I have an ImageView with bitmap in it. This bitmap has alpha channel and transparent pixels. When i try to use ColorFiter with Mode.OVERLAY (since honeycomb) - provided color overlay the whole imageview (whole rect), but i want only to overlay non transparent pixels. How can i clip the imageview's canvas to perform filter where i want ?
UPDATED
I have grey image in png:
When i try to use MODE_ATOP i get:
When i use OVERLAY i get:
And what i want to get:
There's probably a more efficient way to do this (maybe by creating a ColorMatrixColorFilter
to approximate it), but since Mode.OVERLAY
appear to be hard to simplify otherwise, here's some sample code that should implement what you want:
public class MyActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final ImageView imageView = new ImageView(this);
setContentView(imageView);
final Paint paint = new Paint();
Canvas c;
final Bitmap src = BitmapFactory.decodeResource(getResources(),
android.R.drawable.sym_def_app_icon);
final int overlayColor = Color.RED;
final Bitmap bm1 = Bitmap.createBitmap(src.getWidth(), src.getHeight(), Config.ARGB_8888);
c = new Canvas(bm1);
paint.setColorFilter(new PorterDuffColorFilter(overlayColor, PorterDuff.Mode.OVERLAY));
c.drawBitmap(src, 0, 0, paint);
final Bitmap bm2 = Bitmap.createBitmap(src.getWidth(), src.getHeight(), Config.ARGB_8888);
c = new Canvas(bm2);
paint.setColorFilter(new PorterDuffColorFilter(overlayColor, PorterDuff.Mode.SRC_ATOP));
c.drawBitmap(src, 0, 0, paint);
paint.setColorFilter(null);
paint.setXfermode(new AvoidXfermode(overlayColor, 0, Mode.TARGET));
c.drawBitmap(bm1, 0, 0, paint);
imageView.setImageBitmap(bm2);
}
}
In short, we draw the source bitmap and color using the OVERLAY
mode, and then using a secondary bitmap (composited using SRC_ATOP
mode), we combine it using AvoidXfermode
to not draw over the transparent pixels.
Original image:
Result: