Cocos Shader 不规则图片描边效果

开发中碰到需要给不规则图片添加秒变效果，效果如下

代码如下：

CCEffect %{
  techniques:
  - passes:
    - vert: vs
      frag: fs
      blendState:
        targets:
        - blend: true
      rasterizerState:
        cullMode: none
      properties:
        texture: { value: white }
        alphaThreshold: { value: 0.5 }
        outlineWidth: { value: 0.01 }
}%


CCProgram vs %{
  precision highp float;

  #include <cc-global>
  #include <cc-local>

  in vec3 a_position;
  in vec4 a_color;
  out vec4 v_color;

  #if USE_TEXTURE
  in vec2 a_uv0;
  out vec2 v_uv0;
  #endif

  void main () {
    vec4 pos = vec4(a_position, 1);

    #if CC_USE_MODEL
    pos = cc_matViewProj * cc_matWorld * pos;
    #else
    pos = cc_matViewProj * pos;
    #endif

    #if USE_TEXTURE
    v_uv0 = a_uv0;
    #endif

    v_color = a_color;

    gl_Position = pos;
  }
}%


CCProgram fs %{
  precision highp float;
  
  #include <alpha-test>
  // #include <texture>
  #include <cc-global>

  in vec4 v_color;

  #if USE_TEXTURE
  in vec2 v_uv0;
  uniform sampler2D texture;
  #endif

  //cocos规定在shader中所有非sampler的uniform都应以block形式声明
  uniform InputData{
    float outlineWidth;  //外部程序输入描边宽度1-1.0。
  };
 
  //检查pos点是否需要描边
  bool checkIsMakeOutline(vec2 pos){
    //alpha检测值
    float alpha = 0.1;
    vec4 color = texture(texture, pos);
    if(color.a <= alpha || outlineWidth == 0.0)return false;
 
    //检测当前点周围的8个点的alpha值
    color = texture2D(texture, pos + vec2(0, outlineWidth));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(outlineWidth, outlineWidth));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(outlineWidth, 0));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(outlineWidth, -outlineWidth));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(0, -outlineWidth));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(-outlineWidth, -outlineWidth));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(-outlineWidth, 0));
    if(color.a <= alpha)return true;
    color = texture2D(texture, pos + vec2(-outlineWidth, outlineWidth));
    if(color.a <= alpha)return true;
    
    //当前点已是纹理边缘
    if(pos.x <= outlineWidth || pos.x >= 1.0 - outlineWidth)return true;
    if(pos.y <= outlineWidth || pos.y >= 1.0 - outlineWidth)return true;
 
    return false;
  }
  
  void main () {
    vec4 o = vec4(1, 1, 1, 1);

    #if USE_TEXTURE
    o *= texture(texture, v_uv0);
      #if CC_USE_ALPHA_ATLAS_TEXTURE
      o.a *= texture2D(texture, v_uv0 + vec2(0, 0.5)).r;
      #endif
    #endif
 
    o *= v_color;
 
    ALPHA_TEST(o);
 
    if(checkIsMakeOutline(v_uv0)){
      //检查到v_uv0点需要描边，直接改变颜色值
      o = vec4(1, 1, 0.7, 1);
    }

    gl_FragColor = o;
  }

}%