In an age when most everyone who uses computer deals in digital images in one way or another, most everyone should have a modern image editor, but I suspect relatively few actually do. This is how we end up with 3 MB email attachments. You need an image editor.
Acorn (“the image editor for humans”) is the first editor I go to, falling back to Photoshop only when necessary (content-aware fill: still magic), and with this update to version 4 that will be less and less often. I’ve used Acorn since 1.X and, just as some people will buy music from their favorite band without listening to it first, this is my attitude toward Gus Mueller’s work at Flying Meat. I trust it’s good.
The newest version of Acorn, version 4 (Mac app store link), adds new features like non-destructive filters and curve controls, promises (and delivers) improvements in speed and interface design. Almost anything else you’d need Acorn does with ease and style: filters, layers, rotations, masking, text tools, vector graphics, instant alpha, etc. etc. etc. On sale for $30 through the end of May, so if you find yourself needing more power working with photographs and image, that’s ridiculous cheap.