I use Snapseed on Android. It's a practical app with many photo editing tools
I like how I can edit my photos here,
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DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
PicsArt - Explore 100,000,000+ awesome images and photos on the web
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Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.