This problem occurs when a watermark image is generated! (Graphics objects cannot be created from images with indexed pixel formats .)

The main reason is that the original type of the uploaded image is GIF, so you must first map the original image, and then save the bitmap.

 

/// <Summary>
/// Add a watermark to the image
/// </Summary>
/// <Param name = "strpath"> original file </param>
/// <Param name = "strpathsyp"> watermark file </param>
/// <Param name = "strpathsypf"> watermark result file </param>

Public static void addwaterpic (string strpath, string strpathsyp, string strpathsypf)
{
System. Drawing. Image image = system. Drawing. image. fromfile (strpath );
Bitmap Bm = new Bitmap (image );

System. Drawing. Image copyimage = system. Drawing. image. fromfile (strpathsyp );

System. Drawing. Graphics G = system. Drawing. Graphics. fromimage (BM );

// If You Want to center the watermark, you only need to change the values of BM. Width-copyimage. Width and BM. Height-copyimage. Height.

// You can use convert. toint32 (image. Width * 0.3), convert. toint32 (image. Height * 0.3)

G. drawimage (copyimage, new system. drawing. rectangle (BM. width-copyimage. width, BM. height-copyimage. height, copyimage. width, copyimage. height), 0, 0, copyimage. width, copyimage. height, system. drawing. graphicsunit. pixel );
G. Dispose ();
Copyimage. Dispose ();
BM. Save (strpathsypf );
BM. Dispose ();
}