The image was rotated when opened with imageItem

[honestappl...@gmail.com]

Hi, I am newbie to pyqtgraph.I opened the image file with scipy.misc.imread which stored the image data into numpy array and then attached the numpy array to the imageItem. Then, I found that the image was displayed with 90 degree rotation counter-clockwise. If I used the matplotlib.imshow, the image would be displayed correctlly. Is there any difference between the imageItem and the imshow function in matplotlib?

[Luke Campagnola]

Probably the image was transposed, not rotated. PyQtGraph interprets the axes of image data as [width, height], which is the opposite of most other standards. Unfortunately this behavior must be kept for backward compatibility, but I will be adding a config option soon that will cause it to interpret axes in the opposite order. 

For now, simply transposing the image data before giving it to pyqtgraph should suffice:   pg.image( img_data.T )

This operation does not incur any performance overhead.

On Wed, Mar 5, 2014 at 7:36 PM, <honestappl...@gmail.com> wrote:

Hi, I am newbie to pyqtgraph.I opened the image file with scipy.misc.imread which stored the image data into numpy array and then attached the numpy array to the imageItem. Then, I found that the image was displayed with 90 degree rotation counter-clockwise. If I used the matplotlib.imshow, the image would be displayed correctlly. Is there any difference between the imageItem and the imshow function in matplotlib?

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[honestappl...@gmail.com]

No, it was not transposed. When I run the following code, I found the image was rotated 270 degree counter-clockwise.

self.imageItem.setImage(targetImage.T)

Perhaps I should rearrange the image data matrix.

在 2014年3月6日星期四UTC+8上午9时19分04秒，Luke Campagnola写道：

[Luke Campagnola]

On Fri, Mar 7, 2014 at 8:25 AM, <honestappl...@gmail.com> wrote:

No, it was not transposed. When I run the following code, I found the image was rotated 270 degree counter-clockwise.

self.imageItem.setImage(targetImage.T)

Perhaps I should rearrange the image data matrix.

A transpose and a vertical flip, then  (which is the same as a rotation). Try:

    self.imageItem.setImage(targetImage[:, ::-1].T)

[honestappl...@gmail.com]

Yes, thank you.

在 2014年3月7日星期五UTC+8下午11时04分55秒，Luke Campagnola写道：

[Nicolas Coquelle]

Hello Luke, 

I was wondering if this option (interpret axes in the opposite order) is available in the current pyqtgraph version. 

(Did not find in the documentation).

Thanks in advance, 

Nico.

[Vincent Le Saux]

Hi,

To my knowledge, not yet.

Vincent

[Luke Campagnola]

I am working on this currently. See:

https://github.com/campagnola/pyqtgraph/tree/image-alignment

For images it seems to work; for ROIs there are still some issues.

I also have pending PRs that add unit tests for ImageItem and ROI that need to go in before this one.

To view this discussion on the web visit https://groups.google.com/d/msgid/pyqtgraph/e17b11b1-f680-4322-870e-0c8f851b7af4%40googlegroups.com.

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