code: public static int[] onStackBlurPixels(int[] pix, int w, int h, int radius) {
          if (radius < 0 || radius > 256) {
              throw new RuntimeException("Blur bitmap radius must >= 1 and <=256.");
          }
  
          if (pix == null) {
              throw new RuntimeException("Blur bitmap pix isn't null.");
          }
  
          if (pix.length < w * h) {
              throw new RuntimeException("Blur bitmap pix length must >= w * h.");
          }
  
          // Jni Pixels Blur
          nativeStackBlurPixels(pix, w, h, radius);
  
          return (pix);
      }
docs: StackBlur By Jni Pixels
  
  @param pix    Original Image, you can call:
  <p>
  int w = bitmap.getWidth();
  int h = bitmap.getHeight();
  int[] pix = new int[w * h];
  bitmap.getPixels(pix, 0, w, 0, 0, w, h);
  <p>
  // Jni Pixels Blur
  onStackBlurPixels(pix, w, h, radius);
  <p>
  bitmap.setPixels(pix, 0, w, 0, 0, w, h);
  <p>
  @param radius Blur radius
  @return Image Bitmap