// blur.frag

#ifdef GL_ES
precision mediump float;
#endif

varying vec4 v_fragmentColor;
varying vec2 v_texCoord;

// 贴图尺寸
uniform vec2 resolution;
// 模糊半径
uniform float blurRadius;

vec4 blur(vec2);

void main(void)
{
	vec4 col = blur(v_texCoord);
	gl_FragColor = vec4(col) * v_fragmentColor;
}

vec4 blur(vec2 p)
{
    vec4 col = vec4(0);
    float r = blurRadius;

    // 单位尺寸
    vec2 unit = 1.0 / resolution.xy;
    // 步长
    float step = r / 5.0;
    // 总权重
    float allWeight = 0.0;
    
    for(float x = -r; x < r; x += step)
    {
        for(float y = -r; y < r; y += step)
        {
            // 权重
            float weight = (r - abs(x)) * (r - abs(y));
            // 当前像素颜色 * 权重
            col += texture2D(CC_Texture0, p + vec2(x * unit.x, y * unit.y)) * weight;
            allWeight += weight;
        }
    }
    return col / allWeight;
}