Asp. NET knowledge summary (generic handler for dynamic processing of pictures (CAPTCHA, watermark, thumbnail))

-"Use GDI + to complete the processing of pictures, need to introduce assembly System.Drawing

-" the basic processing model of GDI +

"1" Create canvas Bitmap

"2" Create drawing Tool object Graphics

"3" Call draw***,fill*** Series method to complete the drawing

"4" saved, can be saved to the physical file, can also be saved to the output stream

For use in ashx , you need to specify contenttype= "Image/jpeg";

Use the Save () method output from the canvas object to output to a physical file or output to a stream

Use:

-" example 1: Generate watermark Map "

Idea: Draw a text or small picture on the original image

Example:ASPNET Project Review / /t2_gditest/addwaterof the next day

-" example 2: Generate a verification code

IDEA: Create a canvas, randomly generate characters and draw

Additional function: "Can't see Clearly, change one"

Example:ASPNET Project Review / /t2_gditest/validatecodeof the next day

-" example 3: Thumbnail image "

Idea: Draw the original image to a new diagram and complete the physical save in a scaled-down scale

Example:ASPNET Project Review / /t2_gditest/scaletestof the next day

Asp. NET knowledge summary (generic handler for dynamic processing of pictures (CAPTCHA, watermark, thumbnail))