Cut squares from iamge

[Krikor]

Another way, at least for this type of image:

01 - Add Alpha Channel to the layer;
02 - With the Fuzzy Select Tool, select the blue color of the image background.
This will select the initial area to be removed from the image - click the 'Delete' key;
   

03 - Use the Crop Tool, delimiting the external region that will be immediately cropped and the internal region that will be cropped to the content;
   

04 - Image - Crop to Content;
05 - Layer - Extract objects - Extract objects to layers
   

06 - Now just use a plugin or a script to export the layers generated in the previous step to a folder.


If I haven't forgotten anything... that's it!