RealTexture Tools Pictorial Demo

Color Correction

The first image above is a scan of a photograph of grass. In the second image, the color of the grass has been changed with CGSD's Color Correction tool. The user selects an input color in the original photo and a target color they would like their input changed to. The tool automatically finds all colors in the image similar to the input color and changes them to a corresponding shade of the target color. In this example, the tool also changed the overall brightness of the image to correspond to the disparity between input and target colors. This calibration is often necessary when images come from photographic prints, slides or PhotoCD.

In older versions of Photoshop, the user would have to select colors with repeated "shift-clicks" of the magic wand, but still have no way to replace many shades of the selected color. The new version of Photoshop, (3.0.4), offers similar functionality with its color replacement tool, but can not calibrate an entire image based on the selection of a known color, and can only replace one color at a time.

The Color Correction tool has multiple methods of calibrating image lightness by recognizing a known color in the image. User's can adjust the overall lightness of an image based upon the measured disparity between the known target color, and the corresponding input color in the image. Calibration and replacement can be based on a single color choice, or by selecting up to ten colors at once. The known target colors can be chosen from an included library of over 350 colors that were accurately measured from real-world sources. (See below for more information.)

In this example, the Color Correction tool shows its ability to ignore colors that aren't selected in the correction process. Here the change in green of the palm leaves is very slight. The overall brightness of the image has not been changed in this example, but the user always has the option.

Above is a blowup that more clearly shows the color change.

Note: displaying correct colors on the WWW is not yet a science so viewers with 8 bit displays or different gamma correction may not see the effects described.

Over 350 Real-World Color Measurements Included

Color changes are meant to be precise and the Color Correction Tool comes with a library of over 350 colors measured from real world sources with Minolta colormetric equipment. These colors include natural colors like oak tree leaves, different types of grass, samples of rock, sky, water, snow and manmade surfaces like brick, concrete, old and new pavement, etc. For imaging professionals, the library also includes standard palettes such as MacBeth.

The color measurements were made on bright sunny days on surfaces perpendicular to the sun. Because colors do not always appear this way in images, all colors can be easily recalibrated for accuracy on surfaces angled away from the sun, in shade, or even in overlighted conditions when the user may want a brighter, more exaggerated representation.

The color library is built into the Color Correction tool so access is a snap. This color library is also accessible from the Synthesis tool, also contained in the tool set.

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