js使用webgl

painter.prototype.initWebGL = function() {
	// attempt to get a webgl context
	try {
		var gl = this.gl = this.canvas.getContext('webgl') || this.canvas.getContext('experimental-webgl');
	} catch (e) {
		return false;
	}
	
	if (!gl) {
		return false;
	}

	// init buffers
	this.buffer = gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER, this.buffer);
	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 0, 1, 1, 0, 1, 1]), gl.STATIC_DRAW);

	// The main YCbCrToRGBA Shader
	this.program = gl.createProgram();
	gl.attachShader(this.program, this.compileShader(gl.VERTEX_SHADER, SHADER_VERTEX_IDENTITY));
	gl.attachShader(this.program, this.compileShader(gl.FRAGMENT_SHADER, SHADER_FRAGMENT_YCBCRTORGBA));
	gl.linkProgram(this.program);
	
	if( !gl.getProgramParameter(this.program, gl.LINK_STATUS) ) {
		throw new Error(gl.getProgramInfoLog(this.program));
	}
	
	gl.useProgram(this.program);
	
	// setup textures
	this.YTexture = this.createTexture(0, 'YTexture');
	this.CBTexture = this.createTexture(1, 'CBTexture');
	this.CRTexture = this.createTexture(2, 'CRTexture');
	
	var vertexAttr = gl.getAttribLocation(this.program, 'vertex');
	gl.enableVertexAttribArray(vertexAttr);
	gl.vertexAttribPointer(vertexAttr, 2, gl.FLOAT, false, 0, 0);


	// Shader for the loading screen
	this.loadingProgram = gl.createProgram();
	gl.attachShader(this.loadingProgram, this.compileShader(gl.VERTEX_SHADER, SHADER_VERTEX_IDENTITY));
	gl.attachShader(this.loadingProgram, this.compileShader(gl.FRAGMENT_SHADER, SHADER_FRAGMENT_LOADING));
	gl.linkProgram(this.loadingProgram);

	gl.useProgram(this.loadingProgram);

	vertexAttr = gl.getAttribLocation(this.loadingProgram, 'vertex');
	gl.enableVertexAttribArray(vertexAttr);
	gl.vertexAttribPointer(vertexAttr, 2, gl.FLOAT, false, 0, 0);
	
	return true;
};