在 listview 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在列表视图中调整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this answer 中有专门用于调整图像大小和分辨率的代码：

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);
    }

}