在列表视图控件上动态创建固定大小的缩略图

Question

如何动态创建固定大小的缩略图并调整列表视图中的图像大小以最适合缩略图的大小。

private void Treeview1_AfterSelect(System.Object sender, System.Windows.Forms.TreeViewEventArgs e)
{
    if (folder != null && System.IO.Directory.Exists(folder))
                {
                    try
                    {

                        DirectoryInfo dir = new DirectoryInfo(@folder);
                        foreach (FileInfo file in dir.GetFiles())
                        {
                            try
                            {
                                imageList.ImageSize = new Size(136, 136);
                                imageList.ColorDepth = ColorDepth.Depth32Bit;
                                Image img = new Bitmap(Image.FromFile(file.FullName));                                    
                                Graphics g = Graphics.FromImage(img);

                                g.DrawRectangle(Pens.Red, 0, 0, img.Width - 21, img.Height - 21);
                                //g.DrawRectangle(Pens.Red, 0, 0, img.Width, img.Height);                                                                                                                                                
                                imageList.Images.Add(img);
                            }
                            catch
                            {
                                Console.WriteLine("This is not an image file");
                            }     
                        }


                        for (int j = 0; j < imageList.Images.Count; j++)
                        {
                            this.ListView1.Items.Add("Item" + j);
                            this.ListView1.Items[j].ImageIndex = j;
                        }

                        this.ListView1.View = View.LargeIcon;
                        this.ListView1.LargeImageList = imageList;
                        //this.ListView1.DrawItem += new DrawListViewItemEventHandler(ListView1_DrawItem);                                                       

                        //import(folder);
                    }
                    catch (Exception ex)
                    {
                    }
}

Answer 1

我在这个答案中有代码专门用于调整图像大小和分辨率：

public void GenerateThumbNail(HttpPostedFile fil, string sPhysicalPath, 
                              string sOrgFileName,string sThumbNailFileName,
                              ImageFormat oFormat, int rez)
{

    try
    {

        System.Drawing.Image oImg = System.Drawing.Image.FromStream(fil.InputStream);

        decimal pixtosubstract = 0;
        decimal percentage;

        //default
        Size ThumbNailSizeToUse = new Size();
        if (ThumbNailSize.Width < oImg.Size.Width || ThumbNailSize.Height < oImg.Size.Height)
        {
            if (oImg.Size.Width > oImg.Size.Height)
            {
                percentage = (((decimal)oImg.Size.Width - (decimal)ThumbNailSize.Width) / (decimal)oImg.Size.Width);
                pixtosubstract = percentage * oImg.Size.Height;
                ThumbNailSizeToUse.Width = ThumbNailSize.Width;
                ThumbNailSizeToUse.Height = oImg.Size.Height - (int)pixtosubstract;
            }
            else
            {
                percentage = (((decimal)oImg.Size.Height - (decimal)ThumbNailSize.Height) / (decimal)oImg.Size.Height);
                pixtosubstract = percentage * (decimal)oImg.Size.Width;
                ThumbNailSizeToUse.Height = ThumbNailSize.Height;
                ThumbNailSizeToUse.Width = oImg.Size.Width - (int)pixtosubstract;
            }

        }
        else
        {
            ThumbNailSizeToUse.Width = oImg.Size.Width;
            ThumbNailSizeToUse.Height = oImg.Size.Height;
        }

        Bitmap bmp = new Bitmap(ThumbNailSizeToUse.Width, ThumbNailSizeToUse.Height);
        bmp.SetResolution(rez, rez);
        System.Drawing.Image oThumbNail = bmp;

        bmp = null;

        Graphics oGraphic = Graphics.FromImage(oThumbNail);

        oGraphic.CompositingQuality = CompositingQuality.HighQuality;

        oGraphic.SmoothingMode = SmoothingMode.HighQuality;

        oGraphic.InterpolationMode = InterpolationMode.HighQualityBicubic;

        Rectangle oRectangle = new Rectangle(0, 0, ThumbNailSizeToUse.Width, ThumbNailSizeToUse.Height);

        oGraphic.DrawImage(oImg, oRectangle);

        oThumbNail.Save(sPhysicalPath  + sThumbNailFileName, oFormat);

        oImg.Dispose();

    }
    catch (Exception ex)
    {
        Response.Write(ex.Message);
    }

}