A canvas widget doesn't support to access per pixel.
Although you can do that if each pixel is represented by a line item,
that will be incredibly slow.
If you want to do that, I think, you'll have to use a PhotoImage object.
On a PhotoImage, you can access and change the color of any pixel.
Please use TkPhotoImage#get and TkPhotoImage#put.
And please read "photo" manual of Tcl/Tk.
Stadard Tcl/Tk libraries supports only GIF and PPM/PGM.
If you want to treat other image formats,
please use "Img" extesion of Tcl/Tk.
Hidetoshi NAGAI (na...@ai.kyutech.ac.jp)