在 ASP.NET 網頁上加入浮水印

通常在Confidential的頁面上會顯示浮水印，這樣當User在拍下畫面時，至少知道是誰在何時外流的...

首先撰寫產出圖型的 WaterMark.ashx，欲顯示的文字內容可視情況調整...

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<%@ WebHandler Language="C#" Class="WaterMark" %>

using System;
using System.Web;

public class WaterMark : IHttpHandler {

    public void ProcessRequest (HttpContext context) {
        byte[] myPic = null;
        string id = context.Request["id"];
        myPic = createImg(id, 22, 20, 300, 180);
        context.Response.ContentType = "image/png";
        context.Response.OutputStream.Write(myPic, 0, myPic.Length);
    }

    public bool IsReusable {
        get {
            return true;
        }
    }

    private byte[] createImg(string strWaterMark, float f1, float f2, int w, int h)
    {
        Bitmap newBitmap = null;
        Graphics g = null;
        MemoryStream ms = new MemoryStream();
        try
        {
            Font fontCounter = new Font("Lucida Sans Unicode", f1);
            Font fontCounter2 = new Font("Lucida Sans Unicode", f2);
            // calculate size of the string.
            newBitmap = new Bitmap(1, 1, PixelFormat.Format32bppArgb);
            g = Graphics.FromImage(newBitmap);
            SizeF stringSize = g.MeasureString(strWaterMark, fontCounter);
            int nWidth = (int)stringSize.Width;
            int nHeight = (int)stringSize.Height;
            g.Dispose();
            newBitmap.Dispose();
            newBitmap = new Bitmap(w, h, PixelFormat.Format32bppArgb);
            g = Graphics.FromImage(newBitmap);
            g.FillRectangle(new SolidBrush(Color.White), new Rectangle(0, 0, w, h));
            g.RotateTransform(23.0F);
            g.DrawString("Rexchip Confidential", fontCounter2, new SolidBrush(Color.Black), 40, 0 - 20);
            g.DrawString("Printed by " + strWaterMark, fontCounter, new SolidBrush(Color.Black), 40, nHeight * 0.5f - 20);
            g.DrawString(DateTime.Now.ToString("yyyy-MM-dd HH:mm"), fontCounter2, new SolidBrush(Color.Black), 40, nHeight * 1.2f - 20);
            newBitmap.Save(ms, ImageFormat.Png);
        }
        catch (Exception e) {}
        finally
        {
            if (null != g) g.Dispose();
            if (null != newBitmap) newBitmap.Dispose();
        }
        return ms.ToArray();
    }
}

然後到要顯示浮水印的頁面增加一個 div 及 img html控制項，div 用來塞浮水印 image，div 視情況調整top及left位置...

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class="bgMark" 可設定浮水印的濃度，CSS如下:

.bgMark
{
    filter:alpha(opacity=8);
    -moz-opacity:0.08;
    opacity: 0.08;
}

再來就是要產生浮水印，並指定到 div了，後端程式如下:

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    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            //浮水印背景設定
            string script = "document.getElementById('bgMark').style.background = \"url(\" + document.getElementById('"
                + imgWaterMark.ClientID + "').src + \")  0 20  repeat \";";

            if (ScriptManager.GetCurrent(this.Page) == null)
                Page.ClientScript.RegisterStartupScript(this.Page.GetType(), "block", script, true);
            else
                ScriptManager.RegisterStartupScript(this.Page, this.Page.GetType(), "block", script, true);

            //浮水印圖
            string ID = getUserID();
            imgWaterMark.Src = ResolveUrl("~") + string.Format("WaterMark.ashx?id={0}", ID);
        }
    }

posted @ 2013-06-11 09:52 Jimmych 阅读(1499) 评论(0) 收藏举报

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