static int getGreyColor(int color) {
    final int r = (color >> 16) & 0xFF;
    final int g = (color >> 8) & 0xFF;
    final int b = color & 0xFF;

    // see: https://en.wikipedia.org/wiki/Relative_luminance
    final int luminance = (int) (0.2126 * r + 0.7152 * g + 0.0722 * b);

    return 0xFF000000 | luminance << 16 | luminance << 8 | luminance;
  }
Applies a grey-scale effect on the bitmap using the slow {@link Bitmap#setPixel(int, int, int)}
method.
samples/showcase/src/main/java/com/facebook/fresco/samples/showcase/postprocessor/SlowGreyScalePostprocessor.java