“复制和粘贴”python程序

Question

I'm currently trying to write a program that reads a GIF file, displays its image on the screen, then allows the user to select a rectangular portion of the image to "copy and paste", AKA to then copy the image within the rectangle and then save the result as a new GIF file. I've gotten pretty far with it, but every time I think I've figured it out is seems that a new error pops up!

# CopyAndPaste.py

# This program is designed to read a GIF file, display its image on the screen, allows the user to
# select a rectangular portion of the image to copy and paste, and then save the result as a new GIF file

import tkinter
from tkinter import *
import base64

root = Tk()

def action(canvas):
    canvas.bind("<Button-1>", xaxis)
    canvas.bind("<ButtonRelease-1>", yaxis)
    canvas.bind("<ButtonRelease-1>", box)

def xaxis(event):
    global x1, y1
    x1, y1 = (event.x - 1), (event.y - 1)
    print (x1, y1)

def yaxis(event):
    global x2, y2
    x2, y2 = (event.x + 1), (event.y + 1)
    print (x2, y2)

def box(event):
    photo = PhotoImage(file="picture.gif")
    yaxis(event)
    canvas.create_rectangle(x1,y1,x2,y2)
    for x in range(x1, x2):
        for y in range(y1, y2):
            r,g,b = getRGB(photo, x, y)
            newImage(r, g, b, x, y)

def getRGB(photo, x, y):
    value = photo.get(x, y)
    return tuple(map(int, value.split(" ")))

def newImage(r, g, b, x, y):
    picture = PhotoImage(width=x, height=y)
    picture.put("#%02x%02x%02x" % (r,g,b), (x,y))
    picture.write('new_image.gif', format='gif')

canvas = Canvas(width=500, height=250)
canvas.pack(expand=YES, fill=BOTH)
photo = PhotoImage(file="picture.gif")
canvas.create_image(0, 0, image=photo, anchor=NW)
canvas.config(cursor='cross')
action(canvas)

root.mainloop()

Answer 1

The main problem with your code is that you create a new PhotoImage for each pixel! Instead, create the PhotoImage once and just add the pixels in the double- for -loop.

def box(event):
    yaxis(event)
    canvas.create_rectangle(x1, y1, x2, y2)

    picture = PhotoImage(width=(x2-x1), height=(y2-y1))
    for x in range(x1, x2):
        for y in range(y1, y2):
            r, g, b = photo.get(x, y)
            picture.put("#%02x%02x%02x" % (r, g, b), (x-x1, y-y1))
    picture.write('new_image.gif', format='gif')

Also, the line tuple(map(int, value.split(" "))) in your getRGB function is wrong, as value is already the tuple you want to create, not a string. ¹⁾ As you can see, I just 'inlined' that part directly into the box function. Another problem was that you wrote the copied pixels to x and y , but you have to write them to x-x1 and y-y1 instead.

Update 1: ¹⁾ It seems like the return value of PhotoImage.get depends on the version of Python/Tkinter you are using. In some versions, it returns a tuple, like (41, 68, 151) , and in others, a string, like u'41 68 151' .

Update 2: As pointed out by @Oblivion, you can in fact just use the from_coords parameter of PhotoImage.write to specify the region of the picture to be saved to file. With this, the box function can be simplified as

def box(event):
    yaxis(event)
    canvas.create_rectangle(x1, y1, x2, y2)
    photo.write('new_image.gif', format='gif', from_coords=[x1, y1, x2, y2])