Online photo editing has just taken a significant step closer to its computer-based predecessors: Picnik has added a curves editing feature.
Curves, one of the early killer features that drew people to Adobe Systems' Photoshop, lets people adjust in detail the distribution of light and dark tones in photographs. For example, it can be used to bring details out of shadowy murk or carefully increase contrast.
I didn't try out the feature: curves editing is reserved for those with premium accounts, which cost $24.95 a year. But it looks like it can edit red, green, and blue channels separately.