The short answer is to first scale each data set to a range of 0-1 (there's reasons you may want to scale to a different range, or use weighting, but we'll save that description for the long answer). Assuming each data set has same positions, then Compute [R,G,B], where R is the data set to display red in the composite, G is data set to display green, and so on. Use the result of the Compute as your color component of the field. Simply doing Unmark 'colors' works for me, but the DX academics out there probably would do it differently (Replace 'Colors' with 'Data' ??)
Frequently in remote sensing applications, the composite looks better or gives more visual information when the brightness in the B (or R or G, I suppose) part is reversed, e.g. highest data value is scaled to lowest brightness. You may want to add this capability at the outset. You also need a way to handle invalid data if it exists in either of the 3 data sets or data parameters. On May 8, 6:24pm, José Luis Gómez Dans wrote: > Subject: [opendx-users] Colour composites? > Hi, > I was just trying to visualise some data, and came to the > conclusion that it would be nice if I could visualise 3 data sets > simultaneously. Say I have 3 images that correspond to the same scene, > each with different imaging parameters (this is very normal in remote > sensing: you have views of the same scene at, say differentfrequencies). > Since the data is overlapping, I can assign each image a basic colour > and blend them: > -image 1 has red > -image 2 has green > -image 3 has blue > > Areas that in the three images have a large value are then seen > as white, whereas areas with low values in the three images are mostly > black. Basically, you blend the colours. > > I can do this by working out RGB values and then importing that > into DX, but I was wondering whether there's a way to do this > automagically. My problem is that I am not sure of this technique's name > either. > > Any help appreciated, > José > -- > José L Gómez Dans PhD student > Tel: +44 114 222 5582 Radar & Communications Group > FAX; +44 870 132 2990 Department of Electronic Engineering > University of Sheffield UK >-- End of excerpt from José Luis Gómez Dans
