Comment 1 for bug 1274810

The Enhance operation merely adjusts the photo's color settings using heuristics. That is, there's nothing in the database today that says "these color settings were from Enhance". The user could, for example, press Enhance and then manually adjust the colors and there's no way to know (without running the Enhance algorithm again and comparing results, which is time-consuming). In this state, if the user presses Enhance again, Shotwell will reset the colors to its own enhance algorithm's results.

One way to achieve this ticket's goal would be to store the color adjustments and include a new flag in the photo's transformation settings which says, in effect, "these color adjustments are from Enhance". If the user manually adjusts the colors or resets to original, the flag is reset. The Enhance button would work its magic only if the flag is clear, otherwise it resets to original colors.