image size and image view aspect ratio

[kswang1029]

When we use Session.set_view_area() to configure a view area in a headless mode, it refers to the image size from session.save_rendered_view('test.png') (ie the red box in the attached figure). In practice, we better consider the view_area as the "field of view" of the image viewer (ie the green box in the attached figure). In this case, it provides users the control of the aspect ratio of the "image" in interest directly. Then users may use other tools to compose a grid of images for presentation purposes.

Is it possible to support this? This may need the support from carta-frontend? @veggiesaurus @YuHsuan-Hwang

[YuHsuan-Hwang]

@kswang1029 Yes, I think frontend now supports it. We can get the paddings from OverlayStore.paddingLeft/Right/Top/Bottom, and then call set_view_area with green box size + paddings. But we will need to resize it when overlay settings are changed (i.e. paddings changed). Also note that set_view_area includes multiple images.