如何在 C# windows 窗体中绘制可缩放图像

Question

所以我正在实施一个项目，可以读取图像平移、缩放和做其他事情..一切都很顺利，直到我尝试用鼠标右键实施绘图。

问题是当我画一条线时，图像上出现的线与我在屏幕上画的线不对应，这意味着它发生了偏移，我知道它是因为图像的大小调整和缩放，但是当我在图像上以其原始大小（图像）和平移画线时；我没问题。

这是代码。

所以首先这里是我如何在单击浏览和 select 图像

时加载图像

Myimage = new Bitmap(ImagePath);
resized = myImage.Size;
imageResize();
pictureBox.Paint += new    System.Windows.Forms.PaintEventHandler(this.pictureBox_Paint);
                pictureBox.Invalidate();

imageResize 函数执行以下操作：

void imageResize()
{     
//calculated the size to fit the control i will draw the image on   
 resized.Height = someMath;
 resized.Width = someMath;
}

然后在 pictureBox_Paint 事件的事件处理程序中我写道：

private void pictureBox_Paint(object sender,      System.Windows.Forms.PaintEventArgs e)
{
// Create a local version of the graphics object for the PictureBox.
Graphics PboxGraphics = e.Graphics;
PboxGraphics.DrawImage(myImage, imageULcorner.X, imageULcorner.Y,     resized.Width, resized.Height);
}

如您所见，调整后的尺寸不是原始图像尺寸，我这样做是因为我希望图像显示在集中的图片框控件上并填充现在下一部分是我的问题开始的地方

我必须使用鼠标右键在图像上画线，所以我实现了 pictureBox_MouseDown & pictureBox_MouseUp 事件处理程序

// mouse down event handler
private void pictureBox_MouseDown(object sender, MouseEventArgs e)
{
else if (mouse.Button == MouseButtons.Right)
{
mouseDown = mouse.Location;
mouseDown.X = mouseDown.X - imageULcorner.X;
mouseDown.Y = mouseDown.Y - imageULcorner.Y;
draw = true;
}
}

这里是鼠标弹起事件处理程序

//Mouse UP
private void pictureBox_MouseUp(object sender, MouseEventArgs e)
{
else if (mouse.Button == MouseButtons.Right)
{
if (draw)
 {
mouseLocationNow.X = mouse.X - imageULcorner.X;
mouseLocationNow.Y = mouse.Y - imageULcorner.Y;
//
// get graphics object of the image ( the original not the resized)
// as the resized image only appears when i draw on the graphics of the
// pictureBox control
// i know the problem lies here but how can i fix it
//
Graphics image = Graphics.FromImage(myImage);
Pen pen = new Pen(Color.Red, 2);
image.DrawLine(pen, mouseLocationNow, mouseDown);
pictureBox.Invalidate();
}
draw = false;
}

所以最后我希望能够在重新调整大小的图像上绘制并使其与真实图像以及我画线的屏幕相对应感谢和抱歉这么久 post 但这个问题一直让我抓狂。

Answer 1

这是一个 PictureBox 子类，它不仅支持对 Image 应用缩放功能，而且还支持在其表面上绘制的图形应用缩放功能。

它包含一个 SetZoom 功能，可通过缩放自身和矩阵来放大。

它还有一个 ScalePoint 函数，您可以使用它根据您在鼠标事件中收到的像素坐标计算未缩放的坐标。

想法是使用 Transformation Matrix 缩放 Graphics 对象将在 Paint 事件中绘制的任何像素。

我在表单中添加了一些代码用于测试。

public partial class ScaledPictureBox : PictureBox
{
    public Matrix ScaleM { get; set; }

    float Zoom { get; set; }
    Size ImgSize { get; set; }

    public ScaledPictureBox()
    {
        InitializeComponent();
        ScaleM = new Matrix();
        SizeMode = PictureBoxSizeMode.Zoom;
    }

    public void InitImage()
    {
        if (Image != null)
        {
            ImgSize = Image.Size;
            Size = ImgSize;
            SetZoom(100);
        }
    }

    public void SetZoom(float zoomfactor)
    {
        if (zoomfactor <= 0) throw new Exception("Zoom must be positive");
        float oldZoom = Zoom;
        Zoom = zoomfactor / 100f;
        ScaleM.Reset();
        ScaleM.Scale(Zoom , Zoom );
        if (ImgSize != Size.Empty) Size = new Size((int)(ImgSize.Width * Zoom), 
                                                   (int)(ImgSize.Height * Zoom));

    }

    public PointF ScalePoint(PointF pt)
    {   return new PointF(pt.X / Zoom , pt.Y / Zoom );     }

}

这是执行测试的表单中的代码：

public List<PointF> somePoints = new List<PointF>();

private void scaledPictureBox1_MouseClick(object sender, MouseEventArgs e)
{
    somePoints.Add(scaledPictureBox1.ScalePoint(e.Location) );
    scaledPictureBox1.Invalidate();
}

private void scaledPictureBox1_Paint(object sender, PaintEventArgs e)
{
    // here we apply the scaling matrix to the graphics object:
    e.Graphics.MultiplyTransform(scaledPictureBox1.ScaleM);
    using (Pen pen = new Pen(Color.Red, 10f))
    {
        PointF center = new PointF(scaledPictureBox1.Width / 2f, 
                                   scaledPictureBox1.Height / 2f);
        center = scaledPictureBox1.ScalePoint(center);
        foreach (PointF pt in somePoints)
        {
            DrawPoint(e.Graphics, pt, pen);
            e.Graphics.DrawLine(Pens.Yellow, center, pt);
        }
    }
}

public void DrawPoint(Graphics G, PointF pt, Pen pen)
{
    using (SolidBrush brush = new SolidBrush(pen.Color))
    {
        float pw = pen.Width;
        float pr = pw / 2f;
        G.FillEllipse(brush, new RectangleF(pt.X - pr, pt.Y - pr, pw, pw));
    }
}

以下是绘制几个点后的结果，显示了四种不同缩放设置下的相同点； ScaledPictureBox 显然放在 AutoScroll-Panel 中。这些线条显示了如何使用常规绘图命令..

如何在 C# windows 窗体中绘制可缩放图像

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