C# 用C语言缩放图像#

我在缩放图像时遇到问题。我已成功缩放图像，但图像在上下滚动时会中断

public partial class ImageDetail : UserControl
{
    public delegate void onClose();
    public event onClose close;
    Image pbImage;
    public ImageDetail(Image img)
    {            
        InitializeComponent();
        pictureBox.Image = img;
        pbImage = img;
        pictureBox.Width = this.pbImage.Width;
        pictureBox.Height = this.pbImage.Height;
        panel2.AutoScroll = true;
        panel2.HorizontalScroll.Maximum = img.Width;
        panel2.VerticalScroll.Maximum   = img.Height;
        panel2.HorizontalScroll.Minimum = 0;
        panel2.VerticalScroll.Minimum   = 0;
        panel2.SetAutoScrollMargin(10, 10);            
    }

    private void label2_Click(object sender, EventArgs e)
    {
        if (close != null)
            close(); 
    }        

    private void DrawImage(int startX, int startY)
    {            
        if (this.pbImage == null) { return; }

        Graphics pbGraphics = this.pictureBox.CreateGraphics();
        BufferedGraphicsContext currentGraphicsContext = BufferedGraphicsManager.Current;
        Rectangle targetRect = new Rectangle(startX, startY, (this.pbImage.Width + tmpWidth), (this.pbImage.Height + tmpHeight));
        using (BufferedGraphics pbGDIBuffer = currentGraphicsContext.Allocate(pbGraphics, targetRect))
        {
            Rectangle drawRect = new Rectangle(startX, startY, (this.pbImage.Width + tmpWidth), (this.pbImage.Height + tmpHeight));

            pbGDIBuffer.Graphics.DrawImageUnscaledAndClipped(this.pbImage, drawRect);
            pbGDIBuffer.Render();                
        }
        pictureBox.Width = this.pbImage.Width + tmpWidth;
        pictureBox.Height = this.pbImage.Height + tmpHeight;
    }             

    int tmpWidth = 0, tmpHeight = 0;
    private void toolStripSplitButton1_ButtonClick(object sender, EventArgs e)
    {
        tmpWidth = tmpWidth + ((this.pbImage.Width * 20) / 100);
        tmpHeight = tmpHeight + ((this.pbImage.Height * 20) / 100);

        pictureBox.Width = this.pbImage.Width + tmpWidth;
        pictureBox.Height = this.pbImage.Height + tmpHeight;
        pictureBox.Refresh();
        DrawImage(0, 0);
    }

    private void toolStripSplitButton2_ButtonClick(object sender, EventArgs e)
    {
        if(tmpWidth > 0)
            tmpWidth = tmpWidth - ((this.pbImage.Width * 20) / 100);
        if(tmpHeight > 0)
            tmpHeight = tmpHeight - ((this.pbImage.Height * 20) / 100);
        if (tmpHeight < 0)
            tmpHeight = 0;
        if (tmpWidth < 0)
            tmpWidth = 0;
        pictureBox.Refresh();
        DrawImage(0, 0);                      
    }

    private void panel2_MouseDown(object sender, MouseEventArgs e)
    {
        pictureBox.Width = this.pbImage.Width + tmpWidth;
        pictureBox.Height = this.pbImage.Height + tmpHeight;
    }

    private void panel2_MouseUp(object sender, MouseEventArgs e)
    {
        pictureBox.Width = this.pbImage.Width + tmpWidth;
        pictureBox.Height = this.pbImage.Height + tmpHeight;
    }

}

公共部分类ImageDetail:UserControl
{
公共委托void onClose（）；
公共事件关闭；
图像；
公共图像详细信息（图像img）
{            
初始化组件（）；
pictureBox.Image=img；
pbImage=img；
pictureBox.Width=this.pbImage.Width；
pictureBox.Height=this.pbImage.Height；
panel2.AutoScroll=true；
panel2.HorizontalScroll.Maximum=最小宽度；
面板2.VerticalScroll.Maximum=最小高度；
panel2.HorizontalScroll.Minimum=0；
panel2.VerticalScroll.Minimum=0；
面板2.设置自动滚动边距（10,10）；
}
私有无效标签2_单击（对象发送方，事件参数e）
{
如果（关闭！=null）
close（）；
}        
私有void DrawImage（int startX、int startY）
{            
如果（this.pbImage==null）{return；}
Graphics pbGraphics=this.pictureBox.CreateGraphics（）；
BufferedGraphicsContext currentGraphicsContext=BufferedGraphicsManager.Current；
矩形targetRect=新矩形（startX，startY，（this.pbImage.Width+tmpWidth），（this.pbImage.Height+tmpHeight））；
使用（BufferedGraphics pbGDIBuffer=currentGraphicsContext.Allocate（pbGraphics，targetRect））
{
矩形drawRect=新矩形（startX，startY，（this.pbImage.Width+tmpWidth），（this.pbImage.Height+tmpHeight））；
pbGDIBuffer.Graphics.DrawImageUnscaledClipped（this.pbImage，drawRect）；
pbGDIBuffer.Render（）；
}
pictureBox.Width=this.pbImage.Width+tmpWidth；
pictureBox.Height=this.pbImage.Height+tmpHeight；
}             
int tmpWidth=0，tmpHeight=0；
私有无效工具StripSplitButton1_按钮单击（对象发送方，事件参数e）
{
tmpWidth=tmpWidth+（（this.pbImage.Width*20）/100）；
tmpHeight=tmpHeight+（（this.pbImage.Height*20）/100）；
pictureBox.Width=this.pbImage.Width+tmpWidth；
pictureBox.Height=this.pbImage.Height+tmpHeight；
pictureBox.Refresh（）；
DrawImage（0,0）；
}
私有无效工具StripSplitButton2\u按钮单击（对象发送方，事件参数e）
{
如果（tmpWidth>0）
tmpWidth=tmpWidth-（（this.pbImage.Width*20）/100）；
如果（tmpHeight>0）
tmpHeight=tmpHeight-（（this.pbImage.Height*20）/100）；
如果（tmpHeight<0）
tmpHeight=0；
如果（tmpWidth<0）
tmpWidth=0；
pictureBox.Refresh（）；
DrawImage（0,0）；
}
专用无效面板2_鼠标向下（对象发送器，鼠标目标e）
{
pictureBox.Width=this.pbImage.Width+tmpWidth；
pictureBox.Height=this.pbImage.Height+tmpHeight；
}
专用无效面板2_鼠标（对象发送器，鼠标目标e）
{
pictureBox.Width=this.pbImage.Width+tmpWidth；
pictureBox.Height=this.pbImage.Height+tmpHeight；
}
}

您应该在事件上绘制图像（例如）：

调整调用方法的大小后：

---

您的代码应该是这样的：

public ImageDetail(Image img)
{
    pictureBox.Image = img;
    pbImage = img;
    ...
    pictureBox.Paint += pictureBox_Paint;
}

void pictureBox_Paint(object sender, PaintEventArgs e)
{
    if (pbImage == null) { return; }
    var drawRect = new Rectangle(startX, startY, pictureBox.Width, pictureBox.Height);
    e.Graphics.DrawImageUnscaledAndClipped(this.pbImage, drawRect);
}

private void toolStripSplitButton1_ButtonClick(object sender, EventArgs e)
{
    ///... resize to what you need 
    pictureBox.Width = (int) (pbImage.Width*0.2);
    pictureBox.Height = (int) (pbImage.Height * 0.2);
    pictureBox.Invalidate();
}

---

当您尝试滚动时，图像会发生什么变化？是否显示不正确？图像分为两个部分，每个部分都覆盖，顶部的图像是缩放的结果，底部的图像是具有初始大小的图像。当在图片上方滚动时慢慢擦除。

pictureBox.Invalidate();

public ImageDetail(Image img)
{
    pictureBox.Image = img;
    pbImage = img;
    ...
    pictureBox.Paint += pictureBox_Paint;
}

void pictureBox_Paint(object sender, PaintEventArgs e)
{
    if (pbImage == null) { return; }
    var drawRect = new Rectangle(startX, startY, pictureBox.Width, pictureBox.Height);
    e.Graphics.DrawImageUnscaledAndClipped(this.pbImage, drawRect);
}

private void toolStripSplitButton1_ButtonClick(object sender, EventArgs e)
{
    ///... resize to what you need 
    pictureBox.Width = (int) (pbImage.Width*0.2);
    pictureBox.Height = (int) (pbImage.Height * 0.2);
    pictureBox.Invalidate();
}