Enable image area selection for non-Embed widgets

[alundgard]

For widgets that display images statically (i.e., do not afford panning and zooming interactions within an embedded viewer).

• Item Row
• Uploaded Item Row
• Item Grid
• Item Carousel
• Item Slideshow

Add an option Select image area to specify the region of interest.

Clicking Select image area opens a modal for the cropping interface. Repurpose the existing cropping interface and controls—currently used for the exhibit masthead and thumbnail images. However, unlike the masthead and thumbnail images, the blue area selector should be freeform rather than constrained to a fixed aspect ratio.

[taylor-steve]

@alundgard and/or @hudajkhan I have a question about how the Item Grid widget should work with this. That widget imposes styling on the image to constrain them to the grid. For example in #3350 if I configure a page as such:

It yields:

Did this come up in discussion around this widget? In general, what are the expectations around widgets like this? E.g., do we keep the current styling or do we need to discuss how to alter the display side of the widget(s) to better reflect what this new feature offers?

[alundgard]

@taylor-steve – @hudajkhan and I discussed this briefly. The Grid widget dynamically applies its own "cropping" and aspect ratio styles, depending on the number of images the creator selects to include in the grid. Creators must select images and order them carefully so that they appear as desired within the grid. I think we can assume the same is true of selecting image areas for this widget: creators should make their selection carefully, so they appear as desired. I would be wary of making changes to the current Grid widget styling, which could negatively affect existing exhibits.

[taylor-steve]

@alundgard That's perfect. I expected as much but I wanted to get it in the written history. Thanks!