如何获得图像位置？

Question

这是pictureBox1的paint事件中的代码。 我需要找到变量mImage的位置。

if (null != mImage)
{
    e.Graphics.DrawImage(mImage, theLocationOfImage);
}

mImage是图像类型。 相反，我需要放置mImage的位置。 这就是我得到mImage的方式：

private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
{
    Bitmap bmp = new Bitmap(pictureBox1.Image);
    Bitmap bmp1 = GetPartOfImageInRect(bmp, mRect);
    CalculateNewSizeFactor(e.Delta);
    Image img1 = ResizeImage(bmp1, 
        new Size((int)(bmp1.Width * currentfactor), 
           (int)(bmp1.Height * currentfactor)));
    mImage = img1;

    pictureBox1.Invalidate();
}

mRect是我在pictureBox1上绘制的矩形。

编辑

这是我绘制矩形的方式：

private void DrawRectangle(Graphics e)
        {
            using (Pen pen = new Pen(Color.Red, 2))
            {
                e.DrawRectangle(pen, mRect);
            }
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            mRect = new Rectangle(e.X, e.Y, 0, 0);
            pictureBox1.Invalidate();
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mRect = new Rectangle(mRect.Left, mRect.Top, e.X - mRect.Left, e.Y - mRect.Top);
                pictureBox1.Invalidate();
            }
        }

这是调整大小图像方法：

private Image ResizeImage(Image img, Size size)
        {
            return new Bitmap(img, size);
        }

这是pictureBox1绘画事件：

if (null != mImage)
            {
                e.Graphics.DrawImage(mImage, theLocationOfImage);
            }
            DrawRectangle(e.Graphics);

最后计算新的尺寸系数方法：

private void CalculateNewSizeFactor(int delta)
        {
            if (delta > 0 && factor < 2.5)
            {
                factor *= increment;
                currentfactor = factor;
            }
            else if (delta < 0 && factor > 0.25)
            {
                factor /= increment;
                currentfactor = factor;
            }
        }

我可以调整放大整个图像的大小，但是我只想缩小绘制矩形的区域。

编辑

忘记添加此方法：

private Bitmap GetPartOfImageInRect(Bitmap source, Rectangle rect)
        {
            return source.Clone(rect, source.PixelFormat);
        }

Answer 1

缩放时的问题是要缩放的矩形的纵横比可能与整个图像的纵横比不同。 因此，您必须考虑两种不同的情况。

// Calculate the size and position of the zoomed rectangle.
double zoomFactorX = picturBox1.Width / mRect.Width;
double zoomFactorY = picturBox1.Height / mRect.Height;
Size newSize;
Point newLocation;
if (zoomFactorX < zoomFactorY) { // Fit image portion horizontally.
    newSize = new Size(picturBox1.Width, (int)Math.Round(zoomFactorX * mRect.Height));

    // We have a top and a bottom padding.
    newLocation = new Point(0, (picturBox1.Height - newSize.Height) / 2);
} else {  // Fit image portion vertically.
    newSize = new Size((int)Math.Round(zoomFactorY * mRect.Width), picturBox1.Height);

    // We have a left and a right padding.
    newLocation = new Point((picturBox1.Width - newSize.Width) / 2, 0);
}