Canvas clipping limits the drawing region: only content within the clipped area is visible.

Region.Op Clip Modes

Canvas supports combining multiple clip regions through Region.Op:

Enum ValueDescription
DIFFERENCE(0)Final region is the part of region1 NOT in region2
INTERSECT(1)Final region is the intersection of region1 and region2
UNION(2)Final region is the union of region1 and region2
XOR(3)Final region is the non-overlapping parts of region1 and region2
REVERSE_DIFFERENCE(4)Final region is the part of region2 NOT in region1
REPLACE(5)Final region is region2

Canvas05

Complete Example

The following code demonstrates the effect of each clip mode:

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private void drawScene(Canvas canvas) {
    canvas.clipRect(0, 0, 100 * factor, 100 * factor);

    canvas.drawColor(Color.WHITE);

    mPaint.setColor(Color.RED);
    canvas.drawLine(0, 0, 100 * factor, 100 * factor, mPaint);

    mPaint.setColor(Color.GREEN);
    canvas.drawCircle(30 * factor, 70 * factor, 30 * factor, mPaint);

    mPaint.setColor(Color.BLUE);
    canvas.drawText("Clipping", 100 * factor, 30 * factor, mPaint);
}

@Override
protected void onDraw(Canvas canvas) {

    canvas.drawColor(Color.GRAY);

    canvas.save();
    canvas.translate(10 * factor, 10 * factor);
    drawScene(canvas);
    canvas.restore();

    canvas.save();
    canvas.translate(160 * factor, 10 * factor);
    canvas.clipRect(10 * factor, 10 * factor, 90 * factor, 90 * factor);
    canvas.clipRect(30 * factor, 30 * factor, 70 * factor, 70 * factor, Region.Op.DIFFERENCE);
    drawScene(canvas);
    canvas.restore();

    canvas.save();
    canvas.translate(10 * factor, 160 * factor);
    mPath.reset();
    mPath.addCircle(50 * factor, 50 * factor, 50 * factor, Path.Direction.CCW);
    canvas.clipPath(mPath, Region.Op.REPLACE);
    drawScene(canvas);
    canvas.restore();

    canvas.save();
    canvas.translate(160 * factor, 160 * factor);
    canvas.clipRect(0, 0, 60 * factor, 60 * factor);
    canvas.clipRect(40 * factor, 40 * factor, 100 * factor, 100 * factor, Region.Op.UNION);
    drawScene(canvas);
    canvas.restore();

    canvas.save();
    canvas.translate(10 * factor, 310 * factor);
    canvas.clipRect(0, 0, 60 * factor, 60 * factor);
    canvas.clipRect(40 * factor, 40 * factor, 100 * factor, 100 * factor, Region.Op.XOR);
    drawScene(canvas);
    canvas.restore();

    canvas.save();
    canvas.translate(160 * factor, 310 * factor);
    canvas.clipRect(0, 0, 60 * factor, 60 * factor);
    canvas.clipRect(40 * factor, 40 * factor, 100 * factor, 100 * factor,
            Region.Op.REVERSE_DIFFERENCE);
    drawScene(canvas);
    canvas.restore();
}

Using canvas.save() and canvas.restore() preserves and restores the Canvas state, ensuring each clip operation only affects the current drawing scope.

References