如何将 Python tkinter canvas postscript 文件转换为 PIL 可读的图像文件?

问题描述

所以我在我的程序中创建了一个函数，允许用户将他/她在 Turtle 画布上绘制的任何内容保存为带有他/她自己名字的 Postscript 文件.但是，根据 Postscript 文件的性质，有些颜色不会出现在输出中，而且 Postscript 文件也不会在其他一些平台上打开.所以我决定将 postscript 文件保存为 JPEG 图像，因为 JPEG 文件应该能够在许多平台上打开，希望可以显示画布的所有颜色，并且它应该具有比 postscript 文件更高的分辨率.因此，为此，我尝试使用 PIL 在我的保存功能中执行以下操作:

So I have created a function in my program that allows the user to save whatever he/she draws on the Turtle canvas as a Postscript file with his/her own name. However, there have been issues with some colors not appearing in the output as per the nature of Postscript files, and also, Postscript files just won't open on some other platforms. So I have decided to save the postscript file as a JPEG image since the JPEG file should be able to be opened on many platforms, can hopefully display all the colors of the canvas, and it should have a higher resolution than the postscript file. So, to do that, I have tried, using the PIL, the following in my save function:

def savefirst():
    cnv = getscreen().getcanvas() 
    global hen
    fev = cnv.postscript(file = 'InitialFile.ps', colormode = 'color')
    hen = filedialog.asksaveasfilename(defaultextension = '.jpg')
    im = Image.open(fev)
    print(im)
    im.save(hen + '.jpg')

但是，每当我运行它时，我都会收到此错误:

However, whenever I run this, I get this error:

line 2391, in savefirst
    im = Image.open(fev)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/PIL/Image.py", line 2263, in open
    fp = io.BytesIO(fp.read())
AttributeError: 'str' object has no attribute 'read'

显然它无法读取 postscript 文件，因为它 不是，据我所知，它本身就是一个图像，因此必须首先将其转换为图像，然后作为图像读取，然后然后最后转换并保存为JPEG文件.问题是，我如何能够首先将 postscript 文件 转换为 图像文件 在可能使用 Python 图像库的程序内部?环顾 SO 和 Google 没有任何帮助，因此非常感谢 SO 用户的任何帮助！

Apparently it cannot read the postscript file since it's not, according to what I know, an image in itself, so it has to first be converted into an image, THEN read as an image, and then finally converted and saved as a JPEG file. The question is, how would I be able to first convert the postscript file to an image file INSIDE the program possibly using the Python Imaging Library? Looking around SO and Google has been no help, so any help from the SO users is greatly appreciated!

遵循 unubuntu 的 建议，我现在有这个用于我的保存功能:

Following unubuntu's advice, I have now have this for my save function:

def savefirst():
    cnv = getscreen().getcanvas() 
    global hen
    ps = cnv.postscript(colormode = 'color')
    hen = filedialog.asksaveasfilename(defaultextension = '.jpg')
    im = Image.open(io.BytesIO(ps.encode('utf-8')))
    im.save(hen + '.jpg')

但是，现在每当我运行它时，我都会收到此错误:

However, now whenever I run that, I get this error:

line 2395, in savefirst
    im.save(hen + '.jpg')
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/PIL/Image.py", line 1646, in save
    self.load()
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/PIL/EpsImagePlugin.py", line 337, in load
    self.im = Ghostscript(self.tile, self.size, self.fp, scale)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/PIL/EpsImagePlugin.py", line 143, in Ghostscript
    stdout=subprocess.PIPE)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/subprocess.py", line 950, in __init__
    restore_signals, start_new_session)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/subprocess.py", line 1544, in _execute_child
    raise child_exception_type(errno_num, err_msg)
FileNotFoundError: [Errno 2] No such file or directory: 'gs'

什么是 'gs'?为什么我现在会收到此错误?

What is 'gs' and why am I getting this error now?

推荐答案

如果您在调用 cnv.postscript 时不提供文件参数，则cnv.postscript 将 PostScript 作为(unicode)字符串返回.然后，您可以将 unicode 转换为字节并将其提供给 io.BytesIO 并将其提供给 Image.open.Image.open 可以接受任何实现 read、seek 和 tell 方法的类文件对象作为其第一个参数.

If you don't supply the file parameter in the call to cnv.postscript, then a cnv.postscript returns the PostScript as a (unicode) string. You can then convert the unicode to bytes and feed that to io.BytesIO and feed that to Image.open. Image.open can accept as its first argument any file-like object that implements read, seek and tell methods.

import io
def savefirst():
    cnv = getscreen().getcanvas() 
    global hen
    ps = cnv.postscript(colormode = 'color')
    hen = filedialog.asksaveasfilename(defaultextension = '.jpg')
    im = Image.open(io.BytesIO(ps.encode('utf-8')))
    im.save(hen + '.jpg')

<小时>

例如，大量借用 A.罗达斯的代码,

import Tkinter as tk
import subprocess
import os
import io
from PIL import Image

class App(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.line_start = None
        self.canvas = tk.Canvas(self, width=300, height=300, bg="white")
        self.canvas.bind("<Button-1>", lambda e: self.draw(e.x, e.y))
        self.button = tk.Button(self, text="save",
                                command=self.save)
        self.canvas.pack()
        self.button.pack(pady=10)

    def draw(self, x, y):
        if self.line_start:
            x_origin, y_origin = self.line_start
            self.canvas.create_line(x_origin, y_origin, x, y)
        self.line_start = x, y

    def save(self):
        ps = self.canvas.postscript(colormode='color')
        img = Image.open(io.BytesIO(ps.encode('utf-8')))
        img.save('/tmp/test.jpg')

app = App()
app.mainloop()

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