How to Implement watermarks in asp.net

Watermarks are used to prevent image theft.

Two ways to achieve the watermark Effect

1) You can add a watermark when uploading a file.

A) Benefits: Compared with the two methods, each time a user reads the image, the server sends it directly to the customer.

B) Disadvantage: the original image is damaged.

2) use a general global processing program to add a watermark when the user requests this image.

A) benefits: the original image is not damaged.

B) Disadvantages: users need to add watermarks to the requested images each time they request them, wasting server resources.

The second method of code implementation:
Copy codeThe Code is as follows:
Using System;
Using System. Collections. Generic;
Using System. Linq;
Using System. Web;
Using System. Drawing;
Using System. IO;

Namespace BookShop. Web
{
Public class WaterMark: IHttpHandler
{

Private const string WATERMARK_URL = "~ /Images/watermark.jpg "; // watermark image
Private const string DEFAULTIMAGE_URL = "~ /Images/default.jpg "; <span style =" white-space: pre "> </span> // default image
# Region IHttpHandler Member

Public bool IsReusable
{
Get {return false ;}
}

Public void ProcessRequest (HttpContext context)
{

// Context. Request. PhysicalPath // obtain the physical path of the file requested by the user

System. Drawing. Image Cover;
// Determine whether a file exists in the request's physical path
If (File. Exists (context. Request. PhysicalPath ))
{
// Load the file
Cover = Image. FromFile (context. Request. PhysicalPath );
// Load the watermark image
Image watermark = Image. FromFile (context. Request. MapPath (WATERMARK_URL ));
// Use the cover of the book to obtain the Drawing Object
Graphics g = Graphics. FromImage (Cover );
// Draw a watermark on the image
G. DrawImage (watermark, new Rectangle (Cover. Width-watermark. Width, Cover. Height-watermark. Height,

Copy codeThe Code is as follows:
Watermark. Width, watermark. Height), 0, 0, watermark. Width, watermark. Height, GraphicsUnit. Pixel );
// Release the canvas
G. Dispose ();
// Release the watermark image
Watermark. Dispose ();
}
Else
{
// Load the default image
Cover = Image. FromFile (context. Request. MapPath (DEFAULTIMAGE_URL ));
}
// Set the output format
Context. Response. ContentType = "image/jpeg ";
// Save the image to the output stream
Cover. Save (context. Response. OutputStream, System. Drawing. Imaging. ImageFormat. Jpeg );
Cover. Dispose ();
Context. Response. End ();
}

# Endregion
}
}