c# - Windows窗体中的Panel和ScrollBar

我正在使用面板在Windows窗体中显示图像
我在Panel_Paint事件中的面板中绘制图像，如下所示：

Graphics g = panel1.CreateGraphics();
Image im = new Bitmap(@"../../Data/#3_Page2.PNG");
g.DrawImage(im,new Point(10,10));

现在，按照我的预期绘制图像，图像底部的某些部分由于高度大于表单高度而未显示。
我现在添加了VScrollBar。我如何使该面板在VScrollBar的帮助下查看其余图像。

最佳答案

此解决方案有效，但是，如果您的图像足够大，则滚动时会出现一点闪烁（但是可以接受）。首先，您必须在面板右侧添加一个VScrollBar，在面板底部下方添加一个HScrollBar。此演示要求您有一个名为VScrollBar的vScrollBar1和一个HScrollBar的hScrollBar1，一个名为Button的buttonOpenImage允许用户打开某些图像，一个名为Panel的panel1用作主图像。绘制图像的区域：

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        //To prevent/eliminate flicker, do this
        typeof(Panel).GetProperty("DoubleBuffered",
                                  System.Reflection.BindingFlags.Instance |
               System.Reflection.BindingFlags.NonPublic).SetValue(panel1, true, null);
        //------------------------
        UpdateScrollbarsState();
    }
    int imgWidth, imgHeight;
    Image image;
    Point leftTop = Point.Empty;
    int lastV, lastH;
    private void OpenImage(){
        OpenFileDialog openFile = new OpenFileDialog();
        openFile.FileOk += (s, e) => {
            try {
                image = Image.FromFile(openFile.FileName);
                //calculate the physical size of the image based on the resolution and its logical size.
                //We have to do this because the DrawImage is based on the physical size (not logical).
                imgWidth = (int)(image.Width * 96f / image.HorizontalResolution + 0.5);
                imgHeight = (int)(image.Height * 96f / image.VerticalResolution + 0.5);
                lastV = lastH = 0;
                UpdateScrollbarsState();
                vScrollBar1.Value = 0;
                hScrollBar1.Value = 0;
                panel1.Invalidate();
            }
            catch {
                image = null;
                MessageBox.Show("Image file is invalid or corrupted!");
            }
        };
        openFile.ShowDialog();
    }
    private void UpdateScrollbarsState() {
        //We have to update all the info about Minimum and Maximum
        vScrollBar1.Minimum = 0;
        hScrollBar1.Minimum = 0;
        vScrollBar1.Maximum = Math.Max(imgHeight-panel1.Height,0);
        hScrollBar1.Maximum = Math.Max(imgWidth-panel1.Width,0);
        vScrollBar1.Visible = vScrollBar1.Maximum > 0;
        hScrollBar1.Visible = hScrollBar1.Maximum > 0;
        if (vScrollBar1.Maximum == 0) {
            leftTop.Y = 0;
            lastV = 0;
        }
        if (hScrollBar1.Maximum == 0) {
            leftTop.X = 0;
            lastH = 0;
        }
    }
    private void panel1_Paint(object sender, PaintEventArgs e) {
        if (image == null) return;
        e.Graphics.DrawImage(image, leftTop);
    }
    //The ValueChanged event handler of your vScrollBar1
    private void vScrollBar1_ValueChanged(object sender, EventArgs e) {
        if (!vScrollBar1.Visible) return;
        leftTop.Offset(0, -vScrollBar1.Value + lastV);
        lastV = vScrollBar1.Value;
        panel1.Invalidate();
    }
    //The ValueChanged event handler of your hScrollBar1
    private void hScrollBar1_ValueChanged(object sender, EventArgs e) {
        if (!hScrollBar1.Visible) return;
        leftTop.Offset(lastH - hScrollBar1.Value, 0);
        lastH = hScrollBar1.Value;
        panel1.Invalidate();
    }
    //handler for SizeChanged event of the panel. However if resizing
    //the form causes the panel's size changing, you should attach this
    //handler for form.
    private void panel1_SizeChanged(object sender, EventArgs e) {
        UpdateScrollbarsState();
    }
    //handler for the Click event of a button (click to open an image)
    private void buttonOpenImage_Click(object sender, EventArgs e) {
        OpenImage();
    }
}

关于c# - Windows窗体中的Panel和ScrollBar，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/17970141/