PencilSheep is a free professional image editor with full GPU acceleration, interactive filter layers, and HDR support. PencilSheep provides all the features you'd expect to find in a professional image editor, such as layers, filters, layer styles, adjustment layers, masks, selections, undo/redo, and various different tools. In addition to that, PencilSheep adds many new features, such as interactive filter layers, full HDR support, and full GPU acceleration. PencilSheep executes all performance-critical operations (blending, filters, paint tools, etc.) on the GPU. Unlike traditional image editors (which either don't use GPU computing at all, or only offer partial GPU acceleration), PencilSheep has been specifically designed from the ground up to fully utilize the GPU for all image manipulations. For many tasks, PencilSheep is orders of magnitude faster than traditional image editors.
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Pros
Pro Seems stable and light
This is an expectation though, since was not used/ tested long term.
Pro Simple to use, initiative
Pro Full set of image manipulation tools
Pro Cross platform
Cons
Con Snap only
For Linux, the choice seems to have been to offer PencilSheep as snap only, sorry, no .deb, no .rpm, no nothing. If you do not have/ use snap (for many, including valid reasons), PencilSheep is beyond your reach.
Con Project no longer supported?
Although it is offered widely (including Google), the devs website seems dead. Hence, it is unclear whether it is still developed and supported actively.