/*

StackBlur - a fast almost Gaussian Blur For Canvas

Version: 	0.5
Author:		Mario Klingemann
Contact: 	mario@quasimondo.com
Website:	http://www.quasimondo.com/StackBlurForCanvas
Twitter:	@quasimondo

In case you find this class useful - especially in commercial projects -
I am not totally unhappy for a small donation to my PayPal account
mario@quasimondo.de

Or support me on flattr:
https://flattr.com/thing/72791/StackBlur-a-fast-almost-Gaussian-Blur-Effect-for-CanvasJavascript

Copyright (c) 2010 Mario Klingemann

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.
*/

const 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];


const 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, blurAlphaChannel) {

 	const img = document.getElementById(imageID);
	const w = img.naturalWidth;
	const h = img.naturalHeight;

	const canvas = document.getElementById(canvasID);

	canvas.style.width  = w + "px";
	canvas.style.height = h + "px";
	canvas.width = w;
	canvas.height = h;

	const context = canvas.getContext("2d");

	context.clearRect(0, 0, w, h);
	context.drawImage(img, 0, 0);

	if (isNaN(radius) || radius < 1) return;

	if (blurAlphaChannel)
		stackBlurCanvasRGBA(canvasID, 0, 0, w, h, radius);
	else
		stackBlurCanvasRGB(canvasID, 0, 0, w, h, radius);
}


function stackBlurCanvasRGBA(id, top_x, top_y, width, height, radius) {
	if (isNaN(radius) || radius < 1) return;

	radius |= 0;

	const canvas  = document.getElementById(id);
	const context = canvas.getContext("2d");
	let 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);
	}

	const pixels = imageData.data;

	let x; let y; let i; let p; let yp; let yi; let yw; let r_sum; let g_sum; let b_sum; let a_sum;
	let r_out_sum; let g_out_sum; let b_out_sum; let a_out_sum;
	let r_in_sum; let g_in_sum; let b_in_sum; let a_in_sum;
	let pr; let pg; let pb; let pa; let rbs;

	const div = radius + radius + 1;
	const w4 = width << 2;
	const widthMinus1  = width - 1;
	const heightMinus1 = height - 1;
	const radiusPlus1  = radius + 1;
	const sumFactor = radiusPlus1 * (radiusPlus1 + 1) / 2;

	const stackStart = new BlurStack();
	let stack = stackStart;

	for (i = 1; i < div; i++) {
		stack = stack.next = new BlurStack();

		if (i === radiusPlus1) var stackEnd = stack;
	}
	stack.next = stackStart;
	let stackIn = null;
	let stackOut = null;

	yw = yi = 0;

	const mul_sum = mul_table[radius];
	const 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 stackBlurCanvasRGB(id, top_x, top_y, width, height, radius) {
	if (isNaN(radius) || radius < 1) return;

	radius |= 0;

	const canvas  = document.getElementById(id);
	const context = canvas.getContext("2d");
	let 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);
	}

	const pixels = imageData.data;

	let x; let y; let i; let p; let yp; let yi; let yw; let r_sum; let g_sum; let b_sum;
	let r_out_sum; let g_out_sum; let b_out_sum;
	let r_in_sum; let g_in_sum; let b_in_sum;
	let pr; let pg; let pb; let rbs;

	const div = radius + radius + 1;
	const w4 = width << 2;
	const widthMinus1  = width - 1;
	const heightMinus1 = height - 1;
	const radiusPlus1  = radius + 1;
	const sumFactor = radiusPlus1 * (radiusPlus1 + 1) / 2;

	const stackStart = new BlurStack();
	let stack = stackStart;

	for (i = 1; i < div; i++) {
		stack = stack.next = new BlurStack();

		if (i == radiusPlus1) var stackEnd = stack;
	}
	stack.next = stackStart;
	let stackIn = null;
	let stackOut = null;

	yw = yi = 0;

	const mul_sum = mul_table[radius];
	const shg_sum = shg_table[radius];

	for (y = 0; y < height; y++) {
		r_in_sum = g_in_sum = b_in_sum = r_sum = g_sum = b_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]);

		r_sum += sumFactor * pr;
		g_sum += sumFactor * pg;
		b_sum += sumFactor * pb;

		stack = stackStart;

		for (i = 0; i < radiusPlus1; i++) {
			stack.r = pr;
			stack.g = pg;
			stack.b = pb;
			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;

			r_in_sum += pr;
			g_in_sum += pg;
			b_in_sum += pb;

			stack = stack.next;
		}


		stackIn = stackStart;
		stackOut = stackEnd;
		for (x = 0; x < width; x++) {
			pixels[yi]   = (r_sum * mul_sum) >> shg_sum;
			pixels[yi+1] = (g_sum * mul_sum) >> shg_sum;
			pixels[yi+2] = (b_sum * mul_sum) >> shg_sum;

			r_sum -= r_out_sum;
			g_sum -= g_out_sum;
			b_sum -= b_out_sum;

			r_out_sum -= stackIn.r;
			g_out_sum -= stackIn.g;
			b_out_sum -= stackIn.b;

			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]);

			r_sum += r_in_sum;
			g_sum += g_in_sum;
			b_sum += b_in_sum;

			stackIn = stackIn.next;

			r_out_sum += (pr = stackOut.r);
			g_out_sum += (pg = stackOut.g);
			b_out_sum += (pb = stackOut.b);

			r_in_sum -= pr;
			g_in_sum -= pg;
			b_in_sum -= pb;

			stackOut = stackOut.next;

			yi += 4;
		}
		yw += width;
	}


	for (x = 0; x < width; x++) {
		g_in_sum = b_in_sum = r_in_sum = g_sum = b_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]);

		r_sum += sumFactor * pr;
		g_sum += sumFactor * pg;
		b_sum += sumFactor * pb;

		stack = stackStart;

		for (i = 0; i < radiusPlus1; i++) {
			stack.r = pr;
			stack.g = pg;
			stack.b = pb;
			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;

			r_in_sum += pr;
			g_in_sum += pg;
			b_in_sum += pb;

			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]   = (r_sum * mul_sum) >> shg_sum;
			pixels[p+1] = (g_sum * mul_sum) >> shg_sum;
			pixels[p+2] = (b_sum * mul_sum) >> shg_sum;

			r_sum -= r_out_sum;
			g_sum -= g_out_sum;
			b_sum -= b_out_sum;

			r_out_sum -= stackIn.r;
			g_out_sum -= stackIn.g;
			b_out_sum -= stackIn.b;

			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]));

			stackIn = stackIn.next;

			r_out_sum += (pr = stackOut.r);
			g_out_sum += (pg = stackOut.g);
			b_out_sum += (pb = stackOut.b);

			r_in_sum -= pr;
			g_in_sum -= pg;
			b_in_sum -= pb;

			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;
}