The option "rescale" forces a re-scaling of the output image such that the lowest pixel value is 0 and the highest pixel value is 65535. Without this option, images will only be rescaled if the total range of values in the image is larger than 65536. Alternatively the option "clip" can be used to clip values that are above 65536 and below 0, and not touch the scaling. In case of division of almost-equal images, a rescale can enhance the contrast. For more control, the option "scale=##" can be used to scale the image by a fixed amount instead of determining the best scale factor automatically. The option "shift=##" can be used to prevent clippage of negative values by adding an offset to each pixel. By default, the shift is determined such that no values will be clipped. "clip" is equivalent to specifying "shift=0 scale=1.0"
The standard KCD file consists of a header followed by raw 16-bit unsigned data. This is called the 'u16' datatype. Alternatively the 'ccp4w' datatype can be used, which will store images in compressed form using compression routines from the CCP4 suite. The default form in which a KCD file will be written by the "collect" programs is determined by the kcddatatype configuration variable. If you want a particular program to write a different type, you can specify the "ccp4w" or "u16" options to select the output file format.
The option "writeprefix=string" tells the program that the specified string is to be put before the input file name to get the output file name. So, with a prefix of "x" and an input file "s01f001.kcd", the output will be written to "xs01f001.kcd", and with "prefix=/diska/ambi/" (note trailing slash) and a filename of "i01f0001.kcd.Z" the output will be written to "/diska/ambi/i01f0001.kcd.Z" If no writeprefix has been given, the option "write=outfilename" tells the program that the specified filename is the file to write the result. If no outputfile is specified either, each program has a built-in default.