User Manual - pancroma

the image resolution to a point whereby it is not much better than the input bandresolution.Interpolate Intensity ArrayThe problem with merging the computed intensity array with the pan array is thatthe file sizes are mismatched. As a result, only 25% of the pan pixels areadjusted by the merge and others are left unadjusted. This will result in a regular“grain” being introduced to the processed image. In order to correct this, there isan option to interpolate the adjusted image in order to smooth out the grain.Checking the ‘Interpolate Intensity Array’ check box does this.Save Settings Check BoxWhen this box is checked, your image processing settings will be retained fromone run to the next. This is a very useful feature as getting good panchromaticcolor can be an iterative process. You will often want to change one setting at atime, making smaller and smaller adjustments as you approach a pleasing colorbalance.Histogram Data GroupThese utilities at the lower right hand corner of the Pan Sharpening PreProcessing group allow you to select between non linear and linear matching andturn the histogram match algorithm on and off. In general the non-linearproduces better results but in some cases linear histogram matching performsbetter. (See subsequent section on histogram matching.) Besides enabling anddisabling histogram matching, you can also clip the tails of the histograms usingthe enable check box and the slider bars. A better histogram match cansometimes result if you remove the first channel (zero or all black pixels) from thehistogram match computation.This does not remove the black pixels from the image, only from the matchingcomputation. You can also clip bright pixels resulting from clouds or snow fromthe upper end of the histogram. The ‘Remove Highlights’ check box enables analgorithm to clean unwanted blue highlights that often result when histogrammatching images with both green vegetation and water present. When it isenabled, you can select the range of application (on the transformation function)by selecting the upper and lower divisor and multiplier integers in the drop downCombo Boxes. Remove Highlights is described in more detail in the Manualsection on Histogram Matching.165