Android drawMatrix转换位图后如何取回原始坐标

Question

我有以下问题。我有一个位图，在这个位图上可以完成某些绘制操作。比如画线、箭头等等

效果很好，但位图可以缩放、拖动和旋转。为此，使用了 drawMatrix。这一切都很好，但是，为了绘图，我需要原始坐标，以便绘图大小合适，等等。

我可以用下面的函数得到这个原始坐标。但它不适用于轮换。有没有人知道如何解决这个问题？

    /**
     * When we have moved or zoomed we need the original image coordinates calculated from
     * the screen coordinates. This function gives that back
     */
    private Point translateScreenCoordsToOriginalImageCoords(MotionEvent e) {
        float[] m = new float[9];
        drawMatrix.getValues(m);

        float transX = m[Matrix.MTRANS_X] * -1;
        float transY = m[Matrix.MTRANS_Y] * -1;
        float scaleX = m[Matrix.MSCALE_X];
        float scaleY = m[Matrix.MSCALE_Y];

        // TODO function does not work when rotated by 90 degree
        if (scaleX == 0.0) {
            scaleX = -1.0f;
            scaleY = -1.0f;
        }

        int lastTouchX = (int) ((e.getX() + transX) / scaleX);
        int lastTouchY = (int) ((e.getY() + transY) / scaleY);
        lastTouchX = Math.abs(lastTouchX);
        lastTouchY = Math.abs(lastTouchY);

        return new Point(lastTouchX, lastTouchY);
    }

缩放是这样进行的

/**
 * Scale the canvas by
 *
 * @param scaleFactor e.g 2 is double
 * @param focusX      the center x point
 * @param focusY      the center y point
 *
 * @return true if scaling is performed
 */
private boolean doScale(float scaleFactor, int focusX, int focusY) {
    if (this.scaleBoundaries(scaleFactor))
        return false;

    Matrix transformationMatrix = new Matrix();

    // Zoom focus is where the fingers are centered
    transformationMatrix.postTranslate(-focusX, -focusY);
    transformationMatrix.postScale(scaleFactor, scaleFactor);

    transformationMatrix.postTranslate(focusX, focusY);
    drawMatrix.postConcat(transformationMatrix);

    invalidate();

    return true;
}

例如这是 Line

的绘制函数

@Override
public void draw(Canvas c, Matrix drawMatrix, boolean translateCoordiantes) {
    float pts[] = new float[] {this.start.x, this.start.y, this.end.x, this.end.y};

    if (translateCoordiantes)
        drawMatrix.mapPoints(pts);

    c.drawLine(pts[0], pts[1], pts[2], pts[3], this.paint);
}

Answer 1

哇 pskink 非常感谢！这就是答案！要取回原始坐标，请使用：

private Point translateCoordinatesBack(MotionEvent event) {
        Matrix inverse = new Matrix();

        drawMatrix.invert(inverse);

        float[] pts = {event.getX(), event.getY()};
        inverse.mapPoints(pts);

        return new Point((int) pts[0], (int) pts[1]);
}

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