Question

我需要将ImageView旋转几度。我是通过继承ImageView并重载onDraw()

来做到这一点的

@Override
protected void onDraw(Canvas canvas) {
    canvas.save();
    canvas.scale(0.92f,0.92f);
    canvas.translate(14, 0);
    canvas.rotate(1,0,0);
    super.onDraw(canvas);
    canvas.restore();
}

问题是结果的图像显示出一堆锯齿状。

http://img.skitch.com/20100608-gmdy4sexsm1c71di9rgiktdjhu.png

我如何消除我需要旋转的ImageView才能消除锯齿？有更好的方法吗？

Answer 1

如果您知道您的Drawable是BitmapDrawable，您可以在位图的Paint中使用消除锯齿来执行以下操作：

/**
 * Not as full featured as ImageView.onDraw().  Does not handle 
 * drawables other than BitmapDrawable, crop to padding, or other adjustments.
 */
@Override
protected void onDraw(Canvas canvas) {
    final Drawable d = getDrawable();

    if( d!=null && d instanceof BitmapDrawable && ((BitmapDrawable)d).getBitmap()!=null ) {
        final Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
        final int paddingLeft = getPaddingLeft();
        final int paddingTop = getPaddingTop();

        canvas.save();

        // do my rotation and other adjustments
        canvas.scale(0.92f,0.92f);
        canvas.rotate(1,0,0);

        if( paddingLeft!=0 )
            canvas.translate(paddingLeft,0);

        if( paddingTop!=0 )
            canvas.translate(0,paddingTop);

        canvas.drawBitmap( ((BitmapDrawable)d).getBitmap(),0,0,p );
        canvas.restore();
    }
}

Answer 2

将antialias和filterBitmap设置为绘制位图的绘画。我有类似的问题，这对我有用：

Paint bitmapPaint = new Paint();
bitmapPaint.setAntiAlias(true);
bitmapPaint.setFilterBitmap(true);

Answer 3

我做了以下工作让它发挥作用：

在AndroidManifest.xml我启用了硬件加速<application android:hardwareAccelerated="true">。

我没有使用自定义绘图方法，而是将父视图的图层类型更改为硬件加速并启用了抗锯齿，并添加了我的子视图，如下所示：

Paint layerPaint =  new Paint();
layerPaint.setAntiAlias(true);
layerPaint.setFilterBitmap(true);
layerPaint.setDither(true);

RelativeLayout parentLayout = (RelativeLayout) LayoutInflater.from(context).inflate(R.layout.myLayout, null);
parentLayout.setLayerType(View.LAYER_TYPE_HARDWARE, layerPaint);

parentLayout.addView(myChildView);

我必须补充一点，使用这种方法时无法禁用裁剪。

Answer 4

这种旋转只能解决问题的一部分 - 锯齿状边缘，但图像反而变得奇怪。

ifound只有一个解决方案：在提取或派遣抽签方法

        Bitmap bmp = ((BitmapDrawable)image.getDrawable()).getBitmap();
    double scale = (0.0+bmp.getWidth()+40.0)/getWidth();
    if (scale > 1){
        bmp = Bitmap.createScaledBitmap(bmp, getWidth()-40, (int) (bmp.getHeight()/scale), true);
    }

    canvas.drawColor(Color.TRANSPARENT); 
    canvas.save();

    canvas.translate(20, yShift);

    int left = borderSize;
    int top = borderSize;
    int right = bmp.getWidth() - borderSize;
    int bottom = bmp.getHeight() - borderSize;

    if(showText){
        mPaint.setColor(Color.WHITE);
        canvas.rotate(getAngel());
        canvas.drawRect(left, top, right, bottom, mPaint);

        canvas.translate(0,0);
        textFrame.draw(canvas);
    }else{
        // rotaed bitmap 
        mMatrix.setRotate(getAngel());

        // draw bitmap after creation of new rotated bitmap from rotated matrix
        canvas.drawBitmap(Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), mMatrix, true)
                   , 0, 0, mPaint);
    }
    canvas.restore();

Answer 5

@Primoz990的解决方案对我有用:)我也启用了抖动，所以我的最终代码可以消除旋转时的锯齿状边缘：

Paint bitmapPaint =  new Paint();
bitmapPaint.setAntiAlias(true);
bitmapPaint.setFilterBitmap(true);
bitmapPaint.setDither(true);

如何在启用了抗锯齿的情况下旋转drawable

5 个答案: