From Evident Technologies:
The Asiva Shift+Gain Plug-In for Adobe Photoshop has been called by professionals fundamentally different from anything else on the market and fundamentally more useful. It is a powerful color correction plug-in that can make sophisticated transformations trivial.
First, use Asiva's built-in Hue, Saturation and Intensity Maps to draw curves defining the source color(s) you want to correct. You may begin this process of selecting you want to correct by sampling the colors in the area of the image you wish to affect, with the built in Color Sampler Tool.
Manually adjusting the curves in the maps allows you to refine certain Hue or Saturation or Intensity values selected. You can see what you have selected by overlaying a chosen color in preview mode.
The slope of the curves will define how the filter is transitioned. A near vertical line on your Map will create defined boundaries between where the filter is applied and is not, and a gently sloped curve on the Map will make the boundaries smooth. Asiva's curves are so precise that tedious masking prior to application of the filters is often not necessary.
Then make color correction adjustments independently to each color component for RGB, CMYK, or YUV. You may fine tune your color corrections with a second pass of the filter, independently on each color component of Hue, Saturation and Intensity.
Toggle on and off the Preview Checkbox to switch back and forth from the source image and the color corrected image. Zoom-in all the way to 100% if desired, and pan around the image to see the results.
You will find that no other tool or plug-in can provide the color correction capabilties of Asiva Shift+Gain.
New Features Since Version 2.1: Asiva Shift+Gain 2.2 has replaced the HSV color space with the HSI color space. Although closely related to HSV, HSI has twice the bandwidth on the luminance or brightness channel as that of HSV. This change includes both the color space and individual channels you may operate on, and also the 3 Asiva Maps where you draw curves to specify target colors to shift or gain.
New Features Since Version 2.0: Asiva Shift+Gain 2.1 features much improved curve drawing amongst other minor fixes.
New Features Since Version 1.x: Asiva Shift+Gain 2.0 has a major overhaul since version 1.0. Certain controls have been moved to more logical locations, such as the Load and Save Preset buttons. New additions include edge-only capabilities, expansion or contraction of color-selected pixels and falloff control, opacity control, snapshot settings, quick curve settings, and the ability to overlay a specified color to see where color correction or color application will occur.