If you're willing to compile it, Aseprite is a great option as well.
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Check out a short teaser of the upcoming software, which unites AI, procedural and scanned approaches to materials. UPD: New info and links added.
During GDC 2018 keynote at Substance Day, Allegorithmic’s Sébastien Deguy showed a little teaser of the upcoming tool in the Substance family. It’s not a fully finished, but you can sign up for testing and start cooking (and maybe share your thoughts with 80.lv).
According to the official announcement, the tool introduces new ways of creating, managing and processing materials. It allows mixing procedural-based, hand-made, capture-based and AI-based workflows. The project has been in development for 2 years. Currently the company is looking for early adopters to check out the features and share their thoughts. You can sign up for a private beta here. The closed beta will start by the end of Q2 2018. The full release will happen at the end of 2018 or during the first months of 2019.
The images used in the video are done by Josip Vrandecic.