User Manual - pancroma

the ‘Pan Sharpening Pre Processing Group’ on the ‘Image Processing DataInput’ form.IMPORTANT NOTE: Histogram matching is automatically disabled if ELIN localoptimization is enabled as it is unnecessary.In addition, you can clip the histogram tails. Clipping the histogram can prevent askewed transformation as a result of a lot of purely black pixels in the collar areaof the image. It is sometimes beneficial to also clip the high tail (pure white) ifthere are a lot of saturated clouds or snow that may similarly skew the transform.The default is for a single histogram channel (histogram[0] all black pixels) to beclipped. If you wish to clip additional channels from the high and/or low tails ofthe histogram, you can adjust the sliders provided. The following figure showsthe location of the histogram match settings on the image processing data inputform.Unfortunately, histogram matching can sometimes itself create undesirableartifacts in the pan sharpened image. This is because the adjusted histogramdiffers from the reference histogram in small but important ways, and is purely aresult of the nature of the discrete transform function. In most cases thistransform function, when applied to the input histogram will yield an acceptableresult. Occasionally the transform function will produce artifacts. One of themore common artifacts is an unnatural light blue image highlight. This iscommon and can be pronounced in images where green foliage and ocean areboth present in the image. The following image shows an example of theseartifacts.57