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我的网页有文件上传选项..它必须检查两个条件。1）所选项目是否为图像..如果图像表示则仅允许用户执行，否则不会。2）检查选定的图像尺寸（它只允许有限的尺寸）

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2 回答 2

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要判断文件是否为图像，只需查看扩展名 (System.File.Path.GetExtension)。您可以轻松调整图像大小并确保它不超过特定大小：

public static Bitmap CreateThumbnail(Bitmap loBMP, int lnWidth, int lnHeight)
{
    System.Drawing.Bitmap bmpOut = null;
    try
    {
        ImageFormat loFormat = loBMP.RawFormat;

        decimal lnRatio;
        int lnNewWidth = 0;
        int lnNewHeight = 0;

        if (loBMP.Width < lnWidth && loBMP.Height < lnHeight)
            return loBMP;

        if (loBMP.Width > loBMP.Height)
        {
            lnRatio = (decimal)lnWidth / loBMP.Width;
            lnNewWidth = lnWidth;
            decimal lnTemp = loBMP.Height * lnRatio;
            lnNewHeight = (int)lnTemp;
        }

        else
        {
            lnRatio = (decimal)lnHeight / loBMP.Height;
            lnNewHeight = lnHeight;
            decimal lnTemp = loBMP.Width * lnRatio;
            lnNewWidth = (int)lnTemp;
        }

        bmpOut = new Bitmap(lnNewWidth, lnNewHeight);
        Graphics g = Graphics.FromImage(bmpOut);
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        g.FillRectangle(Brushes.White, 0, 0, lnNewWidth, lnNewHeight);
        g.DrawImage(loBMP, 0, 0, lnNewWidth, lnNewHeight);
    }
    catch
    {
        return null;
    }

    return bmpOut;
}
于 2012-06-25T05:17:05.733 回答
0

  1. 您可以使用 RegularExpressionValidator 使其变得简单

     <asp:FileUpload ID="UploadFile" runat="server" />
 <asp:RegularExpressionValidator id="UpLoadValidator" runat="server" ErrorMessage="Upload Images only." ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))(.jpg|.png|.bmp|.jpeg|.gif)$" ControlToValidate="FileUpload1"> </asp:RegularExpressionValidator>

  2. 在 web.config 中设置图像最大尺寸

    <system.webServer>
<security>
  <requestFiltering>
    <requestLimits maxAllowedContentLength="524288"/>
  </requestFiltering>
</security>
</system.webServer>
于 2012-06-25T05:40:22.157 回答