pythonbitmaptkinter

How can I convert canvas content to an image?


from Tkinter import *
root = Tk()
cv = Canvas(root)
cv.create_rectangle(10,10,50,50)
cv.pack()
root.mainloop()

I want to convert canvas content to a bitmap or other image, and then do other operations, such as rotating or scaling the image, or changing its coordinates.

Bitmaps can improve efficiency to show if I am no longer drawing.

What should I do?


Solution

  • You can either generate a postscript document (to feed into some other tool: ImageMagick, Ghostscript, etc):

    from Tkinter import *
    root = Tk()
    cv = Canvas(root)
    cv.create_rectangle(10,10,50,50)
    cv.pack()
    root.mainloop()
    
    cv.update()
    cv.postscript(file="file_name.ps", colormode='color')
    
    root.mainloop()
    

    or draw the same image in parallel on PIL and on Tkinter's canvas (see: Saving a Tkinter Canvas Drawing (Python)). For example (inspired by the same article):

    from Tkinter import *
    import Image, ImageDraw
    
    width = 400
    height = 300
    center = height//2
    white = (255, 255, 255)
    green = (0,128,0)
    
    root = Tk()
    
    # Tkinter create a canvas to draw on
    cv = Canvas(root, width=width, height=height, bg='white')
    cv.pack()
    
    # PIL create an empty image and draw object to draw on
    # memory only, not visible
    image1 = Image.new("RGB", (width, height), white)
    draw = ImageDraw.Draw(image1)
    
    # do the Tkinter canvas drawings (visible)
    cv.create_line([0, center, width, center], fill='green')
    
    # do the PIL image/draw (in memory) drawings
    draw.line([0, center, width, center], green)
    
    # PIL image can be saved as .png .jpg .gif or .bmp file (among others)
    filename = "my_drawing.jpg"
    image1.save(filename)
    
    root.mainloop()