Q:

Transform SPOT5 images to natural color images

We're currently using PixelSense to convert raw SPOT5 images to natural color ones for display and printing. Do you know a good algorithm to perform the same task as we want to ingest raw images in an image server and provide an image service with on the fly natural color conversion.

A:

An option is to perform these steps:

generate a synthetic blue channel
balance the colors by outlier removal through analysing the channel historgrams. For a GPL'ed approach, see here
then create the RGB composite

Concerning the generating of a synthetic blue channel:
Since I don't have SPOT5 data here, I cannot make a test. But I found this formula (Knudsen):
Blue_synth = 0.70 × Green + 0.24 × Red - 0.14 × NIR

