Optimal Image resizing in TListview and TImage in iOS/Android [closed]

  

I’m asking this question specifically to Delphi as I don’t seem to be able to get more specific answers in general forums.
In my app, users normally choose 1-4MB photo (via Photo Gallery or Camera)… but it’s not practical for server to send/receive such a large photo.
Hence, resizing is needed for the server to store small thumbnails to send to end-user client (ios/android). There are quite a few resizing algorithms around.
The question is: choosing photo size vs JPG quality
Scenario:
I’ve to display the final photo in a 200w x 150h image to display (either TImage or using TListview’s Image)

If I resize the 4MB photo to 100w x 75h, from what I read, it will look blurry on retina displays.
so if TImage is 100w x 75h, is there a formula to determine what should an ideal thumbnail size be like? Example, go for 2X or 3X the dimension of the display control. Is there some guide on how to balance these trade-offs and the pros and cons of this?

Hope to hear from someone’s experience.

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