precision highp float;
varying highp vec2 uv0;
uniform sampler2D u_InputTex;
uniform float u_Angle;
uniform float u_Strength;
uniform vec4 u_ScreenParams;
float normpdf(in float x, in float sigma)
{
	return 0.39894*exp(-0.5*x*x/(sigma*sigma))/sigma;
}
vec4 gaussianBlur(sampler2D i_InputTex, vec2 i_Uv, vec2 i_Dir, float i_Strength)
{
    const int  radius = 32;
    // float s = i_Strength;
    float sigma = 4.0;
    float first = normpdf(0.0, sigma);
    float weight = 0.5 * 1.02 + 0.5;

    vec4 sum            = vec4(0.0);
    vec4 result         = vec4(0.0);
    vec2 unit_uv        = i_Dir;
    vec4 curColor       = texture2D(i_InputTex, i_Uv);
    vec4 centerPixel    = pow(curColor, vec4(2.2))*weight;
    float sum_weight    = weight;
    #ifdef GLOWSAMPLE
    float s = float(GLOWSAMPLE);
    for(float i=1.;i<=abs(s);i+=1.0)
    {
        vec2 curRightCoordinate = i_Uv+float(i)*unit_uv;
        vec2 curLeftCoordinate  = i_Uv+float(-i)*unit_uv;
        vec4 rightColor = texture2D(i_InputTex, curRightCoordinate);
        vec4 leftColor = texture2D(i_InputTex, curLeftCoordinate);
        weight = (normpdf(float(i) / s * 15.0, sigma) / first - 0.5) * 1.02 + 0.5;
        sum+=pow(rightColor, vec4(2.2))*weight;
        sum+=pow(leftColor, vec4(2.2))*weight;
        sum_weight+=weight*2.0;
    }
    #endif
    result = (sum+centerPixel)/sum_weight; 
    return pow(clamp(result, 0.0, 1.0), vec4(1.0 / 2.2));
}

void main()
{
    float theta = u_Angle * 3.1415926 / 180.;
    vec2 dir = vec2(cos(theta), sin(theta)) / 720.0;
    vec4 color = gaussianBlur(u_InputTex, uv0, dir, u_Strength);
    gl_FragColor = color;
}