There are a lot of good photoshop alternatives. Most are better at individual use cases than photoshop. For example, nearly all the alternatives are better at designing website comps because they are object-based instead of layer-based.
There are "some" Photoshop wannabes. I still haven't found any program on Linux that can give me anywhere close to the same ease of use and powerful tools that Photoshop has. The example you provided sounds like you want to use Illustrator for your use case anyway.
