cocos2d-js Shader系列2：在cc.Sprite上使用Shader（黑白、灰度、造旧效果）

在Sprite中使用Shader做特殊的颜色处理比较简单，只需要把Shader程序绑定到Sprite上即可：

sprite.shaderProgram = alphaTestShader;

Cocos2d内置了一些Shader，详细可以看代码:

其中，CCShaderCache缓存了一些Shader实例，而GLProgram则对gl的api做了简单的封装让接口更友好。

需要注意的是，使用GLProgram编译shader程序时，cocos2d会自动加入了一些参数。

    _compileShader: function (shader, type, source) {
        if (!source || !shader)
            return false;
        //var preStr = (type == this._glContext.VERTEX_SHADER) ? "precision highp float;\n" : "precision mediump float;\n";
        source = "precision highp float;        \n"
            + "uniform mat4 CC_PMatrix;         \n"
            + "uniform mat4 CC_MVMatrix;        \n"
            + "uniform mat4 CC_MVPMatrix;       \n"
            + "uniform vec4 CC_Time;            \n"
            + "uniform vec4 CC_SinTime;         \n"
            + "uniform vec4 CC_CosTime;         \n"
            + "uniform vec4 CC_Random01;        \n"
            + "//CC INCLUDES END                \n" + source;
        this._glContext.shaderSource(shader, source);
        this._glContext.compileShader(shader);
        var status = this._glContext.getShaderParameter(shader, this._glContext.COMPILE_STATUS);
        if (!status) {
            cc.log("cocos2d: ERROR: Failed to compile shader:\n" + this._glContext.getShaderSource(shader));
            if (type == this._glContext.VERTEX_SHADER)
                cc.log("cocos2d: \n" + this.vertexShaderLog());
            else
                cc.log("cocos2d: \n" + this.fragmentShaderLog());
        }
        return ( status == 1 );
    }

另外，绑定到sprite之后，cocos2d会自动设置一些值，我们只需要事先做个绑定即可，而这个绑定操作，也是有友好封装的。具体可以顺藤摸瓜看代码。

                program.addAttribute(cc.ATTRIBUTE_NAME_POSITION, cc.VERTEX_ATTRIB_POSITION);
                program.addAttribute(cc.ATTRIBUTE_NAME_COLOR, cc.VERTEX_ATTRIB_COLOR);
                program.addAttribute(cc.ATTRIBUTE_NAME_TEX_COORD, cc.VERTEX_ATTRIB_TEX_COORDS);

在sprite上做效果，无非就是一些颜色变换或者说是滤镜而已。由于cocos没有原生的滤镜，不像flash那么方便，那么我们就要自己动手丰衣足食了。

下边实现两个灰度和造旧sepia的效果，类似Flash的ShaderFilter一样。

（绿色球就是原图，上下2个小球分别用不同的sepia参数得到的造旧效果）

var sugar4 = Sugar.create(0,0,2);
        sugar4.x = size.width/4;
        sugar4.y = size.height/1.5;
        this.addChild(sugar4);
        sugar4.scale = 3;
        var sugar = Sugar.create(0,0,2);
        sugar.x = size.width/2;
        sugar.y = size.height/2;
        this.addChild(sugar);
        sugar.scale = 3;
        var sugar2 = Sugar.create(0,0,2);
        sugar2.x = size.width/3;
        sugar2.y = size.height/3;
        this.addChild(sugar2);
        sugar2.scale = 2;
        var sugar3 = Sugar.create(0,0,2);
        sugar3.x = size.width/3*2;
        sugar3.y = size.height/3*2;
        this.addChild(sugar3);
        sugar3.scale = 2;
        Filter.grayScale(sugar);
        Filter.sepia(sugar2, 0.5);
        Filter.sepia(sugar3, 0.9);

Filter类的代码：

/**
* Created by kenkozheng on 2014/11/4.
*/
/**
* 只能用于控制Sprite的色调等，目标是实现类似Flash的内置基本滤镜
* 静态类
*/
var Filter = {
    DEFAULT_VERTEX_SHADER:
        "attribute vec4 a_position; \n"
        + "attribute vec2 a_texCoord; \n"
        + "varying mediump vec2 v_texCoord; \n"
        + "void main() \n"
        + "{ \n"
        + "    gl_Position = (CC_PMatrix * CC_MVMatrix) * a_position;  \n"
        + "    v_texCoord = a_texCoord; \n"
        + "}",
    GRAY_SCALE_FRAGMENT_SHADER:
        "varying vec2 v_texCoord;   \n"
        + "uniform sampler2D CC_Texture0; \n"
        + "void main() \n"
        + "{  \n"
        + "    vec4 texColor = texture2D(CC_Texture0, v_texCoord);  \n"
        + "    float gray = texColor.r * 0.299 + texColor.g * 0.587 + texColor.b * 0.114; \n"
        + "    gl_FragColor = vec4(gray, gray, gray, texColor.a);  \n"
        + "}",
    SEPIA_FRAGMENT_SHADER:
        "varying vec2 v_texCoord;   \n"
        + "uniform sampler2D CC_Texture0; \n"
        + "uniform float u_degree; \n"
        + "void main() \n"
        + "{  \n"
        + "    vec4 texColor = texture2D(CC_Texture0, v_texCoord);  \n"
        + "    float r = texColor.r * 0.393 + texColor.g * 0.769 + texColor.b * 0.189; \n"
        + "    float g = texColor.r * 0.349 + texColor.g * 0.686 + texColor.b * 0.168; \n"
        + "    float b = texColor.r * 0.272 + texColor.g * 0.534 + texColor.b * 0.131; \n"
        + "    gl_FragColor = mix(texColor, vec4(r, g, b, texColor.a), u_degree);  \n"
        + "}",
    programs:{},
    /**
     * 灰度
     * @param sprite
     */
    grayScale: function (sprite) {
        var program = Filter.programs["grayScale"];
        if(!program){
            program = new cc.GLProgram();
            program.initWithVertexShaderByteArray(Filter.DEFAULT_VERTEX_SHADER, Filter.GRAY_SCALE_FRAGMENT_SHADER);
            program.addAttribute(cc.ATTRIBUTE_NAME_POSITION, cc.VERTEX_ATTRIB_POSITION);        //cocos会做初始化的工作
            program.addAttribute(cc.ATTRIBUTE_NAME_TEX_COORD, cc.VERTEX_ATTRIB_TEX_COORDS);
            program.link();
            program.updateUniforms();
            Filter.programs["grayScale"] = program;
        }
        gl.useProgram(program.getProgram());
        sprite.shaderProgram = program;
    },
    /**
     * 造旧
     * @param sprite
     * @param degree 旧的程度 0~1
     */
    sepia: function (sprite, degree) {
        var program = Filter.programs["sepia"+degree];
        if(!program){
            program = new cc.GLProgram();
            program.initWithVertexShaderByteArray(Filter.DEFAULT_VERTEX_SHADER, Filter.SEPIA_FRAGMENT_SHADER);
            program.addAttribute(cc.ATTRIBUTE_NAME_POSITION, cc.VERTEX_ATTRIB_POSITION);        //cocos会做初始化的工作
            program.addAttribute(cc.ATTRIBUTE_NAME_TEX_COORD, cc.VERTEX_ATTRIB_TEX_COORDS);
            program.link();
            program.updateUniforms();
            var degreeLocation = program.getUniformLocationForName("u_degree");
            program.setUniformLocationF32(degreeLocation, degree);
            Filter.programs["sepia"+degree] = program;
        }
        gl.useProgram(program.getProgram());
        sprite.shaderProgram = program;
    }
};