The Align Histogram module is a useful precursor to any image comparison routines such as template matching, cross correlation, stereo depth or simple image subtraction. The module takes as input two images and will align the colors in the "source" image with those specified in the "target" image. Thus if you wish to compare images with respect to colors this module will provide a way to greatly reduce different lighting and color shift effects that can happen between two successive image captures or even in simultaneous capture by different cameras.

Interface

Instructions

1. Source - Select the source image or the image that should be transformed into the target's colors/intensity.

2. Target - Select the target image or the image that has the "right" colors/intensity. Note that if no target image is specified the source image is transformed into a standard histogram where the red, green and blue channels are normalized.

3. Overlay - If your source image has had a color remapping relative to the target in a non-linear way you may want to chose the "Align using overlap occurance count" which will compare pixels in the source and target at the exact same location and use the combination that is most frequent in the two images. Thus if a red pixel in the source image is always in the same location as a blue pixel then the source image red pixel will be mapped/converted to a blue pixel to best match the target image. This is useful in situations where you would like to compare the two images and ensure that the source is as close as possible to the target image without actually changing the pixels location.

Example

Source	Default Alignment (no target)

Target	Source	Align Histogram

 Click Here to load a robofile that was used to produce the above alignment using the source and target image. You can specify the image to align to in the Load Module within that robofile and then just drag/drop images that you want to transform into the main RoboRealm GUI interface.

See Also

Color Balance

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