webgl-image-filter.js

/* 
WebGLImageFilter - MIT Licensed

2013, Dominic Szablewski - phoboslab.org
*/

(function(window){

var WebGLProgram = function( gl, vertexSource, fragmentSource ) {

	var _collect = function( source, prefix, collection ) {
		var r = new RegExp('\\b' + prefix + ' \\w+ (\\w+)', 'ig');
		source.replace(r, function(match, name) {
			collection[name] = 0;
			return match;
		});
	};

	var _compile = function( gl, source, type ) {
		var shader = gl.createShader(type);
		gl.shaderSource(shader, source);
		gl.compileShader(shader);

		if( !gl.getShaderParameter(shader, gl.COMPILE_STATUS) ) {
			console.log(gl.getShaderInfoLog(shader));
			return null;
		}
		return shader;
	};


	this.uniform = {};
	this.attribute = {};

	var _vsh = _compile(gl, vertexSource, gl.VERTEX_SHADER);
	var _fsh = _compile(gl, fragmentSource, gl.FRAGMENT_SHADER);

	this.id = gl.createProgram();
	gl.attachShader(this.id, _vsh);
	gl.attachShader(this.id, _fsh);
	gl.linkProgram(this.id);

	if( !gl.getProgramParameter(this.id, gl.LINK_STATUS) ) {
		console.log(gl.getProgramInfoLog(this.id));
	}

	gl.useProgram(this.id);

	// Collect attributes
	_collect(vertexSource, 'attribute', this.attribute);
	for( var a in this.attribute ) {
		this.attribute[a] = gl.getAttribLocation(this.id, a);
	}

	// Collect uniforms
	_collect(vertexSource, 'uniform', this.uniform);
	_collect(fragmentSource, 'uniform', this.uniform);
	for( var u in this.uniform ) {
		this.uniform[u] = gl.getUniformLocation(this.id, u);
	}
};


var WebGLImageFilter = window.WebGLImageFilter = function() {
	var 
		gl = null,
		_drawCount = 0,
		_sourceTexture = null,
		_lastInChain = false,
		_currentFramebufferIndex = -1,
		_tempFramebuffers = [null, null],
		_filterChain = [],
		_width = -1, 
		_height = -1,
		_vertexBuffer = null,
		_currentProgram = null,
		_canvas = document.createElement('canvas');

	var gl = _canvas.getContext("webgl") || _canvas.getContext("experimental-webgl");
	if( !gl ) {
		throw "Couldn't get WebGL context";
	}

	
	this.addFilter = function( name ) {
		var args = Array.prototype.slice.call(arguments, 1);
		var filter = _filter[name];

		_filterChain.push({func:filter, args:args});
	};

	this.reset = function() {
		_filterChain = [];
	};
	
	this.apply = function( image ) {
		_resize( image.width, image.height );
		_drawCount = 0;

		// Create the texture for the input image
		_sourceTexture = gl.createTexture();
		gl.bindTexture(gl.TEXTURE_2D, _sourceTexture);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST); 
		gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);

		// No filters? Just draw
		if( _filterChain.length == 0 ) {
			var program = _compileShader(SHADER.FRAGMENT_IDENTITY);
			_draw();
			return _canvas;
		}

		for( var i = 0; i < _filterChain.length; i++ ) {
			_lastInChain = (i == _filterChain.length-1);
			var f = _filterChain[i];

			f.func.apply(this, f.args || []);
		}

		return _canvas;
	};

	var _resize = function( width, height ) {
		// Same width/height? Nothing to do here
		if( width == _width && height == _height ) { return; }


		_canvas.width = _width = width;
		_canvas.height = _height = height;

		// Create the context if we don't have it yet
		if( !_vertexBuffer ) {
			// Create the vertex buffer for the two triangles [x, y, u, v] * 6
			var vertices = new Float32Array([
				-1, -1, 0, 1,  1, -1, 1, 1,  -1, 1, 0, 0,
				-1, 1, 0, 0,  1, -1, 1, 1,  1, 1, 1, 0
			]);
			_vertexBuffer = gl.createBuffer(),
			gl.bindBuffer(gl.ARRAY_BUFFER, _vertexBuffer);
			gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

			// Note sure if this is a good idea; at least it makes texture loading
			// in Ejecta instant.
			gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
		}

		gl.viewport(0, 0, _width, _height);

		// Delete old temp framebuffers
		_tempFramebuffers = [null, null];
	};

	var _getTempFramebuffer = function( index ) {
		_tempFramebuffers[index] = 
			_tempFramebuffers[index] || 
			_createFramebufferTexture( _width, _height );

		return _tempFramebuffers[index];
	};

	var _createFramebufferTexture = function( width, height ) {
		var fbo = gl.createFramebuffer();
		gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);

		var renderbuffer = gl.createRenderbuffer();
		gl.bindRenderbuffer(gl.RENDERBUFFER, renderbuffer);

		var texture = gl.createTexture();
		gl.bindTexture(gl.TEXTURE_2D, texture);
		gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);

		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
		gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

		gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);

		gl.bindTexture(gl.TEXTURE_2D, null);
		gl.bindFramebuffer(gl.FRAMEBUFFER, null);

		return {fbo: fbo, texture: texture};
	};

	var _draw = function( flags ) {
		var source = null, 
			target = null,
			flipY = false;

		// Set up the source
		if( _drawCount == 0 ) {
			// First draw call - use the source texture
			source = _sourceTexture;
		}
		else {
			// All following draw calls use the temp buffer last drawn to
			source =  _getTempFramebuffer(_currentFramebufferIndex).texture;
		}
		_drawCount++;


		// Set up the target
		if( _lastInChain && !(flags & DRAW.INTERMEDIATE) ) {
			// Last filter in our chain - draw directly to the WebGL Canvas. We may
			// also have to flip the image vertically now
			target = null;
			flipY = _drawCount % 2 == 0;
		}
		else {
			// Intermediate draw call - get a temp buffer to draw to
			_currentFramebufferIndex = (_currentFramebufferIndex+1) % 2;
			target = _getTempFramebuffer(_currentFramebufferIndex).fbo;
		}

		// Bind the source and target and draw the two triangles
		gl.bindTexture(gl.TEXTURE_2D, source);
		gl.bindFramebuffer(gl.FRAMEBUFFER, target);

		gl.uniform1f(_currentProgram.uniform.flipY, (flipY ? -1 : 1) );
		gl.drawArrays(gl.TRIANGLES, 0, 6);
	};

	var _compileShader = function( fragmentSource ) {
		if( fragmentSource.__program ) {
			_currentProgram = fragmentSource.__program;
			gl.useProgram(_currentProgram.id);
			return _currentProgram;
		}

		// Compile shaders
		_currentProgram = new WebGLProgram( gl, SHADER.VERTEX_IDENTITY, fragmentSource );

		var floatSize = Float32Array.BYTES_PER_ELEMENT;
		var vertSize = 4 * floatSize;
		gl.enableVertexAttribArray(_currentProgram.attribute.pos);
		gl.vertexAttribPointer(_currentProgram.attribute.pos, 2, gl.FLOAT, false, vertSize , 0 * floatSize);
		gl.enableVertexAttribArray(_currentProgram.attribute.uv);
		gl.vertexAttribPointer(_currentProgram.attribute.uv, 2, gl.FLOAT, false, vertSize, 2 * floatSize);

		fragmentSource.__program = _currentProgram;
		return _currentProgram;
	};


	var DRAW = { INTERMEDIATE: 1 };

	var SHADER = {};
	SHADER.VERTEX_IDENTITY = [
		'precision highp float;',
		'attribute vec2 pos;',
		'attribute vec2 uv;',
		'varying vec2 vUv;',
		'uniform float flipY;',

		'void main(void) {',
			'vUv = uv;',
			'gl_Position = vec4(pos.x, pos.y*flipY, 0.0, 1.);',
		'}'
	].join('\n');

	SHADER.FRAGMENT_IDENTITY = [
		'precision highp float;',
		'varying vec2 vUv;',
		'uniform sampler2D texture;',

		'void main(void) {',
			'gl_FragColor = texture2D(texture, vUv);',
		'}',
	].join('\n');


	var _filter = {};



	// ----------------------------------------------------------------------------
	// Color Matrix Filter

	_filter.colorMatrix = function( matrix ) {
		// Create a Float32 Array and normalize the offset component to 0-1
		var m = new Float32Array(matrix);
		m[4] /= 255;
		m[9] /= 255;
		m[14] /= 255;
		m[19] /= 255;

		// Can we ignore the alpha value? Makes things a bit faster.
		var shader = (1==m[18]&&0==m[3]&&0==m[8]&&0==m[13]&&0==m[15]&&0==m[16]&&0==m[17]&&0==m[19])
			? _filter.colorMatrix.SHADER.WITHOUT_ALPHA
			: _filter.colorMatrix.SHADER.WITH_ALPHA;
		
		var program = _compileShader(shader);
		gl.uniform1fv(program.uniform.m, m);
		_draw();
	};

	_filter.colorMatrix.SHADER = {};
	_filter.colorMatrix.SHADER.WITH_ALPHA = [
		'precision highp float;',
		'varying vec2 vUv;',
		'uniform sampler2D texture;',
		'uniform float m[20];',

		'void main(void) {',
			'vec4 c = texture2D(texture, vUv);',
			'gl_FragColor.r = m[0] * c.r + m[1] * c.g + m[2] * c.b + m[3] * c.a + m[4];',
			'gl_FragColor.g = m[5] * c.r + m[6] * c.g + m[7] * c.b + m[8] * c.a + m[9];',
			'gl_FragColor.b = m[10] * c.r + m[11] * c.g + m[12] * c.b + m[13] * c.a + m[14];',
			'gl_FragColor.a = m[15] * c.r + m[16] * c.g + m[17] * c.b + m[18] * c.a + m[19];',
		'}',
	].join('\n');
	_filter.colorMatrix.SHADER.WITHOUT_ALPHA = [
		'precision highp float;',
		'varying vec2 vUv;',
		'uniform sampler2D texture;',
		'uniform float m[20];',

		'void main(void) {',
			'vec4 c = texture2D(texture, vUv);',
			'gl_FragColor.r = m[0] * c.r + m[1] * c.g + m[2] * c.b + m[4];',
			'gl_FragColor.g = m[5] * c.r + m[6] * c.g + m[7] * c.b + m[9];',
			'gl_FragColor.b = m[10] * c.r + m[11] * c.g + m[12] * c.b + m[14];',
			'gl_FragColor.a = c.a;',
		'}',
	].join('\n');

	_filter.brightness = function( brightness ) {
		var b = (brightness || 0) + 1;
		_filter.colorMatrix([
				b, 0, 0, 0, 0,
				0, b, 0, 0, 0,
				0, 0, b, 0, 0,
				0, 0, 0, 1, 0
		]);
	};

	_filter.saturation = function( amount ) {
		var x = (amount || 0) * 2/3 + 1;
		var y = ((x-1) *-0.5);
		_filter.colorMatrix([
			x, y, y, 0, 0,
			y, x, y, 0, 0,
			y, y, x, 0, 0,
			0, 0, 0, 1, 0
		]);
	};

	_filter.desaturate = function() {
		_filter.saturation(-1);
	};

	_filter.contrast = function( amount ) {
		var v = (amount || 0) + 1;
		var o = -128 * (v-1);
		
		_filter.colorMatrix([
			v, 0, 0, 0, o,
			0, v, 0, 0, o,
			0, 0, v, 0, o,
			0, 0, 0, 1, 0
		]);
	};

	_filter.negative = function() {
		_filter.contrast(-2);
	};

	_filter.hue = function( rotation ) {
		rotation = (rotation || 0)/180 * Math.PI;
		var cos = Math.cos(rotation),
			sin = Math.sin(rotation),
			lumR = 0.213,
			lumG = 0.715,
			lumB = 0.072;

		_filter.colorMatrix([
				lumR+cos*(1-lumR)+sin*(-lumR),lumG+cos*(-lumG)+sin*(-lumG),lumB+cos*(-lumB)+sin*(1-lumB),0,0,
				lumR+cos*(-lumR)+sin*(0.143),lumG+cos*(1-lumG)+sin*(0.140),lumB+cos*(-lumB)+sin*(-0.283),0,0,
				lumR+cos*(-lumR)+sin*(-(1-lumR)),lumG+cos*(-lumG)+sin*(lumG),lumB+cos*(1-lumB)+sin*(lumB),0,0,
				0, 0, 0, 1, 0
		]);
	};

	_filter.desaturateLuminance = function() {
		_filter.colorMatrix([
			0.2764723, 0.9297080, 0.0938197, 0, -37.1,
			0.2764723, 0.9297080, 0.0938197, 0, -37.1,
			0.2764723, 0.9297080, 0.0938197, 0, -37.1,
			0, 0, 0, 1, 0
		]);
	};

	_filter.sepia = function() {
		_filter.colorMatrix([
			0.393, 0.7689999, 0.18899999, 0, 0,
			0.349, 0.6859999, 0.16799999, 0, 0,
			0.272, 0.5339999, 0.13099999, 0, 0,
			0,0,0,1,0
		]);
	};

	_filter.brownie = function() {
		_filter.colorMatrix([
			0.5997023498159715,0.34553243048391263,-0.2708298674538042,0,47.43192855600873,
			-0.037703249837783157,0.8609577587992641,0.15059552388459913,0,-36.96841498319127,
			0.24113635128153335,-0.07441037908422492,0.44972182064877153,0,-7.562075277591283,
			0,0,0,1,0
		]);
	};

	_filter.vintagePinhole = function() {
		_filter.colorMatrix([
			0.6279345635605994,0.3202183420819367,-0.03965408211312453,0,9.651285835294123,
			0.02578397704808868,0.6441188644374771,0.03259127616149294,0,7.462829176470591,
			0.0466055556782719,-0.0851232987247891,0.5241648018700465,0,5.159190588235296,
			0,0,0,1,0
		]);
	};

	_filter.kodachrome = function() {
		_filter.colorMatrix([
			1.1285582396593525,-0.3967382283601348,-0.03992559172921793,0,63.72958762196502,
			-0.16404339962244616,1.0835251566291304,-0.05498805115633132,0,24.732407896706203,
			-0.16786010706155763,-0.5603416277695248,1.6014850761964943,0,35.62982807460946,
			0,0,0,1,0
		]);
	};

	_filter.technicolor = function() {
		_filter.colorMatrix([
			1.9125277891456083,-0.8545344976951645,-0.09155508482755585,0,11.793603434377337,
			-0.3087833385928097,1.7658908555458428,-0.10601743074722245,0,-70.35205161461398,
			-0.231103377548616,-0.7501899197440212,1.847597816108189,0,30.950940869491138,
			0,0,0,1,0
		]);
	};

	_filter.polaroid = function() {
		_filter.colorMatrix([
			1.438,-0.062,-0.062,0,0,
			-0.122,1.378,-0.122,0,0,
			-0.016,-0.016,1.483,0,0,
			0,0,0,1,0
		]);
	};

	_filter.shiftToBGR = function() {
		_filter.colorMatrix([
			0,0,1,0,0,
			0,1,0,0,0,
			1,0,0,0,0,
			0,0,0,1,0
		]);
	};


	// ----------------------------------------------------------------------------
	// Convolution Filter

	_filter.convolution = function( matrix ) {
		var m = new Float32Array(matrix);
		var pixelSizeX = 1 / _width;
		var pixelSizeY = 1 / _height;

		var program = _compileShader(_filter.convolution.SHADER);
		gl.uniform1fv(program.uniform.m, m);
		gl.uniform2f(program.uniform.px, pixelSizeX, pixelSizeY);
		_draw();
	};

	_filter.convolution.SHADER = [
		'precision highp float;',
		'varying vec2 vUv;',
		'uniform sampler2D texture;',
		'uniform vec2 px;',
		'uniform float m[9];',

		'void main(void) {',
			'vec4 c11 = texture2D(texture, vUv - px);', // top left
			'vec4 c12 = texture2D(texture, vec2(vUv.x, vUv.y - px.y));', // top center
			'vec4 c13 = texture2D(texture, vec2(vUv.x + px.x, vUv.y - px.y));', // top right

			'vec4 c21 = texture2D(texture, vec2(vUv.x - px.x, vUv.y) );', // mid left
			'vec4 c22 = texture2D(texture, vUv);', // mid center
			'vec4 c23 = texture2D(texture, vec2(vUv.x + px.x, vUv.y) );', // mid right

			'vec4 c31 = texture2D(texture, vec2(vUv.x - px.x, vUv.y + px.y) );', // bottom left
			'vec4 c32 = texture2D(texture, vec2(vUv.x, vUv.y + px.y) );', // bottom center
			'vec4 c33 = texture2D(texture, vUv + px );', // bottom right

			'gl_FragColor = ',
				'c11 * m[0] + c12 * m[1] + c22 * m[2] +',
				'c21 * m[3] + c22 * m[4] + c23 * m[5] +',
				'c31 * m[6] + c32 * m[7] + c33 * m[8];',
			'gl_FragColor.a = c22.a;',
		'}',
	].join('\n');


	_filter.detectEdges = function() {
		_filter.convolution.call(this, [
			0, 1, 0,
			1 -4, 1,
			0, 1, 0
		]);
	};

        _filter.sobelX = function() {
                _filter.convolution.call(this, [
                        -1, 0, 1,
                        -2, 0, 2,
                        -1, 0, 1
                ]);
        };

        _filter.sobelY = function() {
                _filter.convolution.call(this, [
                        -1, -2, -1,
                         0,  0,  0,
                         1,  2,  1
                ]);
        };

	_filter.sharpen = function( amount ) {
		var a = amount || 1;
		_filter.convolution.call(this, [
			0, -1*a, 0,
			-1*a, 1 + 4*a, -1*a,
			0, -1*a, 0
		]);
	};

	_filter.emboss = function( size ) {
		var s = size || 1;
		_filter.convolution.call(this, [
			-2*s, -1*s, 0,
			-1*s, 1, 1*s,
			0, 1*s, 2*s
		]);
	};


	// ----------------------------------------------------------------------------
	// Blur Filter

	_filter.blur = function( size ) {
		var blurSizeX = (size/7) / _width;
		var blurSizeY = (size/7) / _height;

		var program = _compileShader(_filter.blur.SHADER);

		// Vertical
		gl.uniform2f(program.uniform.px, 0, blurSizeY);
		_draw(DRAW.INTERMEDIATE);

		// Horizontal
		gl.uniform2f(program.uniform.px, blurSizeX, 0);
		_draw();
	};

	_filter.blur.SHADER = [
		'precision highp float;',
		'varying vec2 vUv;',
		'uniform sampler2D texture;',
		'uniform vec2 px;',

		'void main(void) {',
			'gl_FragColor = vec4(0.0);',
			'gl_FragColor += texture2D(texture, vUv + vec2(-7.0*px.x, -7.0*px.y))*0.0044299121055113265;',
			'gl_FragColor += texture2D(texture, vUv + vec2(-6.0*px.x, -6.0*px.y))*0.00895781211794;',
			'gl_FragColor += texture2D(texture, vUv + vec2(-5.0*px.x, -5.0*px.y))*0.0215963866053;',
			'gl_FragColor += texture2D(texture, vUv + vec2(-4.0*px.x, -4.0*px.y))*0.0443683338718;',
			'gl_FragColor += texture2D(texture, vUv + vec2(-3.0*px.x, -3.0*px.y))*0.0776744219933;',
			'gl_FragColor += texture2D(texture, vUv + vec2(-2.0*px.x, -2.0*px.y))*0.115876621105;',
			'gl_FragColor += texture2D(texture, vUv + vec2(-1.0*px.x, -1.0*px.y))*0.147308056121;',
			'gl_FragColor += texture2D(texture, vUv                             )*0.159576912161;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 1.0*px.x,  1.0*px.y))*0.147308056121;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 2.0*px.x,  2.0*px.y))*0.115876621105;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 3.0*px.x,  3.0*px.y))*0.0776744219933;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 4.0*px.x,  4.0*px.y))*0.0443683338718;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 5.0*px.x,  5.0*px.y))*0.0215963866053;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 6.0*px.x,  6.0*px.y))*0.00895781211794;',
			'gl_FragColor += texture2D(texture, vUv + vec2( 7.0*px.x,  7.0*px.y))*0.0044299121055113265;',
		'}',
	].join('\n');
};

})(window);