if(!window.Color) Color = { };
if(!window.Color.Vision) Color.Vision = { };

(function() {

/* 
	Color.Vision.Simulate : v0.1
	-----------------------------
	Freely available for non-commercial use by Matthew Wickline and the
	Human-Computer Interaction Resource Network ( http://hcirn.com/ ).
	
	"Color-Defective Vision and Computer Graphics Displays" by Gary W. Meyer and Donald P. Greenberg
	http://ieeexplore.ieee.org/iel1/38/408/00007759.pdf?arnumber=7759
	
	"Spectral sensitivity of the foveal cone photopigments between 400 and 500 nm" by V.C. Smith, J. Pokorny
	http://www.opticsinfobase.org/abstract.cfm?URI=josaa-22-10-2060
	
	"RGB Working Space Information" by Bruce Lindbloom
	http://www.brucelindbloom.com/WorkingSpaceInfo.html
	
*/

var ConfusionLines = {
	"Protanope": {
		x: 0.7465,
		y: 0.2535,
		m: 1.273463,
		yint: -0.073894
	},
	"Deuteranope": {
		x: 1.4,
		y: -0.4,
		m: 0.968437,
		yint: 0.003331
	},
	"Tritanope": {
		x: 0.1748,
		y: 0.0,
		m: 0.062921,
		yint: 0.292119
	}
};

Color.Vision.Simulate = function(image, options) {
	if(!options) options = { };
	var type = typeof options.type == "string" ? options.type : "Normal", 
		amount = typeof options.amount == "number" ? options.amount : 1.0,
		canvas = document.createElement("canvas"),
		ctx = canvas.getContext("2d");
	canvas.width = image.width;
	canvas.height = image.height;
	ctx.drawImage(image, 0, 0);
	var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height),
		data = imageData.data;
	// Apply simulation
	switch(type) {
		case "Normal":
			document.body.appendChild(canvas);
			return;
		case "Achromatope":
			for(var id = 0, length = data.length; id < length; id += 4) {
				var sr = data[id], // source-pixel
					sg = data[id + 1],
					sb = data[id + 2],
					// convert to Monochrome using sRGB WhitePoint	
					dr = (sr * 0.212656 + sg * 0.715158 + sb * 0.072186), // destination-pixel
					dg = dr,
					db = dr;
				// Anomylize colors
				dr = sr * (1.0 - amount) + dr * amount; 
				dg = sg * (1.0 - amount) + dg * amount;
				db = sb * (1.0 - amount) + db * amount;
				// Record values
				data[id] = dr >> 0;
				data[id + 1] = dg >> 0;
				data[id + 2] = db >> 0;
			}
			// Record data
			ctx.putImageData(imageData, 0, 0);
			document.body.appendChild(canvas);
			return;
		case "Custom":
			var confuse_x = options.x,
				confuse_y = options.y, 
				confuse_m = options.m,
				confuse_yint = options.yint;
			break;
		default:
			var line = ConfusionLines[type],
				confuse_x = line.x,
				confuse_y = line.y, 
				confuse_m = line.m,
				confuse_yint = line.yint;
			break;
	}
	// Simulate: Protanope, Deuteranope, or Tritanope
	for(var id = 0, length = data.length; id < length; id += 4) {
		var sr = data[id], // source-pixel
			sg = data[id + 1],
			sb = data[id + 2],
			dr = sr, // destination-pixel
			dg = sg,
			db = sb;
		// Convert source color into XYZ color space
		var pow_r = Math.pow(sr, 2.2),
			pow_g = Math.pow(sg, 2.2),
			pow_b = Math.pow(sb, 2.2);
		var X = pow_r * 0.412424 + pow_g * 0.357579 + pow_b * 0.180464, // RGB->XYZ (sRGB:D65)
			Y = pow_r * 0.212656 + pow_g * 0.715158 + pow_b * 0.0721856,
			Z = pow_r * 0.0193324 + pow_g * 0.119193 + pow_b * 0.950444;
		// Convert XYZ into xyY Chromacity Coordinates (xy) and Luminance (Y)
		var chroma_x = X / (X + Y + Z);
		var chroma_y = Y / (X + Y + Z);
		// Generate the “Confusion Line" between the source color and the Confusion Point
		var m = (chroma_y - confuse_y) / (chroma_x - confuse_x); // slope of Confusion Line
		var yint = chroma_y - chroma_x * m; // y-intercept of confusion line (x-intercept = 0.0)
		// How far the xy coords deviate from the simulation
		var deviate_x = (confuse_yint - yint) / (m - confuse_m);
		var deviate_y = (m * deviate_x) + yint;
		// Compute the simulated color’s XYZ coords
		var X = deviate_x * Y / deviate_y;
		var Z = (1.0 - (deviate_x + deviate_y)) * Y / deviate_y;
		// Neutral grey calculated from luminance (in D65)
		var neutral_X = 0.312713 * Y / 0.329016; 
		var neutral_Z = 0.358271 * Y / 0.329016; 
		// Difference between simulated color and neutral grey
		var diff_X = neutral_X - X;
		var diff_Z = neutral_Z - Z;
		diff_r = diff_X * 3.24071 + diff_Z * -0.498571; // XYZ->RGB (sRGB:D65)
		diff_g = diff_X * -0.969258 + diff_Z * 0.0415557;
		diff_b = diff_X * 0.0556352 + diff_Z * 1.05707;
		// Convert to RGB color space
		dr = X * 3.24071 + Y * -1.53726 + Z * -0.498571; // XYZ->RGB (sRGB:D65)
		dg = X * -0.969258 + Y * 1.87599 + Z * 0.0415557;
		db = X * 0.0556352 + Y * -0.203996 + Z * 1.05707;
		// Compensate simulated color towards a neutral fit in RGB space
		var fit_r = ((dr < 0.0 ? 0.0 : 1.0) - dr) / diff_r;
		var fit_g = ((dg < 0.0 ? 0.0 : 1.0) - dg) / diff_g;
		var fit_b = ((db < 0.0 ? 0.0 : 1.0) - db) / diff_b;
		var adjust = Math.max( // highest value
			(fit_r > 1.0 || fit_r < 0.0) ? 0.0 : fit_r, 
			(fit_g > 1.0 || fit_g < 0.0) ? 0.0 : fit_g, 
			(fit_b > 1.0 || fit_b < 0.0) ? 0.0 : fit_b
		);
		// Shift proportional to the greatest shift
		dr = dr + (adjust * diff_r);
		dg = dg + (adjust * diff_g);
		db = db + (adjust * diff_b);
		// Apply gamma correction
		dr = Math.pow(dr, 1.0 / 2.2);
		dg = Math.pow(dg, 1.0 / 2.2);
		db = Math.pow(db, 1.0 / 2.2);
		// Anomylize colors
		dr = sr * (1.0 - amount) + dr * amount; 
		dg = sg * (1.0 - amount) + dg * amount;
		db = sb * (1.0 - amount) + db * amount;
		// Return values
		data[id] = dr >> 0;
		data[id + 1] = dg >> 0;
		data[id + 2] = db >> 0;
	}
	// Record data
	ctx.putImageData(imageData, 0, 0);
	if(typeof options.callback == "function") {
		options.callback(canvas);
	}
};

})();