Android - alpha/shadow transformation for Picasso (This allows you to draw a transparent black shade over the source image)
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import com.squareup.picasso.Transformation;
public class AlphaTransformation implements Transformation {
/* The shade alpha of black to apply */
private int mAlpha;
/**
* Integer Constructor
*
* @param alpha the alpha shade to apply
*/
public AlphaTransformation(int alpha) {
// Clamp the alpha value to 0..255
mAlpha = Math.max(0, Math.min(255, alpha));
}
/**
* Float Constructor
*
* @param percent the alpha percentage from 0..1
*/
public AlphaTransformation(float percent) {
// Clamp the float value to 0..1
mAlpha = (int) ((Math.max(0, Math.min(1, percent))) * 255);
}
/**
* Transform the source bitmap into a new bitmap. If you create a new bitmap instance, you must
* call {@link android.graphics.Bitmap#recycle()} on {@code source}. You may return the original
* if no transformation is required.
*/
@Override
public Bitmap transform(Bitmap source) {
Paint paint = new Paint();
Bitmap output =
Bitmap.createBitmap(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);
// Create canvas and draw the source image
Canvas canvas = new Canvas(output);
canvas.drawBitmap(source, 0, 0, paint);
// Setup the paint for painting the shade
paint.setColor(Color.BLACK);
paint.setAlpha(mAlpha);
// Paint the shade
canvas.drawPaint(paint);
// Recycle and return
source.recycle();
return output;
}
/**
* Returns a unique key for the transformation, used for caching purposes. If the transformation
* has parameters (e.g. size, scale factor, etc) then these should be part of the key.
*/
@Override
public String key() {
return "shade:" + mAlpha;
}
}