在 dispatchDraw 中交换 Android ViewGroup Child 颜色

Question

我有一个 ViewGroup（特别是 FrameLayout），它应该有一个流体填充效果，我用一条路径动画，很好地显示下面的 child 视图。

问题是在液体填充线上方我需要显示 children 并且视图的两种颜色颠倒。（黑色<->白色）如果不简单地遍历位图，我看不到实现此目的的方法，它提供的副本非常差，有很多锯齿，而且渲染速度太慢。

这是我当前在 dispatchDraw 中的功能的简化版本：

@Override
protected void dispatchDraw(Canvas canvas)
{
    filter.setXfermode(null);
    if (subBitmap == null || mLastWidth != mWidth) {
        subBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        subCanvas = new Canvas(subBitmap);
    }
    super.dispatchDraw(subCanvas);
    if (mLiquidPaint == null || mLiquidPath == null || waveOval.size() == 0 || bitmapPixels == null || !mLiquidAnimator.isRunning()) {
        canvas.drawBitmap(subBitmap, 0, 0, filter);
        return;
    }

    if (revealBitmap == null || mLastWidth != mWidth) {
        revealBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        revealCanvas = new Canvas(revealBitmap);
    }
    if (mLastWidth != mWidth) {
        calculateLiquid();
        mLastWidth = mWidth;
    }
    int yOffset = mFillOffset;
    int xOffset = ellipseWidth * -1;
    PointF firstPoint = new PointF();
    PointF lastPoint = new PointF();
    PointF nextPoint = new PointF();
    Pair<Integer, Float> nextWavePoint = wavePoints.get(0);
    PointF ovalPoint = waveOval.get((nextWavePoint.first + mWaveOffset) % waveOval.size());
    lastPoint.set(xOffset + nextWavePoint.second + ovalPoint.x, yOffset + ovalPoint.y);
    mLiquidPath.moveTo(lastPoint.x, lastPoint.y);
    firstPoint.set(lastPoint);
    for (int i = 1; i < wavePoints.size(); i++) {
        nextWavePoint = wavePoints.get(i);
        ovalPoint = waveOval.get((nextWavePoint.first + mWaveOffset) % waveOval.size());
        nextPoint.set(xOffset + nextWavePoint.second + ovalPoint.x, ovalPoint.y + yOffset);
        mLiquidPath.lineTo(nextPoint.x, nextPoint.y);
        lastPoint.set(nextPoint);
    }
    mLiquidPath.lineTo(getWidth(), lastPoint.y);
    mLiquidPath.lineTo(getWidth(), getHeight());
    mLiquidPath.lineTo(0, getHeight());
    mLiquidPath.lineTo(firstPoint.x, firstPoint.y);

    //This definitely draws a nice liquid path that fills from the bottom up.
    revealCanvas.drawPath(mLiquidPath, mLiquidPaint);
    //The next two lines successfully reveal the views underneath
    filter.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP));
    revealCanvas.drawBitmap(subBitmap, 0, 0, filter);

    filter.setXfermode(null);
    filter.setColorFilter(null);
    canvas.drawBitmap(revealBitmap, 0, 0, filter);
}

我尝试了无数种不同的 ColorFilters 和传输模式，但都无济于事。而且 children 不能让背景透明让我做更简单的颜色替换。

Answer 1

最终使用 ColorMatrixColorFilter 解决了这个问题，如下所述：

对于两种颜色 color1 和 color2，您将它们与以下 ColorMatrix 交换：

float[] colorSwapMatrix = new float[] {
    -1, 0, 0, 0, Color.red(color1) + Color.red(color2),    //Red
    0, -1, 0, 0, Color.green(color1) + Color.green(color2),//Green
    0, 0, -1, 0, Color.blue(color1) + Color.blue(color2),  //Blue
    0, 0, 0, 1f, 0                                         //Alpha
}

这是在绘制上面的波路径后应用的，如下所示：

    //Draw the swapped image above the wave
    filter.setColorFilter(new ColorMatrixColorFilter(colorSwapMatrix));
    filter.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT));
    revealCanvas.drawBitmap(subBitmap, 0, 0, filter);

    //Draw the regular image below the wave
    filter.setColorFilter(null);
    filter.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_ATOP));
    revealCanvas.drawBitmap(subBitmap, 0, 0, filter);

    //Draw the combined image onto the canvas
    filter.setXfermode(null);
    filter.setColorFilter(null);
    canvas.drawBitmap(revealBitmap, 0, 0, filter);

在 dispatchDraw 中交换 Android ViewGroup Child 颜色

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