I am reading Chapter 8 "Drawing Pixels, Bitmaps, Fonts and Images" of the red book OpenGL Programming Guide (5th edition).

I'd like to do the following:
  • 1. Read a typical internet image (gif, jpg, png, etc)

  • 2. Display it on WebGL

  • 3. Do some manipulations on the image

  • 4. Read back the new (manipulated) image

  • 5. Save the new image into gif, jpg or png

Where can I find a sample code and/or document to do (some of the) above?

Thanks in advance for your help.