android - 根据矩阵将触摸值转换为点

Question

我正在按矩阵平移和缩放图像，现在我有了矩阵值。所以从矩阵值我想将我的触摸坐标转换为它的位置，这是通过矩阵获得的。那我该怎么做呢？请尽快帮助我。

private void drawPoint(float x, float y, float pressure, float width) {

 // left is tx of matrix 
     // top is ty of matrix

    float curX = (x - left) / (scale * scale);
    float curY = (y - top) / (scale * scale);

         canvas.drawPoint((curX - left), (curY - top) , mPaint);
}

Answer 1

我知道这是一篇旧帖子，但我遇到了同样的问题。

我有一张应用了矩阵变换的图像，首先调整它的大小，然后进行平移。

    image = new Matrix();
    image.setScale(zoom, zoom);

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

    float centerScaledWidth = image_center.x * zoom / 2;
    float centerScaledHeigth = image_center.y * zoom / 2;

    image.postTranslate(screen_center.x -  centerScaledWidth, 
            screen_center.y - centerScaledHeigth);

    canvas.drawBitmap(bmp, image, drawPaint);

为了得到图像上的点，我得到了矩阵 image 的踪迹，这是方法:

    @Override
    public boolean onTouchEvent(MotionEvent ev) {

            final int action = ev.getAction();

            switch (action & MotionEvent.ACTION_MASK) {

                    case MotionEvent.ACTION_DOWN: {

                        final float x = ev.getX();
                        final float y = ev.getY();

                        float[] pts = {x, y};

                        Matrix m = new Matrix();

                        // This is the magic, I set the new matrix m 
                        // as the inverse of 
                        // the matrix applied to the image
                        image.invert(m);

                        // transform the points using the inverse matrix
                        m.mapPoints(pts);

                        // do what you have to do
                        .......

                        Log.i("transformed", pts[0] +" "+pts[1]);

                        break;
                    }

            }

    return super.onTouchEvent(ev);
}