How can I convert canvas content to an image?
Question:
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?
Answers:
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()
I have found a great way of doing this which is really helpful. For it, you need the PIL module. Here is the code:
from PIL import ImageGrab
def getter(widget):
x=root.winfo_rootx()+widget.winfo_x()
y=root.winfo_rooty()+widget.winfo_y()
x1=x+widget.winfo_width()
y1=y+widget.winfo_height()
ImageGrab.grab().crop((x,y,x1,y1)).save("file path here")
What this does is you pass a widget name into the function. The command root.winfo_rootx() and the root.winfo_rooty() get the pixel position of the top left of the overall root window.
Then, the widget.winfo_x() and widget.winfo_y() are added to, basically just get the pixel coordinate of the top left hand pixel of the widget which you want to capture (at pixels (x,y) of your screen).
I then find the (x1,y1) which is the bottom left pixel of the widget. The ImageGrab.grab() makes a printscreen, and I then crop it to only get the bit containing the widget. Although not perfect, and won’t make the best possible image, this is a great tool for just getting a image of any widget and saving it.
If you have any questions, post a comment! Hope this helped!
Use Pillow to convert from Postscript to PNG
from PIL import Image
def save_as_png(canvas,fileName):
# save postscipt image
canvas.postscript(file = fileName + '.eps')
# use PIL to convert to PNG
img = Image.open(fileName + '.eps')
img.save(fileName + '.png', 'png')
Maybe you can try to use widget_winfo_id to get the HWND of the canvas.
import win32gui
from PIL import ImageGrab
HWND = canvas.winfo_id() # get the handle of the canvas
rect = win32gui.GetWindowRect(HWND) # get the coordinate of the canvas
im = ImageGrab.grab(rect) # get image of the current location
A better way for @B.Jenkins’s answer that doesn’t need a reference to the root object:
from PIL import ImageGrab
def save_widget_as_image(widget, file_name):
ImageGrab.grab(bbox=(
widget.winfo_rootx(),
widget.winfo_rooty(),
widget.winfo_rootx() + widget.winfo_width(),
widget.winfo_rooty() + widget.winfo_height()
)).save(file_name)
On my system had serious issues with ghostscript and the ImageGrab in general. Solution draw on PIL Image, save as a file, load file on PhotoImage, which is used to create new TKinter Canvas.
canvas = Canvas(win, width=IMG_W, height=IMG_H)
img = PILImg.new("RGB", (IMG_W, IMG_H), "#000")
draw = ImageDraw.Draw(img)
draw.rectangle([x,y,w,h], fill=color, outline=border)
img.save("stock-chart.png")
copyImg = PhotoImage(file="stock-chart.png")
canvas.create_image(IMG_W_2, IMG_H_2, image=copyImg)
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?
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()
I have found a great way of doing this which is really helpful. For it, you need the PIL module. Here is the code:
from PIL import ImageGrab
def getter(widget):
x=root.winfo_rootx()+widget.winfo_x()
y=root.winfo_rooty()+widget.winfo_y()
x1=x+widget.winfo_width()
y1=y+widget.winfo_height()
ImageGrab.grab().crop((x,y,x1,y1)).save("file path here")
What this does is you pass a widget name into the function. The command root.winfo_rootx() and the root.winfo_rooty() get the pixel position of the top left of the overall root window.
Then, the widget.winfo_x() and widget.winfo_y() are added to, basically just get the pixel coordinate of the top left hand pixel of the widget which you want to capture (at pixels (x,y) of your screen).
I then find the (x1,y1) which is the bottom left pixel of the widget. The ImageGrab.grab() makes a printscreen, and I then crop it to only get the bit containing the widget. Although not perfect, and won’t make the best possible image, this is a great tool for just getting a image of any widget and saving it.
If you have any questions, post a comment! Hope this helped!
Use Pillow to convert from Postscript to PNG
from PIL import Image
def save_as_png(canvas,fileName):
# save postscipt image
canvas.postscript(file = fileName + '.eps')
# use PIL to convert to PNG
img = Image.open(fileName + '.eps')
img.save(fileName + '.png', 'png')
Maybe you can try to use widget_winfo_id to get the HWND of the canvas.
import win32gui
from PIL import ImageGrab
HWND = canvas.winfo_id() # get the handle of the canvas
rect = win32gui.GetWindowRect(HWND) # get the coordinate of the canvas
im = ImageGrab.grab(rect) # get image of the current location
A better way for @B.Jenkins’s answer that doesn’t need a reference to the root object:
from PIL import ImageGrab
def save_widget_as_image(widget, file_name):
ImageGrab.grab(bbox=(
widget.winfo_rootx(),
widget.winfo_rooty(),
widget.winfo_rootx() + widget.winfo_width(),
widget.winfo_rooty() + widget.winfo_height()
)).save(file_name)
On my system had serious issues with ghostscript and the ImageGrab in general. Solution draw on PIL Image, save as a file, load file on PhotoImage, which is used to create new TKinter Canvas.
canvas = Canvas(win, width=IMG_W, height=IMG_H)
img = PILImg.new("RGB", (IMG_W, IMG_H), "#000")
draw = ImageDraw.Draw(img)
draw.rectangle([x,y,w,h], fill=color, outline=border)
img.save("stock-chart.png")
copyImg = PhotoImage(file="stock-chart.png")
canvas.create_image(IMG_W_2, IMG_H_2, image=copyImg)