User Manual - pancroma

59. Image Preprocessing________________________________________________________________PANCROMA TM provides a selection of useful image preprocessing utilities.Some of these can be used as part of other PANCROMA image processingoperations. Others are offered as stand-alone utilities for general application.The current suite of preprocessing utilities is described below.Arbitrary Image ResizingPANCROMA TM provides a utility for resizing either a single or else three imagessimultaneously. The first utility is useful for pan sharpening Landsat with SPOTwhereby you need to match the SPOT panchromatic image to the Landsatsubset images. Alternatively, you can resize the three or four Landsat subsetimages. This utility is also used for gap filling images and will be described inmore detail in the subsequent Gap Filling sections.In order to use this method, load either a single grayscale file or else threeidentically sized files. Then select ‘Pre Process’ | ‘Resize Images’. Select‘Resize One Image’ to resize a single grayscale image or else ‘Resize ThreeImages’ to resize three or else ‘Resize Four Images’ to resize four. You will beprompted to enter the number of rows and columns for the new image in theResize Data Input box. You can only scale an image down, not up, so makesure that both the new Rows and new Columns are less than the originals.When you have entered the values, click ‘OK’ and the new image will bedisplayed. Save it by selecting ‘File’|’Save’ as usual and save it in one of thestandard output formats. Note that the ‘Resize Four Images’ menu selectionallows you to either rescale the image or to truncate it. Truncating may be moreconvenient in some cases where a band image needs to be altered by only onerow or column.PANCROMA TM also provides a utility to resize 28.5m resolution Landsat bandsto 30m resolution. This is often useful when gap filling. Select 'PreProcess' |'Resize Images' | 'Scale Landsat 28.5m to 30m'. The utility multiplies the rowsand columns by a factor of 28.5/30 and multiplies xScale and yScale by theinverse ratio.Histogram MatchingIf you wish to match the histograms of two images, you must first open the filesby selecting ‘File’ | ‘Open’ and select first the Reference image and then theAdjust image.IMPORTANT NOTE: Make sure that you open the files in this order.168