Apply gray filter to ImageView in Android

The following code is to apply gray filter to ImageView and reset the filter.

• Reference: https://stackoverflow.com/questions/28308325/androidset-gray-scale-filter-to-imageview

This code requires minSdkVersion of 16.

public class ViewUtils {
    public static void applyGrayFilter(ImageView imageView) {
        ColorMatrix matrix = new ColorMatrix();
        matrix.setSaturation(0);  //0 means grayscale
        ColorMatrixColorFilter cf = new ColorMatrixColorFilter(matrix);
        imageView.setColorFilter(cf);
        imageView.setImageAlpha(128);   // 128 = 0.5
    }

    public static void resetGrayFilter(ImageView imageView) {
        imageView.setColorFilter(null);
        imageView.setImageAlpha(255);
    }
}