Pixelmator provides most of the photo-editing tools you would need for personal use. Unless you require industrial-strength capabilities, Pixelmator should meet your requirements.
Wide range of effects: Pixelmator offers a broad collection of selection and effects tools, from blur and distortion to sharpening and retouching.
Painting and drawing: You have lots of control over brushes and can set size, opacity, and angle, for example. The tool also supports Adobe Photoshop brushes.
Layers: Pixelmator handles layers and lets you duplicate, delete, rename, and hide layers.
Color correction: You can choose to auto-enhance an image or fine-tune it with a collection of color-correction tools.
Companion iPad and iPhone apps: Pixelmator is available on OS X and also iOS. Through iCloud, you can edit and sync images with the OS X and iOS Pixelmator apps.
Gloomy interface: The tool's interface is dark, and while some might say it looks striking, with a similar feel to Apple's Photos app for OS X, the look can also start to feel dreary.
While Pixelmator lacks Adobe Photoshop's breadth of professional-level tools, it is still a solid choice for your day-to-day image-editing tasks on the Mac.
Pixelmator is an image editor for Mac OS X that allows you to create, edit, and enhance your images. Interface designed for work with images, layers-based image editing, use over 20 tools for selecting, crop, painting, retouching, typing, measuring, and navigation. Use over 15 color correction tools, use over 50 filters, adjust image size and resolution. Transform images, layers or selections using transform tools, fill and stroke images, layers or selections, photo browser offers quick access to iPhoto Library, events, albums, smart albums, and pictures folder. Use your iSight camera to add pictures to your compositions. Includes automator actions for converting, resizing, enhancing, adding special effects, and transforming images. Image processing is powered by core image and open GL.