取得網路上的圖片並儲存－冠霖的部落格

轉:   from : http://www.dotblogs.com.tw/shadow/archive/2011/11/23/59286.aspx
與前一篇QRCODE   有關
:P
產生QRCODE後取圖片

/*要先using以下兩個命名空間*/

using System.IO;

using System.Net;

 //Page_Load事件

 protected void Page_Load(object sender, EventArgs e)

    {

        if (!IsPostBack)

        {

            string srcImageUrl = "https://chart.googleapis.com/chart?chs=120x120&cht=qr&chl=http://www.google.com.tw&choe=UTF-8&chld=M|2";

            //儲存圖片在Server上

            this.saveThumbPic(srcImageUrl, 100, Server.MapPath("~/test.jpg"));

            //Response給用戶端下載

            FileStream fs = new FileStream(Server.MapPath("~/test.jpg"), FileMode.Open);

            byte[] file = new byte[fs.Length];

            fs.Read(file, 0, file.Length);

            fs.Close();

            Response.Clear();

            Response.AddHeader("content-disposition", "attachment; filename=test.jpg");//強制下載

            Response.ContentType = "image/jpg";

            Response.BinaryWrite(file);

        }

    }

    #region 取得網路上的圖片

    /// <summary>

    /// 取得網路上的圖片

    /// </summary>

    /// <param name="strUrl">圖片的Url路徑</param>

    /// <returns>回傳 System.Drawing.Image物件</returns>

    public System.Drawing.Image getImageFromURL(string strUrl)

    {

        System.Drawing.Image MyImage = null;

        try

        {

            //建立一個 Web Request

            WebRequest MyWebRequest = WebRequest.Create(strUrl);

            //由 Web Request 取得 Web Response

            WebResponse MyWebResponse = MyWebRequest.GetResponse();

            //由 Web Response 取得 Stream

            Stream MyStream = MyWebResponse.GetResponseStream();

            //由 Stream 取得 Image

            MyImage = System.Drawing.Image.FromStream(MyStream);

            //該關的關一關, 該放的放一放

            MyStream.Close();

            MyStream.Dispose();

            MyWebResponse.Close();

            MyWebResponse = null;

            MyWebRequest = null;

        }

        catch (Exception ex)

        {

            throw new Exception("getImageFromURL(string strUrl)發生例外，可能抓不到網路上的圖片" + strUrl);

        }

        //回傳 Image

        return MyImage;

    }

    #endregion 

    #region [ASP.net程式使用]圖片等比例縮圖後的寬和高像素

    /// <summary>

    /// [ASP.net程式使用]取得圖片等比例縮圖後的寬和高像素

    /// </summary>

    /// <param name="image">System.Drawing.Image 的物件</param>

    /// <param name="maxPx">寬或高超過多少像素就要縮圖</param>

    /// <returns>回傳int陣列，索引0為縮圖後的寬度、索引1為縮圖後的高度</returns>

    public int[] getThumbPic_WidthAndHeight(System.Drawing.Image image, int maxPx)

    {

        int fixWidth = 0;

        int fixHeight = 0;

        if (image.Width > maxPx || image.Height > maxPx)

        //如果圖片的寬大於最大值或高大於最大值就往下執行  

        {

            if (image.Width >= image.Height)

            //圖片的寬大於圖片的高  

            {

                fixHeight = Convert.ToInt32((Convert.ToDouble(maxPx) / Convert.ToDouble(image.Width)) * Convert.ToDouble(image.Height));

                //設定修改後的圖高  

                fixWidth = maxPx;

            }

            else

            {

                fixWidth = Convert.ToInt32((Convert.ToDouble(maxPx) / Convert.ToDouble(image.Height)) * Convert.ToDouble(image.Width));

                //設定修改後的圖寬  

                fixHeight = maxPx;

            }

        }

        else

        {//圖片沒有超過設定值，不執行縮圖  

            fixHeight = image.Height;

            fixWidth = image.Width;

        }

        int[] fixWidthAndfixHeight = { fixWidth, fixHeight };

        return fixWidthAndfixHeight;

    }

    #endregion

    #region 產生縮圖並儲存

    /// <summary>

    /// 產生縮圖並儲存

    /// </summary>

    /// <param name="srcImageUrl">來源圖片的Url</param>

    /// <param name="maxPix">超過多少像素就要等比例縮圖</param>

    /// <param name="saveThumbFilePath">縮圖的儲存檔案路徑</param>

    public void saveThumbPic(string srcImageUrl, int maxPix, string saveThumbFilePath)

    {

        //為了callBack而callBack的寫法

        System.Drawing.Image.GetThumbnailImageAbort callBack =

             new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);

        //取得原始圖片

        System.Drawing.Image image = this.getImageFromURL(srcImageUrl);

        // 計算維持比例的縮圖大小

        int[] thumbnailScale = this.getThumbPic_WidthAndHeight(image, maxPix);

        // 產生縮圖

        System.Drawing.Image smallImage =

        image.GetThumbnailImage(thumbnailScale[0], thumbnailScale[1], callBack, IntPtr.Zero);

        // 將縮圖存檔

        smallImage.Save(saveThumbFilePath);

        // 釋放

        image.Dispose();

    }

    private bool ThumbnailCallback()

    {

        return false;

    }

    #endregion