image file from MemoryStream (IronPython web service)

I used to use CPython + PIL + bottle to serve image files on my web site. I used the code below to serve the image data from the PIL memory directly.

# works well in CPython
@route('/test')
def index():
    response.set_content_type开发者_如何学编程('image/png')
    img = DrawSomePILImage()
    output = StringIO.StringIO()
    img.save(output,'PNG')
    contents = output.getvalue()
    output.close()
    return contents

Now, I need to use IronPython instead of CPython to serve image files. And I'm trying to serve the image of the Microsoft Chart Control (System.Windows.Forms.DataVisualization.Charting).

# image is broken in IronPython
@route('/test')
def index():
    response.set_content_type('image/png')
    cht = GetChartControl()
    stream = MemoryStream()
    cht.SaveImage(stream, ChartImageFormat.Png)
    contents = System.Text.ASCIIEncoding.ASCII.GetString(stream.ToArray())
    stream.Close()
    return contents

But this does not work. The served image file on the web browser is broken. Can you guys help me how to make this ironpython code work?

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It's this line:

contents = System.Text.ASCIIEncoding.ASCII.GetString(stream.ToArray()) 

In doing this, you are sending a string which is the encoded form of the bytes in the image when in reality, you just want to send the bytes.

I imagine if you change it to this:

contents = stream.ToArray()

It might work (I'm not a python guy). The idea here is to pass the bytes, not a string back to the client making the request.

---

I found an answer (or just a workaround). The str of ironpython is unicode, while str of of cpython(below 3) is not. So i removed the casting part of unicode data to WSGI compatible in Bottle framework.(line 543 of bottle.py), and return the stream data as below.

contents = ''.join([chr(v) for v in stream.ToArray()])