I think Serif Affinity Photo is one of the best alternatives to Adobe Photoshop. Although it is relatively newer to the market than some other graphic design software it is an affordable, non-subscription based substitute for Windows and MAC that provides several options for image processing and creative effects. In fact, the software has thorough raw file format editing and various colour space options. It is also compatible with typical file formats, and live previews as effects are applied. Other benefits include photo stitching, new alpha and black point selections, and excellent lens corrections. Furthemore, it has a wide range of high-end filters such as lighting, blurs, shadows and tilt. Affinity Photo is remarkable for its .psd compatibility, adept handling of layers and large tool set such as mesh warps and live previews. Through operational "personas", you can edit raw files, do non-destructive modifications with layer adjustments, generate distortion effects and much more.