Home > Developer > .Net Core

Asp.net dynamic output transparent GIF Image

Source: Internet
Author: User
Developer on Alibaba Coud: Build your first app with APIs, SDKs, and tutorials on the Alibaba Cloud. Read more ＞

I checked a few Chinese documents in China and found a usable Method on an English blog.
The solution code is:

Code
Copy codeThe Code is as follows:
// Save as gif. ashx
<% @ WebHandler Language = "C #" Class = "Gif" %>
Using System. IO;
Using System. Web;
Using System. Drawing;
Public class Gif: IHttpHandler {
/// <Summary>
/// Returns a transparent background GIF image from the specified Bitmap.
/// </Summary>
/// <Param name = "bitmap"> The Bitmap to make transparent. </param>
/// <Param name = "color"> The Color to make transparent. </param>
/// <Returns> New Bitmap containing a transparent background gif. </returns>
Public Bitmap MakeTransparentGif (Bitmap bitmap, Color color ){
Byte R = color. R;
Byte G = color. G;
Byte B = color. B;
MemoryStream fin = new MemoryStream ();
Bitmap. Save (fin, System. Drawing. Imaging. ImageFormat. Gif );
MemoryStream fout = new MemoryStream (int) fin. Length );
Int count = 0;
Byte [] buf = new byte [1, 256];
Byte transparentIdx = 0;
Fin. Seek (0, SeekOrigin. Begin );
// Header
Count = fin. Read (buf, 0, 13 );
If (buf [0]! = 71) | (buf [1]! = 73) | (buf [2]! = 70) return null; // GIF
Fout. Write (buf, 0, 13 );
Int I = 0;
If (buf [10] & 0x80)> 0 ){
I = 1 <(buf [10] & 7) + 1) = 256? 256: 0;
}
For (; I! = 0; I --){
Fin. Read (buf, 0, 3 );
If (buf [0] = R) & (buf [1] = G) & (buf [2] = B )){
TransparentIdx = (byte) (256-I );
}
Fout. Write (buf, 0, 3 );
}
Bool gcePresent = false;
While (true ){
Fin. Read (buf, 0, 1 );
Fout. Write (buf, 0, 1 );
If (buf [0]! = 0x21) break;
Fin. Read (buf, 0, 1 );
Fout. Write (buf, 0, 1 );
GcePresent = (buf [0] = 0xf9 );
While (true ){
Fin. Read (buf, 0, 1 );
Fout. Write (buf, 0, 1 );
If (buf [0] = 0) break;
Count = buf [0];
If (fin. Read (buf, 0, count )! = Count) return null;
If (gcePresent ){
If (count = 4 ){
Buf [0] | = 0x01;
Buf [3] = transparentIdx;
}
}
Fout. Write (buf, 0, count );
}
}
While (count> 0 ){
Count = fin. Read (buf, 0, 1 );
Fout. Write (buf, 0, 1 );
}
Fin. Close ();
Fout. Flush ();
Return new Bitmap (fout );
}
Public void ProcessRequest (HttpContext context ){
Bitmap transGif = null;
Using (Bitmap bmp = new Bitmap (300, 50 )){
Using (Graphics g = Graphics. FromImage (bmp )){
G. Clear (Color. Gray );
G. DrawString ("transparent gif image ",
New Font ("verdana bold", 14f), Brushes. LemonChiffon, 0f, 0f );
Bmp. MakeTransparent (Color. Gray );
TransGif = MakeTransparentGif (bmp, Color. Black );
}
}
If (transGif! = Null ){
Context. Response. Clear ();
Context. Response. ContentType = "image/GIF ";
TransGif. Save (context. Response. OutputStream,
System. Drawing. Imaging. ImageFormat. Gif );
}
}
Public bool IsReusable {get {return false ;}}
}

The test html file is as follows:

Copy codeThe Code is as follows:
<! DOCTYPE html PUBLIC "-// W3C // dtd xhtml 1.0 Transitional // EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<Html xmlns = "http://www.w3.org/1999/xhtml">
<Head>
<Title> </title>
</Head>
<Body style = "background: #999">
text below
</Body>
</Html>

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
create transparent gif pixel transparent gif transparent gif generator convert to transparent gif download transparent gif gif transparent background transparent pixel gif
Related Article
asp.net Core Data protection (the data Protection cluster sce...
asp.net core-authorize characteristics
Micro-service Monitoring zipkin+asp.net core
Combine ASP NET Core and SQL Server with Docker Compose
ASP. net mvc creates 404 jump instances (not 302 and 200), mv...
Comparison between Orchard and ABP architectures (aspnetboile...

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

What's Trending
Top 10 Tags
datastax versions naming convention zookeeper client class definition md5 microsoft sql server 2005 data structures exception handling error handling
Top 10 Keywords
microsoft download center down wordpress address url site address url wordpress address url windows installer 4 0 download 302 not found web address url definition site address url wordpress db2 integer mac os installation step by step pdf abbreviation for return

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

Get Started for Free

  • Sales Support

    1 on 1 presale consultation

    Chat Contact Sales

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

    Open a Ticket

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.

    Learn More