我有一个ImageView
子类,用于绘制带圆角的图片。 该代码基于此答案,如下所示:
public class ImageViewRoundedCorners extends ImageView {
...
@Override
protected void onDraw(Canvas canvas) {
Bitmap scaledBitmap = Bitmap.createBitmap(getMeasuredWidth(),
getMeasuredHeight(),
Bitmap.Config.ARGB_8888);
Canvas scaledCanvas = new Canvas(scaledBitmap);
super.onDraw(scaledCanvas);
drawRoundedCornerBitmap(canvas, scaledBitmap,
getMeasuredWidth(), getMeasuredHeight());
scaledBitmap.recycle();
}
protected void drawRoundedCornerBitmap(Canvas outputCanvas, Bitmap input, int w, int h) {
Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);
Canvas canvas = new Canvas(output);
mPaint.reset();
mPaint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
mPaint.setStyle(Paint.Style.FILL);
canvas.drawPath(mClipPath, mPaint);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(input, 0, 0, mPaint);
outputCanvas.drawBitmap(output, 0, 0, null);
}
}
使用这段代码可以绘制带有正确圆角的图像。为了避免在
drawRoundedCornerBitmap
的前两行中进行分配,我想直接绘制到outputCanvas
上,该画布最初传递给onDraw
。新实现如下所示:protected void drawRoundedCornerBitmap(...) {
mPaint.reset();
mPaint.setAntiAlias(true);
outputCanvas.drawARGB(0, 0, 0, 0);
mPaint.setStyle(Paint.Style.FILL);
outputCanvas.drawPath(mClipPath, mPaint);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
outputCanvas.drawBitmap(input, 0, 0, mPaint);
}
由于某种原因,该代码似乎忽略了Porter-Duff模式,而只是使用普通(非圆角)角绘制图像。为什么会这样?在一个中间的Bitmap
上绘制有什么作用可以让原始代码正常工作?