Drawing an outer shadow when drawing an image

Question

I currently create a rounded version of an image in my app by drawing to a canvas. I would like to draw a faint outershadow around the image, but I cant quite get it right.

Answer 1

I wanted a similar effect, but on an AppWidget so unfortunately I couldn't use @EvelioTarazona's solution. This is what I came up with, it should work with a bitmap of any shape.

    final Bitmap src = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
    final Bitmap shadow = addShadow(src, src.getHeight(), src.getWidth(), Color.BLACK, 3, 1, 3);
    final ImageView iv = (ImageView)findViewById(R.id.image);
    iv.setImageBitmap(shadow);

 public Bitmap addShadow(final Bitmap bm, final int dstHeight, final int dstWidth, int color, int size, float dx, float dy) {
    final Bitmap mask = Bitmap.createBitmap(dstWidth, dstHeight, Config.ALPHA_8);

    final Matrix scaleToFit = new Matrix();
    final RectF src = new RectF(0, 0, bm.getWidth(), bm.getHeight());
    final RectF dst = new RectF(0, 0, dstWidth - dx, dstHeight - dy);
    scaleToFit.setRectToRect(src, dst, ScaleToFit.CENTER);

    final Matrix dropShadow = new Matrix(scaleToFit);
    dropShadow.postTranslate(dx, dy);

    final Canvas maskCanvas = new Canvas(mask);
    final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    maskCanvas.drawBitmap(bm, scaleToFit, paint);
    paint.setXfermode(new PorterDuffXfermode(Mode.SRC_OUT));
    maskCanvas.drawBitmap(bm, dropShadow, paint);

    final BlurMaskFilter filter = new BlurMaskFilter(size, Blur.NORMAL);
    paint.reset();
    paint.setAntiAlias(true);
    paint.setColor(color);
    paint.setMaskFilter(filter);
    paint.setFilterBitmap(true);

    final Bitmap ret = Bitmap.createBitmap(dstWidth, dstHeight, Config.ARGB_8888);
    final Canvas retCanvas = new Canvas(ret);
    retCanvas.drawBitmap(mask, 0,  0, paint);
    retCanvas.drawBitmap(bm, scaleToFit, null);
    mask.recycle();
    return ret;
}