Hi:

I am having problems in getting the colours for a grabbed image
(obtained using ImageGrab under Windows).

The following code illustrates my problem:

####################################################################
# Test of colour palette returned from ImageGrab

from Tkinter import *
import ImageGrab
import Image
import os

class GUI (Frame):
    top = Tk()
    
    def __init__(self, parent=top):
        Frame.__init__(self,parent)
        self.master.title('Grab Test')
        self.Board = Canvas(self, width=200 , height=200 , bg="#FFF000")
        self.Board.pack(side=TOP, padx=10, pady=10)
        fButtons = Frame(self)
        self.bGrab = Button(fButtons, width=15, text="Grab",
command=self.grabBoard)
        self.bGrab.pack(side=LEFT, anchor=W, padx=10, pady=2)
        self.bQuit = Button(fButtons, width=15, text="Quit",
command=self.top.destroy)
        self.bQuit.pack(side=LEFT, anchor=W, padx=10, pady=2)
        fButtons.pack(side=BOTTOM, fill=X)
        self.pack()

        self.Board.create_rectangle(70, 70, 90, 90, fill='white')

    def colourinfo(self, im):
        hist = im.histogram()
        palette = im.palette
        for item in hist:
            coloursUsed = [i for i in range(len(hist)) if hist[i]]
        palettestring = palette.tostring()
        paletteUsed = [palettestring[3*i:3*i+3] for i in coloursUsed]
        print "There are %s colours in this image" %len(coloursUsed)
        print "Grabbed palette is:"
        for item in paletteUsed:
            for char in item:
                print '%x' %ord(char),
            print

    def grabBoard(self):
        x0 = self.Board.winfo_rootx()+2
        y0 = self.Board.winfo_rooty()+2
        x1 = x0 + 100
        y1 = y0 + 100
        im = ImageGrab.grab((x0, y0, x1, y1))

        im = im.convert('P')
        print "The grabbed image is in %s mode" %im.mode
        self.colourinfo(im)
        
        path = os.getcwd()
        im.save(os.path.join(path, 'mytest.gif'))

        im2 = Image.open(os.path.join(path, 'mytest.gif'))
        print "\nInformation from saved image:"
        self.colourinfo(im2)

if __name__ == "__main__":
    board = GUI()

####################################################################

Basically I grab an image and use my function colourinfo to tell me
how many colours there are and what they are.

I then save the image and call colourinfo again.

The output is as follows:

The grabbed image is in P mode
There are 6 colours in this image
Grabbed palette is:
0 1 2
3 4 5
9 a b
75 76 77
87 88 89
f4 f5 f6

Information from saved image:
There are 6 colours in this image
Grabbed palette is:
0 0 0
1 1 1
3 3 3
ff cc 0
ff ff 0
fc fc fc

As you can see, the information from the grabbed image is basically
garbage data, whereas the saved image has the correct information.

How can I get the correct data from the grabbed image without having
to save it first?

Any help would be appreciated. (Apologies if this has previously been
answered. I have posted this problem previously but must have missed
the reply)

Thanks,
Alfred Milgrom


On Wed, 4 Aug 2004 10:03:09 +0200, Fredrik Lundh <fredrik@[...].com>  wrote:
>  "gohaku" wrote:
>  
>  > I would like to know if there is a function to return an array of an
>  > Image's colormap.
>  
>  you want the colors in the palette?  here's one way to do it:
>  
>      http://article.gmane.org/gmane.comp.python.general/347330
>  
>  </F>
>  
>  
>  
>  
>  _______________________________________________
>  Image-SIG maillist  -  Image-SIG@[...].org
>  http://mail.python.org/mailman/listinfo/image-sig
> 
_______________________________________________
Image-SIG maillist  -  Image-SIG@[...].org
http://mail.python.org/mailman/listinfo/image-sig