如何使用CherryPy返回HTTP响应中的图像 [英] How to return an image in an HTTP response with CherryPy

问题描述

我有生成Cairo ImageSurface 的代码，我这样公开它：

I have code which generates a Cairo ImageSurface, and I expose it like so:

def preview(...):
    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
    ...
    cherrypy.response.headers['Content-Type'] = "image/png"
    return surface.get_data()
preview.exposed = True

这不起作用（浏览器报告图片有错误）。

This doesn't work (browsers report that the image has errors).

我测试过 surface.write_to_png（'test.png'）有效，但我不确定将数据转储到哪里以返回它。我猜一些像文件一样的对象？根据 pycairo文档， get_data（）返回一个缓冲区。我现在也尝试过：

I've tested that surface.write_to_png('test.png') works, but I'm not sure what to dump the data into to return it. I'm guessing some file-like object? According to the pycairo documentation, get_data() returns a buffer. I've also now tried:

tempf = os.tmpfile()
surface.write_to_png(tempf)
return tempf

此外，最好在内存中创建并保存此图像（就像我'我试图这样做）或将其作为临时文件写入磁盘并从那里提供服务？我只需要一次图像，然后就可以丢弃了。

Also, is it better to create and hold this image in memory (like I'm trying to do) or write it to disk as a temp file and serve it from there? I only need the image once, then it can be discarded.

推荐答案

添加这些导入：

from cherrypy.lib import file_generator
import StringIO

然后像这样：

def index(self):
    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
    cherrypy.response.headers['Content-Type'] = "image/png"

    buffer = StringIO.StringIO()
    surface.write_to_png(buffer)
    buffer.seek(0)

    return file_generator(buffer)

另外，如果您正在提供独立文件（即它不是网页的一部分）并且您不希望它被渲染到浏览器中，而是被视为要保存在磁盘上的文件，那么您还需要一个标题：

Additionaly, if you're serving standalone file (i.e. it's not a part of a web page) and you don't want it to be rendered into browser but rather treated as a file to save on a disk then you need one more header:

cherrypy.response.headers['Content-Disposition'] = 'attachment; filename="file.png"'

此外，它是否更好？在内存中创建并保存
这个图像（比如我正在尝试
）或者将它作为temp
文件写入磁盘并从那里提供服务？我只需
需要一次图像，然后它可以被
丢弃。

Also, is it better to create and hold this image in memory (like I'm trying to do) or write it to disk as a temp file and serve it from there? I only need the image once, then it can be discarded.

如果你想要的唯一的东西要做的是将此文件提供给浏览器，没有理由在服务器上的磁盘上创建它。恰恰相反 - 请记住，访问硬盘会带来性能损失。

If the only thing you want to do is to serve this file to a browser there is no reason to create it on a disk on the server. Quite the contrary - remember that accessing hard disk brings performance penalty.

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