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. I have 2 questions: 1. How can I draw an outer shadow (I can only seem to draw a shadow with a x or y offset) 2. How can I draw the shadow so that it does not have the artifacts shown in the attached image. Code: ``` ![public Bitmap getRoundedCornerBitmap(Bitmap bitmap, float cornerRadius) { Bitmap output = Bitmap.createBitmap(bitmap.getWidth()+6, bitmap.getHeight() +6, Config.ARGB_8888); Canvas canvas = new Canvas(output); final int color = 0xff424242; int shadowRadius = getDipsFromPixel(3); final Rect imageRect = new Rect(shadowRadius, shadowRadius, bitmap.getWidth(), bitmap.getHeight()); final RectF rectF = new RectF(imageRect); // This does not achieve the desired effect Paint shadowPaint = new Paint(); shadowPaint.setAntiAlias(true); shadowPaint.setColor(Color.BLACK); shadowPaint.setShadowLayer((float)shadowRa…

Accepted Answer

Here we go

Yup I still dig the Nexus S

First of all, please stop masking bitmaps that way, you can accomplish this without allocating another `Bitmap`, checkout this blog post about how to draw rounded (and actually any shape) images.

Second using that `Drawable` you probably can figure out how to add your shadow, just make sure it does not get clipped, on 18+ you could use `ViewOverlay`s for that, also keep in mind that there are several unsupported drawing operations for hardware accelerated layers, that includes `setShadowLayer` and `BlurMaskFilter`, if performance is not an issue for you, you can disable it as always:

```
if (SDK_INT >= HONEYCOMB) {
  view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
}
```

And use `setShadowLayer` as you were trying already:

```
somePaint.setShadowLayer(shadowSize, deltaX, deltaY, shadowColor);
```

For a sample please check the link at the end.

If you still want to be hardware accelerated you will have to fake it at risk of overdrawing, you could use a radial gradient or draw another oval blurring it yourself (as mentioned before can't use `BlurMaskFilter`) or use a pre-blurred `Bitmap` (more masking).

For such a subtle shadow I would rather just go flat if performance is required, the full sauce is in the banana stand.

Update: Starting L you can use real shadows.

Drawing an outer shadow when drawing an image

Solution

Problem