如何在使用画布上的绘制路径绘制的路径内裁剪图像，Android

Question

我可以在Canvas 上使用moveTo() 和lineTo() 命令绘制一个矩形。我现在要做的是裁剪位于这个正方形内的位图。

这是我的onDraw() 方法：

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    drawPath.moveTo(topLeft.x, topLeft.y);
    drawPath.lineTo(topRight.x, topRight.y);
    drawPath.lineTo(bottomRight.x, bottomRight.y);
    drawPath.lineTo(bottomLeft.x, bottomLeft.y);
    drawPath.lineTo(topLeft.x, topLeft.y);
    drawCanvas = new Canvas(canvasBitmap);
    canvas.drawPath(drawPath, drawPaint);
    canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
}

Answer 1

试试这个：

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    drawPath.moveTo(topLeft.x, topLeft.y);
    drawPath.lineTo(topRight.x, topRight.y);
    drawPath.lineTo(bottomRight.x, bottomRight.y);
    drawPath.lineTo(bottomLeft.x, bottomLeft.y);
    drawPath.lineTo(topLeft.x, topLeft.y);
    canvas.clipPath(drawPath);
    canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
}

如果drawPath 始终是一个矩形，您可以使用Canvas.clipRect()。这是使用clipRect()重写的相同代码：

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.clipRect(left, top, right, bottom);
    canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
}