One of the favorite image editors on the Mac is now available for iPad and it's loaded with photo tools, effects, and templates designed for almost any photo project.
Choose your effect from one of several categories, then adjust by dragging the anchors onscreen.
Each of the drawing tools has several options with many different styles.
Use the presets or slider for a quick color correction or adjust brightness, contrast, and saturation individually.
You can use Pixelmator's proprietary format, common image formats, or export to continue working in Photoshop.
Just like Photoshop, you'll get several selection tools for precise masks and adjustments.