图形以 c# windows 形式绘制不正确

Question

如何确保我的图形绘制在正确的位置？我有一个 windows 表单项目，用户在 pictureBox（面板顶部）中的图像上绘制线条。当图片框处于默认缩放状态时，线条会正确绘制，并且它们会正确响应图像参差不齐的情况。但是，当我尝试在缩放 in/out 时在图像上绘制时，线条的位置发生了偏移（缩小时向上和向左，放大时向下和向右）。 pictureBox 和面板都固定在所有四个边上，而不是停靠。我尝试使用 TranslateTransform( dx, dy ) 方法，但它没有用。我也尝试摆脱我的 CenterBox() 方法。我该如何进行？

这里是缩放代码：

private void trackBar1_Scroll(object sender, EventArgs e)  // zoom scale
{
    zoom = (float)(0.25 + 0.25 * (trackBar1.Value - 1));
    if (trackBar1.Value > 0)
    {
        pictureBox1.Image = PictureBoxZoom(imgOriginal, new Size(trackBar1.Value, trackBar1.Value));
    }

}

public Image PictureBoxZoom(Image img, Size size) //creates zoomed in clone of user image
{
    sizeNewx = (Int32) (img.Width * zoom);
    sizeNewy = (Int32) (img.Height * zoom);
    Bitmap bm = new Bitmap(img, sizeNewx,sizeNewy);
    Graphics grap = Graphics.FromImage(bm);
    grap.InterpolationMode = InterpolationMode.HighQualityBicubic;
    CenterBox(pictureBox1, bm);
    return bm;
}

private void CenterBox(PictureBox picBox, Bitmap pic)
{
    picBox.Image = pic;
    picBox.Location = new Point((picBox.Parent.ClientSize.Width / 2) - (pic.Width / 2),
                       (picBox.Parent.ClientSize.Height / 2) - (pic.Height / 2));
    picBox.Refresh();
}

图形的绘制和缩放方式如下：

private Stack<Line> lines = new Stack<Line>();

private void pictureBox1_MouseDown(object sender, MouseEventArgs e) //click in box
{
    var mouseEventArgs2 = e as MouseEventArgs;

    if (e.Button == MouseButtons.Left)
    {        
        lines.Push(new Line { Start = mouseEventArgs2.Location });
    }
}

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{       
    if (lines.Count > 0 && e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        lines.Peek().End = e.Location;
        pictureBox1.Invalidate();
    }
}

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.ScaleTransform(zoom, zoom);

    foreach (var line in lines)
    {
        Pen magenta = new Pen(Color.Magenta, 2);
        e.Graphics.DrawLine(magenta, line.Start, line.End);
    }
}

Answer 1

好的，找到问题了。问题是你在 mouse move 和 mouse end 中得到的点基本上是 缩放的 ，因为图像被缩放，然后在绘画中你再次缩放它们。所以你需要 un scale them before paint:

private void pictureBox1_MouseDown(object sender, MouseEventArgs e) //click in box
{
    var mouseEventArgs2 = e as MouseEventArgs;

    if (e.Button == MouseButtons.Left)
    {        
        Point[] pnts = new Point[ 1 ];
        Matrix scaleMatrix = new Matrix( 1 / zoom, 0, 0, 1 / zoom, 0, 0 ); //un scale
        pnts[0]= mouseEventArgs2.Location;
        scaleMatrix.TransformPoints( pnts );

        lines.Push(new Line { Start = pnts[0] });
    }
}

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{       
    if (lines.Count > 0 && e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        Point[] pnts = new Point[ 1 ];
        Matrix scaleMatrix = new Matrix( 1 / zoom, 0, 0, 1 / zoom, 0, 0 ); //un scale
        pnts[0]= e.Location;
        scaleMatrix.TransformPoints( pnts );

        lines.Peek().End = pnts[0];
        pictureBox1.Invalidate();
    }
 }

图形以 c# windows 形式绘制不正确

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