@Override
  public String toString() {
    return "VignetteFilterTransformation(center=" + center.toString() + ",color=" + Arrays.toString(
      vignetteColor) + ",start=" + vignetteStart + ",end=" + vignetteEnd + ")";
  }
Performs a vignetting effect, fading out the image at the edges
The directional intensity of the vignetting,
with a default of x = 0.5, y = 0.5, start = 0, end = 0.75
transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/VignetteFilterTransformation.java