RAYZ converts image data as necessary for display in the Image Viewer. A display conversion method is selected automatically, based on the type of image being displayed, but you can override the default method and use your own LUT file, as described in Display Conversion in chapter 6. This appendix explains how to create a LUT file that can be used in RAYZ.
A LUT file is a plain text document that lists pairs of values for each image channel in a simple table, with the input values in the first column and the output values in the second column.
The LUT file can include lookup tables for 1, 4, or 5 channels. If you use a 1-channel LUT file to display a multi-channel image, the same LUT file data is applied to all channels.
Each list of channel data in the LUT file must be separated by a line with two equals signs (==) on it, and nothing else.
A line can also be a comment, which begins with the // string (double divide char).
Within the section for each channel's data, the lines consist of two values:
<float input value> <8 bit output value>
This allows a completely general lookup table (that is, the input can be 8-bit, 16-bit, or float). The input value is converted to float, and then looked up. If there is no value specified, it uses the next lowest one, rather than interpolate a new one. This way you only need to specify 256 possible outputs, so you just specify a float value for each possible 8 bit value, and you are done.
Notice that you can have any number of values for a given channel (although having a single value is pretty useless, as it sets every input value to that single value).