
The issue is within the file "file-uploader.js" having width and height mixed up in wrong order.
Source File:
<magento root>/vendor/magento/module-ui/view/base/web/js/form/element/file-uploader.js

Exactly same problem on Magento CE 2.1.7.
I first tough that Logo Image Width and Height fields doesn't work at all because doesn't matter what number I set logo size doesn't change, but then reading this issue I used Width for Height and vise versa and it works.
How did you change the code? How it should be according to the image above?
Thanks,
Alex
@mjoraid I created Pull Request based on your investigation. I think it will be processed faster than this issue.
@alstenconsuilting to answer your question:
How did you change the code? How should it be according to the image above?
Go to this Javascript file:
<magento root>/vendor/magento/module-ui/view/base/web/js/form/element/file-uploader.js
and switch the order of the code at line 361 & 362.
Instead of height = width, make sure it's height = height and width = width. But in the code is that it's mixed up, it's set to width = height and height = width.
Wrong Code:
file.previewWidth = img.naturalHeight;
file.previewHeight = img.naturalWidth;
Correct Code:
file.previewWidth = img.naturalWidth
file.previewHeight = img.naturalHeight;
I'm still failry new to Github, but it seems @ihor-sviziev has made a pull request to add the code to the offical implementation.
@mjoraid .
Thank you. I changed code exactly as you described and it worked.
Thanks again,
Alex
Internal ticket to track issue progress: MAGETWO-70419
@mjoraid, thank you for your report.
The issue is already fixed in 2.2.0