cocos2d-x之字体描边效果shader实现

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#ifdef GL_ESprecision highp float;#endif  uniform sampler2D u_texture;varying vec2 v_texCoord;varying vec4 v_fragmentColor;//模糊blur的步长，这里只是demo，正式使用由外部传入（uniform类型）const vec2 step = vec2(0.003, 0.002);void main(void){ //获得当前点的颜色    vec3 color = texture2D(u_texture, v_texCoord).rgb;    //该权值用于自身对结果的影响    float weight = 30.0;    //加入alpha权重，alpha越大，权值assess越小    float assess = pow(texture2D(u_texture, v_texCoord).a, 3)*weight;    //开始计算平均alpha值    float alpha = assess;    //以下为高斯模糊（仅对alpha）    alpha += texture2D( u_texture, v_texCoord.st + vec2( -3.0*step.x, -3.0*step.y ) ).a;alpha += texture2D( u_texture, v_texCoord.st + vec2( -2.0*step.x, -2.0*step.y ) ).a;alpha += texture2D( u_texture, v_texCoord.st + vec2( -1.0*step.x, -1.0*step.y ) ).a;alpha += texture2D( u_texture, v_texCoord.st + vec2( 0.0 , 0.0) ).a;alpha += texture2D( u_texture, v_texCoord.st + vec2( 1.0*step.x,  1.0*step.y ) ).a;alpha += texture2D( u_texture, v_texCoord.st + vec2( 2.0*step.x,  2.0*step.y ) ).a;alpha += texture2D( u_texture, v_texCoord.st + vec2( 3.0*step.x, -3.0*step.y ) ).a;alpha /= 7.0+assess;//alpha越大，对颜色影响越小    color = clamp(color + (alpha - 1.0), 0, 1.0);    //进一步加强颜色的区分    color = pow(color, vec3(3.0, 3.0, 3.0));     //输出    gl_FragColor = vec4(color.r, color.g, color.b, alpha);}
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