Here is how to create a clipping area the shape of a circle:
Path path = new Path();
path.addCircle(200,200,100,Direction.CW);
c.clipPath(path); // c is a Canvas
Now there's a clipping area on the Canvas which prevents drawing anything outside the bounds of that circle. But, what if I want to have the clipping area be shaped like a donut (or whatever)?
I tried playing around with creating a second Path and using toggleInverseFillType on it and then adding that to the original path, but that doesn't seem to work.
Alternatively, instead of using a Path, is it possible to just create a Bitmap to use as a mask and set it as a clipping mask on the Canvas somehow?
EDIT: The answer is exactly what I needed with one small addition. When doing multiple operations on a canvas, always use Op.REPLACE on the first clipPath call. That will replace any existing clipPath on that Canvas.
For reference, here is what I discovered what the 6 different Region.Op values mean. Imagine a venn diagram with 2 circles. "B" is the part where the 2 circles overlap. "A" is the non-overlapping left circle. "C" is the non-overlapping right circle.
c.clipPath(a,Region.Op.REPLACE);
c.clipPath(b,???);
Region.Op.DIFFERENCE -> A..
Region.Op.INTERSECT -> .B.
Region.Op.REPLACE -> .BC
Region.Op.REVERSE_DIFFERENCE -> ..C
Region.Op.UNION -> ABC
Region.Op.XOR -> A.C
The "." indicates the part that isn't drawn. Sorry if that's not particularly clear. It's hard to describe well without graphics.
From the Canvas
javadoc:
Canvas#clipPath(Path path, Region.Op op)
- Modify the current clip with the specified path.
So, for your donut example:
Canvas#clipPath( Path )
with larger circle Path
.Call the Canvas#clipPath( Path, Region.Op )
method on your canvas with the smaller circle Path
for the first argument and the appropriate Region.Op
enum value for the second argument.
Path largePath = new Path();
largePath.addCircle(200,200,100,Direction.CW);
Path smallPath = new Path();
smallPath.addCircle(200,200,40,Direction.CW);
c.clipPath(largePath); // c is a Canvas
c.clipPath(smallPath, Region.Op.DIFFERENCE);
Again, modify the Region.Op
enum value to get different effects...