Basically, I'd like to know how one (broadly, e.g., references in Win-land)
does IP (image processing) and drawing techniques such as rubber lines, and
dragging image objects across the canvas. I know there are some pretty
powerful toolkits out there, but I'd like to limit this to PIL and Tkinter.
If it can't be done with them, then I'll consider other possibilities. As a
starter, on the topic of transparencies, consider this program that I pulled
off the web and was posted in 1999. It purports to illustrate how one might
produce a transparency.
#!/usr/bin/python
# see http://mail.python.org/pipermail/python-list/1999-May/003388.html
from Tkinter import *
import Image, ImageTk
import tkFileDialog
class Transparency:
def __init__(self, parent):
self.canvas = Canvas(parent, bg='green')
self.canvas.pack()
b = Button(parent, command=self.open, text="Select graphics file")
b.pack()
def open(self):
self.canvas.delete(ALL)
filename = tkFileDialog.askopenfilename()
if filename != '':
im = Image.open(filename)
if im.mode != "RGBA":
im = Image.open(filename).convert("RGBA")
source = im.split()
R, G, B, A = 0, 1, 2, 3
mask = im.point(lambda i: i > 0 and 255) # use black as transparent
source[A].paste(mask)
im = Image.merge(im.mode, source) # build a new multiband image
self.graphic = ImageTk.PhotoImage(image=im)
self.canvas.create_image(100, 100, image=self.graphic)
if __name__ == "__main__":
root = Tk()
test = Transparency(root)
root.mainloop()
It colors the canvas green, and produces a black background. An image is
merged with the background. I tried out the program. It executes, but I
do not see where the transparency is apparent. I used a gif with a
picture of a telescope on a white background, and the result is what I
would see if I pasted the telescope and white background onto the green
canvas.
If there's something missing in my observation, I'd like to know what it is.
To further explore "drawing graphics", what roughly is the capability of
Tkinter or PIL to allow one to place a transparent layer (mode, I guess in
PIL may be roughly equivalent to a layer in tools like Photoshop) on top of
an image and then move the transparency around over the image with a mouse?
--
W. eWatson
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