Home » html5 » HT for Web基于HTML5的图像操作(三)

上篇采用了HTML5的Canvas的globalCompositeOperation属性达到了染色效果,其实CSS也提供了一些常规图像变化的设置参数,关于CSS的过滤器Filter设置可参考 http://www.html5rocks.com/en/tutorials/filters/understanding-css/,CSS的设置的确很方便,不需要我们了解底层实现逻辑,仅需要提供简单的设置参数值即可,但这样的方式毕竟无法达到随心所欲变化的效果,这有点想OpenGL早期只能通过Fixed Function Pipeline进行开发,和如今采用Shading Language可实现丰富多彩变化的质变,因此这篇我们将采用WebGL的SL代码方式折腾点更好玩的效果。

Screen Shot 2014-11-23 at 6.00.06 PM

第一篇我们已经提到图像操作的本质是对输入输出的数据变化,因此染色仅是最简单直观的基本变化,通过WebGL的SL代码我们甚至可以实现图像扭曲等变化效果,先上张最终变化效果的截图,原图就是Hightopo官网的banner,染色+扭曲的效果如上:

Vertex代码如下:

	attribute vec2 aVertexPosition;
	attribute vec2 aTexturePosition;
	varying vec2 vTexturePosition;
	void main() {
		vTexturePosition = aTexturePosition;
		gl_Position = vec4(aVertexPosition, 0.0, 1.0); 
	}

Fragment代码如下:

	precision mediump float;

	varying vec2 vTexturePosition;            
	uniform sampler2D uSampler; 

	uniform vec4 uColor; 
	uniform float uRadius;
	uniform float uAngle;
	uniform vec2 uCenter;            

	void main() {                   
	   vec2 vec = vTexturePosition - uCenter;
	   float distance = length(vec);
	   if (distance < uRadius) {
		   float ratio = (uRadius - distance) / uRadius;
		   float angle = ratio * ratio * uAngle;
		   float s = sin(angle);
		   float c = cos(angle);
		   vec = vec2(vec.x * c - vec.y * s, vec.x * s + vec.y * c);
	   }                               
	   gl_FragColor = texture2D(uSampler, uCenter+vec) * uColor; 
	}

相应JavaScript代码如下:

	gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
	gl.clearColor(0.0, 0.0, 0.0, 1.0);
	gl.clear(gl.COLOR_BUFFER_BIT);

	vertexShader = loadShaderFromDOM("shader-vs");
	fragmentShader = loadShaderFromDOM("shader-fs");

	var program = gl.createProgram();
	gl.attachShader(program, vertexShader);
	gl.attachShader(program, fragmentShader);
	gl.linkProgram(program);

	gl.useProgram(program);

	var vertexBuffer = gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
		-0.7, 0.7,
		-0.7, -0.7,
		0.7, 0.7,
		-0.7, -0.7,
		0.7, -0.7,
		0.7, 0.7
	]), gl.STATIC_DRAW);
	var vertexLocation = gl.getAttribLocation(program, "aVertexPosition");
	gl.vertexAttribPointer(vertexLocation, 2, gl.FLOAT, false, 0, 0);
	gl.enableVertexAttribArray(vertexLocation);

	var textureBuffer = gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER, textureBuffer);
	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
		0, 1,
		0, 0,
		1, 1,
		0, 0,
		1, 0,
		1, 1
	]), gl.STATIC_DRAW);
	var textureLocation = gl.getAttribLocation(program, "aTexturePosition");
	gl.vertexAttribPointer(textureLocation, 2, gl.FLOAT, false, 0, 0);
	gl.enableVertexAttribArray(textureLocation);

	gl.activeTexture(gl.TEXTURE0);
	gl.bindTexture(gl.TEXTURE_2D, texture);
	gl.uniform1i(gl.getUniformLocation(program, 'uSampler'), 0);                
	gl.uniform4fv(gl.getUniformLocation(program, 'uColor'), toRGBA(formPane.v('color')));
	gl.uniform1f(gl.getUniformLocation(program, 'uRadius'), formPane.v('radius'));
	gl.uniform1f(gl.getUniformLocation(program, 'uAngle'), formPane.v('angle'));
	gl.uniform2fv(gl.getUniformLocation(program, 'uCenter'), [formPane.v('centerX'), 1-formPane.v('centerY')]);            
	gl.drawArrays(gl.TRIANGLES, 0, 6);
}

以上Vertext和Fragment的代码很多很容易理解,采用HT for WebFromPane插件很容易实现控制参数面板可进行编辑实时呈现变化效果,以下为操作控制面板动态变化的视频效果:http://v.youku.com/v_show/id_XODMzMTU0OTA0.html

Screen Shot 2014-11-23 at 6.02.26 PM

最后如果你耐心细致地阅读到此,对前端游戏开发感兴趣,感觉自己悟性不错,愿意在厦门发展的同学可与联系我,我的邮箱为eric@… 省略部分你应该知道的,不限制性别、学历和年龄,只要你想用心做自己喜欢的事,我期待着与你交流和加盟!