LibGrid

# Color-Matching

Color-matching is the task of balancing the colors of adjacent or overlapping imagery, so that no seams arise when composed together. The matcher application in the tools directory can be applied to accomplish this task. It balances the colors of a foreground image to match the colors of a set of background images.

The tool does so by calculating a coarse grid of linear regression coefficients per-channel. The regression coefficients constitute the one linear mapping between the image and the background that exhibits the lowest linear mapping error. The tool interpolates the regression coefficients per-pixel and applies the corresponding linear transformation to each pixel. This way the color-characteristics of the background are over-imposed onto the foreground imagery.

As a welcome side effect, the color-matching tool can also be used to modify the colors of a false-color image to yield true natural looking colors. This is achieved by matching the false-color image with a [low-resolution] true-color background image.

As an example, we can create true-color Landsat images by matching the Landsat false-color pan-sharpened images (15m resolution) with a Modis true-color image (500m resolution):

grid/matcher landsat.tif modis.tif truecolor.tif