			b_out_sum += ( pb = stackOut.b );
			a_out_sum += ( pa = stackOut.a );
			
			r_in_sum -= pr;
			g_in_sum -= pg;
			b_in_sum -= pb;
			a_in_sum -= pa;
			
			stackOut = stackOut.next;
 
			yi += 4;
		}
		yw += width;
	}
 
	
	for ( x = 0; x < width; x++ )
	{
		g_in_sum = b_in_sum = a_in_sum = r_in_sum = g_sum = b_sum = a_sum = r_sum = 0;
		
		yi = x << 2;
		r_out_sum = radiusPlus1 * ( pr = pixels[yi]);
		g_out_sum = radiusPlus1 * ( pg = pixels[yi+1]);
		b_out_sum = radiusPlus1 * ( pb = pixels[yi+2]);
		a_out_sum = radiusPlus1 * ( pa = pixels[yi+3]);
		
		r_sum += sumFactor * pr;
		g_sum += sumFactor * pg;
		b_sum += sumFactor * pb;
		a_sum += sumFactor * pa;
		
		stack = stackStart;
		
		for( i = 0; i < radiusPlus1; i++ )
		{
			stack.r = pr;
			stack.g = pg;
			stack.b = pb;
			stack.a = pa;
			stack = stack.next;
		}
		
		yp = width;
		
		for( i = 1; i <= radius; i++ )
		{
			yi = ( yp + x ) << 2;
			
			r_sum += ( stack.r = ( pr = pixels[yi])) * ( rbs = radiusPlus1 - i );
			g_sum += ( stack.g = ( pg = pixels[yi+1])) * rbs;
			b_sum += ( stack.b = ( pb = pixels[yi+2])) * rbs;
			a_sum += ( stack.a = ( pa = pixels[yi+3])) * rbs;
		   
			r_in_sum += pr;
			g_in_sum += pg;
			b_in_sum += pb;
			a_in_sum += pa;
			
			stack = stack.next;
		
			if( i < heightMinus1 )
			{
				yp += width;
			}
		}
		
		yi = x;
		stackIn = stackStart;
		stackOut = stackEnd;
		for ( y = 0; y < height; y++ )
		{
			p = yi << 2;
			pixels[p+3] = pa = (a_sum * mul_sum) >> shg_sum;
			if ( pa > 0 )
			{
				pa = 255 / pa;
				pixels[p]   = ((r_sum * mul_sum) >> shg_sum ) * pa;
				pixels[p+1] = ((g_sum * mul_sum) >> shg_sum ) * pa;
				pixels[p+2] = ((b_sum * mul_sum) >> shg_sum ) * pa;
			} else {
				pixels[p] = pixels[p+1] = pixels[p+2] = 0;
			}
			
			r_sum -= r_out_sum;
			g_sum -= g_out_sum;
			b_sum -= b_out_sum;
			a_sum -= a_out_sum;
		   
			r_out_sum -= stackIn.r;
			g_out_sum -= stackIn.g;
			b_out_sum -= stackIn.b;
			a_out_sum -= stackIn.a;
			
			p = ( x + (( ( p = y + radiusPlus1) < heightMinus1 ? p : heightMinus1 ) * width )) << 2;
			
			r_sum += ( r_in_sum += ( stackIn.r = pixels[p]));
			g_sum += ( g_in_sum += ( stackIn.g = pixels[p+1]));
			b_sum += ( b_in_sum += ( stackIn.b = pixels[p+2]));
			a_sum += ( a_in_sum += ( stackIn.a = pixels[p+3]));
		   
			stackIn = stackIn.next;
			
			r_out_sum += ( pr = stackOut.r );
			g_out_sum += ( pg = stackOut.g );
			b_out_sum += ( pb = stackOut.b );
			a_out_sum += ( pa = stackOut.a );
			
			r_in_sum -= pr;
			g_in_sum -= pg;
			b_in_sum -= pb;
			a_in_sum -= pa;
			
			stackOut = stackOut.next;
			
			yi += width;
		}
	}
	
	context.putImageData( imageData, top_x, top_y );
	
}
 
function BlurStack()
{
	this.r = 0;
	this.g = 0;
	this.b = 0;
	this.a = 0;
	this.next = null;
}