Re: [Matplotlib-users] Question about imshow

[Pauli V. <pa...@ik...>]

Sun, 17 May 2009 00:15:48 -0400, Jae-Joon Lee wrote:

> On Sat, May 16, 2009 at 6:58 PM, 
> <jor...@ya...> wrote:
>>
>> Hi,
>> I want to read images and do some processing with them. While learning
>> how to do this, i.e. opening images, displaying them, transforming them
>> tu numpy arrays, etc., I came across a strange behaviour. If I open an
>> image and use imshow() to display it, it comes upside down. See this
>> thread in the numpy mailing list for more details:
>> http://thread.gmane.org/gmane.comp.python.numeric.general/30148 .
>> Someone on that list suggested to check here if this behavior was
>> correct. Is it normal that the image appears upside down? If yes, can
>> someone explain what's going on?
> 
> Note that the image may be upside down for you but may be correct for
> others. The array itself does not know about the orientation of the
> image and you have to explicitly specify this.

I think the point here is that

	img = Image('foo.png')
	imshow(img)

and

	img = Image('foo.png')
	imshow(asarray(img))

give different results, since matplotlib.image.pil_to_array functions 
differently from what PIL exposes in __array_interface__

-- 
Pauli Virtanen