Markus: GX Developer provides the ITR class for image-colour transforms. These objects simply map colours to ranges of values. The mapping can be controlled by using histograms of your data items, and then specifying a transform - e.g. Linear, Log, Equal-Area or Log-Linear. You can set the number of ranges yourself and even specify the zones individually.
I would assume when you mention vectors you intend to colour them based on the amplitudes, not the directions? If so, then you can use the ST (Statistics) class to get histogram and statistical info before creating the ITR. If, however you are using some combination of direction and amplitude, yes you will have to determine some way to relate the arrow parameters to a range of real values before you can create a colour transform. Integer values can be mapped exactly by specifying a linear transform with breaks "between" whole values, such as -.5, .5, 1.5, 2.5, etc. Geosoft color objects are limited to 256 colours - there doesn't seem to be much demand for more than this! Geosoft contouring works on gridded (equal-spaced) data. However, we have a number of different algorithms for creating grids, including a TIN-based gridding using both linear interpolation over Voronoi cells, and natural-neighbour interpolation. See the TIN class for details. For information on the above classes and all the other GX Developer classes, see the *.gxh files in your oasismontaj\gxdev\gxh directory. Be sure to read the GX Developer manual PDF file in the oasismontaj\hlp directory. I see from you "tag" line you read the Daily Onion. Stephen Cheesman _______________ Geosoft Inc. Stephen Cheesman [EMAIL PROTECTED] (905) 315-8207 Software and services for effective earth science decision-making. Free Oasis montaj interface now available at http://www.geosoft.com -----Original Message----- From: Markus Svilans [mailto:[EMAIL PROTECTED]] Sent: August 27, 2002 12:31 PM To: GXNet Subject: [gxnet]: Colour tables and GXs Hi, I have a question regarding the use of colour tables by GeoSoft programs. First I will describe what I hope to be able to accomplish in a GX I plan to develop. (A little bit of background info: I was hired by my company to develop some prototype software which visualizes vector data. The next goal is to get the software to inter-operate with GeoSoft programs to some degree, since apparently everyone in geophysics uses GeoSoft.) I understand the basics of using colour tables from reading the colour table PDF on the GeoSoft web site. The way I understand, colour tables are used to colour code purely scalar data (like total magnetic field strength, elevation, etc.). However my software colour codes vectors (non-scalar values), and plots them on a map. I therefore foresee some difficulty in writing a GX which could run inside OASISmontaj to display this data in the same way my program does. I had the following idea which I want to attempt to work around this problem. This is where I need advice. I would write a GX which requires as input a text file containing the two-component vectors. The GX would sort the vectors into "bins", where all vectors in a bin are approximately equal. The number of bins is finite; we can thus assign a numeric (integer) index to each one. The GX would write these integers into a GeoSoft grid so that they can be plotted on a map. (I am basically trying "scalarize" the vectors so that they can be colour-coded using GeoSoft's one dimensional colour tables.) A special colour table would then be used to assign colours to all of the bin indeces in the grid when they are plotted on a map. However, I am not sure of the following: Can GeoSoft contour data using Voronoi polygons? That would seem to be the most fitting method for this data because the values being plotted are integer values (the bin indeces) therefore smooth interpolation wouldn't do. Can integer data values be mapped to specific colours in a colour table, as I would need to do? What is the maximum number of colours that can be stored in a colour table? In the OASISmontaj colour table directory, I haven't been able to find one with more than 256 colours. I'm hoping to store about 5000. I would like to add that I have never written a GX before, and that I am rather unfamiliar with the usage of GeoSoft's products. I have the free OASISmontaj interface installed, and for now that will be all I can play with, because the other software is so damn expensive :). However I am an experienced programmer (mostly in C++ and various mutations of Basic) so please don't hesitate to get into specifics about code and stuff like that. Any help, hints, insights and bits of wisdom will be greatly appreciated. Thanks, Markus. -- Markus Svilans <[EMAIL PROTECTED]> Programmer and Geological Technician at Bedrock Research Corp. "Archduke Discovered Alive: Great War Fought in Vain" _______________________________________________________ More mailing list info http://www.geosoft.com/support/listserv/index.html _______________________________________________________ More mailing list info http://www.geosoft.com/support/listserv/index.html
