New answers tagged rescaling
The topic of downscaling is very broad, but I think that these pages are the most complete guide to image resize: http://www.imagemagick.org/Usage/filter/ http://www.imagemagick.org/Usage/filter/nicolas/ There you can find examples and discussion about the best ways to preserve detail without introducing artifacts, from the simpler algorithms to the most ...
I have found the free waifu2x very good for upsizing images. You can try an online demo. It uses "Deep Convolutional Neural Networks" to predict what the missing image data should be. It works better for line art, but is definitely acceptable for photos.
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