[Image-SIG] Creating a Transparent Image and Placing it Over Another Image (txt)

Wayne Watson sierra_mtnview at sbcglobal.net
Tue Apr 7 05:50:47 CEST 2009

    (I see I missed shifting my post to text, so it is hung up with the
    moderator. This is in text format.)

Digging around hasn't been very successful; however, with your 
suggestion above to look for images and drawing in Wiki-land may pay off.

Drawing on top of an image doesn't seem like it's going to help much if 
I want the user to move the circle-crosshair with his mouse. In some 
ways this is kind of standard stuff found in programs like PaintShopPro, 
and PhotoShop. The ideas are the same as PIL in that layers correspond 
to a PIL modes, and bands are sub-layers that contain R,B,G, A. In PSP, 
one piles a transparency on top of another layer. In PIL land it seems 
like, according to the example, one pastes into the layer. Somehow I 
doubt that's the way it works. I would think they get stacked on top of 
one another, so they could slide easily if required by a mouse. It could 
go either way depending on use.

Something that may be instructive on these needs is Grayson's book on 
Tkinter, which has a few chapters on the web. He provides all the 
examples, and one chapter of his book is a drawing program that uses 
rubberband effects, and moving objects on the canvas--maybe even IP 
work. I think I will shortly fire up the drawing program, after I locate 
the Pmw toolkit, which he likes to use.

As for xpPython, I know little about it. I'm working with a 2000+ line 
program written by someone else that uses Tkinter. I'm adding new 
features to it, and  not so sure it's wise to go off onto some other 
form of Python or toolkits without understanding what I've really got. I 
had not used Tkinter until 2 months ago, when I began this effort, and 
only have about 3 months of Python experience. However, I have plenty of 
programming experience in days of yore. A few weeks ago I bought Core 
Python and the author has a few pages on it, but doesn't make much of a 
case for it. He says though, "The best part of all is that wxWidgets use 
the native GUI on each platform, so your program will have the same 
loo-and-feel as the other applications on your desktop."  That doesn't 
send me running for wxPython.

Christopher Barker wrote:
> Wayne Watson wrote:
>> So far I've used Python with Tkinter, and a touch of PIL. I'm pretty 
>> bound by Tkinter, since I'm modifying a program that used it quite a 
>> bit for the GUI ability rather than analysis of images with IP (image 
>> processing).
> OK, then dig around in the Tk docs and examples you can find.
> In any case, what I'm suggesting is that you don't need any fancy 
> transparency in PIL -- you simply draw your image onto the screen 
> (probaly add it to the Tk Canvas), then you draw your circle with the 
> cross-hair on top of it, using Tk -- you aren't changing your image, 
> so you can get it back by re-drawing it, or just removing the cross hair.
> -Chris


           Wayne Watson (Watson Adventures, Prop., Nevada City, CA)

             (121.01 Deg. W, 39.26 Deg. N) GMT-8 hr std. time)****

          "Less than all cannot satisfy Man." -- William Blake

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