Question

我一直在努力将图像的缩略图添加到网格视图中，以便图像可以显示为原始图像的较小版本。

我仍然在学习C＃编码，希望能得到一些帮助。我设法上传图片，甚至显示图片，但是将其设置为thumnail大小是有问题的。

我将插入一些代码作为众多尝试之一（所有这些都会返回错误）

亲切的问候

if (upImage.HasFile)
    {
        try
        {
            string filename = Path.GetFileName(upImage.FileName);
            //****************************************************

            System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(Server.MapPath("~/") + filename);

            System.Drawing.Image thumbNail = sourceImage.GetThumbnailImage(70, 70, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);

            thumbNail.Save(Path.ChangeExtension(filename, "thumb"));

            upImage.SaveAs(Server.MapPath("~/") + filename);


            //upImage.SaveAs(Server.MapPath("~/") + filename);
            lblUpload.Text = "Upload status: File uploaded!";
        }
        catch (Exception ex)
        {
            lblUpload.Text = "Upload status: The file could not be uploaded. The following error occured: " + ex.Message;
        }
    }

public bool ThumbnailCallback()
{
    return true;
}

Answer 1

public void Thumb(string file) 
{
    System.Drawing.Image image = System.Drawing.Image.FromFile(Server.MapPath(file));
    System.Drawing.Image thumbnailImage = image.GetThumbnailImage(70, 70, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);
    System.IO.MemoryStream imageStream = new System.IO.MemoryStream();
    thumbnailImage.Save(imageStream, System.Drawing.Imaging.ImageFormat.Jpeg);
    byte[] imageContent = new Byte[imageStream.Length];
    imageStream.Position = 0;
    imageStream.Read(imageContent, 0, (int)imageStream.Length);
    Response.ContentType = "image/jpeg";
    Response.BinaryWrite(imageContent);
}

使用此功能，您将获得图像的缩略图，您可以在任何地方使用它。希望这有助于：）

Answer 2

这是简短的回答：

private static MemoryStream GetImageResized(MemoryStream data, int previewWidth, int previewHeight)
{
    const int pixelPadding = 6;
    const int bottomSize = 0;

    using (var src = new Bitmap(data))
    {
        // default to width-based resizing...
        int width = previewWidth;
        var height = (int)(previewWidth / (src.Width / (double)src.Height));

        if (src.Width <= previewWidth && src.Height <= previewHeight)
        {
            // no resizing necessary...
            width = src.Width;
            height = src.Height;
        }
        else if (height > previewHeight)
        {
            // aspect is based on the height, not the width...
            width = previewHeight / ((src.Height / src.Width) == 0 ? 1 : (src.Height / src.Width));
            height = previewHeight;
        }

        using (
          var dst = new Bitmap(width + pixelPadding, height + bottomSize + pixelPadding, PixelFormat.Format24bppRgb))
        {
            var rSrcImg = new Rectangle(0,0, src.Width, src.Height);
            var rDstImg = new Rectangle(pixelPadding / 2, pixelPadding/2, dst.Width - pixelPadding, dst.Height - pixelPadding - bottomSize);
            using (Graphics g = Graphics.FromImage(dst))
            {
                g.Clear(Color.FromArgb(64, 64, 64));
                g.FillRectangle(Brushes.White, rDstImg);

                g.CompositingMode = CompositingMode.SourceOver;
                g.CompositingQuality = CompositingQuality.GammaCorrected;
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.InterpolationMode = InterpolationMode.HighQualityBicubic;

                g.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
                g.DrawImage(src, rDstImg, rSrcImg, GraphicsUnit.Pixel);
            }

            var ms = new MemoryStream();

            // save the bitmap to the stream...
            dst.Save(ms, ImageFormat.Png);
            ms.Position = 0;

            return ms;
        }
    }
}

您可以调用此方法来调整图像大小。例如：

private void GetThumbnailImage(HttpContext context, string fileName, int maxWidth, int maxHeight)
{
var data = new MemoryStream();
using (var input = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read))
{
    var buffer = new byte[input.Length];
    input.Read(buffer, 0, buffer.Length);
    data.Write(buffer, 0, buffer.Length);
    input.Close();
}

// reset position...
data.Position = 0;

MemoryStream ms = GetImageResized(
  data, maxWidth, maxHeight);

context.Response.ContentType = "image/png";

// output stream...
context.Response.OutputStream.Write(ms.ToArray(), 0, (int)ms.Length);
// Possible Caching
//context.Response.Cache.SetCacheability(HttpCacheability.Public);
//context.Response.Cache.SetExpires(DateTime.UtcNow.AddHours(2));
//context.Response.Cache.SetETag(...);

data.Dispose();
ms.Dispose();
}

我写了一篇关于它的文章。代码示例已附在文章中。这篇文章是波斯文，但你可以使用谷歌翻译。 http://www.devzone.ir/post/1389/09/16/Dynamic-Thumbnails-in-ASP.aspx

将缩略图添加到gridview

2 个答案: