kernel vec4 coreImageKernel(__sampler image1,
                            vec4 args1, vec4 args2, vec2 u_endPosition) {
  //  float u_blurRadius = args1.x;
  //  float u_gradientSize  = args1.y;
  //  float u_size  = args1.z;
  //  float blurSteps = args1.w;
  vec2 u_startPosition = args2.xy;
  vec2 u_delta = vec2(-0.5, 0.5);
  vec4 color = vec4(0.0);
  float total = 0.0;
  float percent;
  float weight;
  vec4 samplePix;
  vec2 dc = destCoord();
  dc.y = args2.w - dc.y;

  vec2 normal = normalize(vec2(u_startPosition.y - u_endPosition.y, u_endPosition.x - u_startPosition.x));
  float radius = args1.x * smoothstep(
    0.0,
    1.0,
    (abs(dot(dc - u_startPosition, normal)) - args1.z) / args1.y
  );

  for (float t = -args1.w; t <= args1.w; t++) {
    percent = t / args1.w;

    vec4 samplePix = sample(image1, samplerTransform(image1, destCoord() + u_delta * percent * radius));
    weight = (1.0 - abs(percent));
    color += samplePix * weight;
    total += weight;
  }

  return color / total;
}