Canvas.clipPath(Path) not clipping as expected
android, android-canvas, drawing, image-clipping
Solution
Are you using HC or above or otherwise using hardware acceleration?
If so, clipPath is unsupported and problematic.
developer.android.com/guide/topics/graphics/hardware-accel.html.
Problem
I'm trying to clip a canvas drawing operation to an arc-shaped wedge. However, I'm not getting the intended result after setting the clipping path to the canvas. For illustration, here is what I'm doing: ``` path.reset(); //Move to point #1 path.moveTo(rect.centerX(), rect.centerY()); //Per the documentation, this will draw a connecting line from the current //position to the starting position of the arc (at 0 degrees), add the arc //and my current position now lies at #2. path.arcTo(rect, 0, -30); //This should then close the path, finishing back at the center point (#3) path.close(); ``` This works, and when I simply draw this path (`canvas.drawPath(path, paint)`) it draws the wedge as shown above. However, when I set this path as the canvas's clipping path and draw into it: ``` //I've tried it with and without the Region.Op parameter canvas.clipPath(path, Region.Op.REPLACE); canvas.drawColor(Color.BLUE); ``` I get the following result instead (the wedge is left just to show reference): So it instead seems to clip to the bounding rect of the `Path`, and not the `Path` itself. Any ideas what's happening here? EDIT Just as an update, I've found a much more efficient way of doing this that allows for hardware acceleration. First, draw the entire image (that you'd be clipping) into an offscreen bitmap. Make a `BitmapShader` using this `Bitmap`, set that shader to a `Paint`, then draw the wedge path using that `Paint` object: ``` drawMyBitmap(bitmap); Shader shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP); Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); paint.setShader(shader); @Override public void onDraw(Canvas canvas) { canvas.drawArc(rect, //The rectangle bounding the circle startAngle, //The angle (CW from 3 o'clock) to start sweepAngle, //The angle (CW from 3 o'clock) of the arc true, //Boolean of whether to draw a filled arc (wedge) paint //The paint with the shader attached ); } ```