如何调整图像大小以从数据库中显示

本文关键字：数据库 显示 图像 何调整 调整 | 更新日期: 2023-09-27 18:20:35

我正在做一个小项目，必须将数据库中的所有图像显示到Listview。我将图像id、宽度和高度作为querystring参数传递。

<asp:Image ID="Image1" runat="server" ImageUrl='<%#"~/Handler/ImageHandler.ashx?ImgHeight=150&ImgWidth=200&ImgID="+Eval("Image_ID")%>' Height="150px" Width="200px"/>
public void ProcessRequest (HttpContext context) 
    {
    string imgwidth = context.Request.QueryString["ImgWidth"];
    string imgheight = context.Request.QueryString["ImgHeight"];
    string imageid = context.Request.QueryString["ImgID"];
    if (imgwidth != string.Empty && imgheight != string.Empty && (imgwidth != null && imgheight != null))
    {
        if (!System.Web.UI.WebControls.Unit.Parse(imgwidth).IsEmpty && !System.Web.UI.WebControls.Unit.Parse(imgheight).IsEmpty)
        {
            //create unit object for height and width. This is to convert parameter passed in differen unit like pixel, inch into generic unit.
            System.Web.UI.WebControls.Unit widthUnit=System.Web.UI.WebControls.Unit.Parse(imgwidth);
            System.Web.UI.WebControls.Unit heightUnit = System.Web.UI.WebControls.Unit.Parse(imgheight);
            //AFTER THIS ???
        }
    }
}

当我直接从数据库中显示图像时，有些图像会拉伸，看起来不太好，这是因为图像大小太大。所以我需要在图片库中为拇指蜗牛显示这些图片。

如何调整图像大小以从数据库中显示

您可以使用GetThumbnailImage方法

参考代码

public Void GenerateImage(int iWidth,int iHeight,byte[] ImageBytes)
{
System.Drawing.Image image = byteArrayToImage(ImageBytes)
 // create the actual thumbnail image
        System.Drawing.Image thumbnailImage = image.GetThumbnailImage(iWidth, iHeight, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);
        // make a memory stream to work with the image bytes
        MemoryStream imageStream = new MemoryStream();
        // put the image into the memory stream
        thumbnailImage.Save(imageStream, System.Drawing.Imaging.Imageformat.Jpeg);
        // make byte array the same size as the image
        byte[] imageContent = new Byte[imageStream.Length];
        // rewind the memory stream
        imageStream.Position = 0;
        // load the byte array with the image
        imageStream.Read(imageContent, 0, (int)imageStream.Length);
        // return byte array to caller with image type
        Response.ContentType = "image/jpeg";
        Response.BinaryWrite(imageContent);
    }
    public bool ThumbnailCallback()
    {
        return true;
    }
public Image byteArrayToImage(byte[] byteArrayIn)
{
     MemoryStream ms = new MemoryStream(byteArrayIn);
     Image returnImage = Image.FromStream(ms);
     return returnImage;
}

您可以使用此代码为图像提供新的大小，同时保留纵横比：

public static Image ResizeCanvas(Image original, Size newSize, Color background)
    {
        int xStart = (newSize.Width / 2) - (original.Width / 2);
        int yStart = (newSize.Height / 2) - (original.Height / 2);
        // Create blank canvas
        Bitmap resizedImg = new Bitmap(newSize.Width, newSize.Height);
        Graphics gfx = Graphics.FromImage(resizedImg);
        // Fill canvas
        gfx.FillRectangle(new SolidBrush(background), new Rectangle(new Point(0, 0), newSize));
        gfx.DrawImage(original, xStart, yStart, original.Width, original.Height);
        return resizedImg;
    }
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