在图片框内绘制矩形 SizeMode Zoom

Question

我在 WindowsForms 项目中有一个图片框，其 SizeMode 为 "Zoom"。

我想在图像中绘制一个矩形并获取其相对于图像而不是图片框的坐标。

问题是矩形的坐标与在 Windows 绘画应用程序中选择的相同矩形不匹配。

这里是使用的代码：

开始绘画：

/// <summary>
/// Starts drawing.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    backupImage = pictureBox1.Image;
    _once = true;
    RectStartPoint = e.Location;
    pictureBox1.Invalidate();
}

移动鼠标时：

/// <summary>
/// While moving mouse event, paint rectangle
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if (_once) //Only draw rectangle while drawing mode
    {
        Point tempEndPoint = e.Location;
        Rect.Location = new Point(Math.Min(RectStartPoint.X, tempEndPoint.X),
            Math.Min(RectStartPoint.Y, tempEndPoint.Y));

        Rect = new Rectangle(
            Math.Min(tempEndPoint.X, Rect.Left),
            Math.Min(tempEndPoint.Y, Rect.Top),
            Math.Min(e.X - RectStartPoint.X, pictureBox1.ClientRectangle.Width - RectStartPoint.X),
            Math.Min(e.Y - RectStartPoint.Y, pictureBox1.ClientRectangle.Height - RectStartPoint.Y));

        pictureBox1.Refresh();
        pictureBox1.CreateGraphics().DrawRectangle(cropPen, Rect);
    }
}

点击2次，完成绘制矩形：

/// <summary>
/// When mouse click is released, write in texbox the rectangle's coordinates.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
    if (_once)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            Point tempEndPoint = e.Location;

            _once = false;
            string sAux = string.Format("Left: {0}; Top: {1}; Width: {2}; Height: {3} \r\n", Math.Min(tempEndPoint.X, Rect.Left), Math.Min(tempEndPoint.Y, Rect.Top),
                    Math.Min(e.X - RectStartPoint.X, pictureBox1.ClientRectangle.Width - RectStartPoint.X), Math.Min(e.Y - RectStartPoint.Y, pictureBox1.ClientRectangle.Height - RectStartPoint.Y));

            textBox1.Text += sAux;
        }
    }
}

结果是：

Windows 图片

绘制图像

如您在两张图片中所见，左侧、顶部、宽度和高度不匹配。

你能告诉我如何获得相同的结果吗？

Example2

Answer 1

这里有一个函数可以帮助进行各种计算：

void SetImageScale(PictureBox pbox, out RectangleF ImgArea, out float zoom)
{
    SizeF sp = pbox.ClientSize;
    SizeF si = pbox.Image.Size;
    float rp = sp.Width / sp.Height;   // calculate the ratios of
    float ri = si.Width / si.Height;   // pbox and image

    if (rp > ri)
    {
        zoom = 1f * sp.Height / si.Height;
        float width = si.Width * zoom;
        float left = (sp.Width - width) / 2;
        ImgArea = new RectangleF(left, 0, width, sp.Height);
    }
    else
    {
        zoom = 1f * sp.Width / si.Width;
        float height = si.Height * zoom;
        float top = (sp.Height - height) / 2;
        ImgArea = new RectangleF(0, top, sp.Width, height);
    }
}

这里是你如何使用它，给定一个你从鼠标坐标创建的 Rectangle Rect：

float zoom = 1f;
RectangleF ImgArea = Rectangle.Empty;

SetImageScale(pictureBox1, out ImgArea, out zoom);

Point RLoc = Point.Round(new PointF( (Rect.X - ImgArea.X) / zoom, 
                                     (Rect.Y - ImgArea.Y) / zoom ));
Size RSz = Size.Round(new SizeF(Rect.Width / zoom, Rect.Height / zoom));

label1.Text =  "Selection in mouse coordinates: "  + Rect.ToString();
label2.Text =  "Selection in image coordinates: "  + new Rectangle(RLoc, RSz).ToString();

无论图像是横向的还是纵向的，或者图像的比例还是 PictureBox 的比例更大，这都应该有效。

请注意，随着图像的强烈缩放，很难进行像素完美的选择。

该函数是中函数的变体。

在图片框内绘制矩形 SizeMode Zoom

Draw Rectangle inside picture box SizeMode Zoom

c#

picturebox

zooming

winforms