en Copyright 1997-2009, David W. Fanning david@dfanning.com (David Fanning) Fri, 30 Jul 2010 19:06:43 GMT david@dfanning.com (David Fanning) http://www.dfanning.com/index.html IDL Programming Tips and Examples http://www.dfanning.com/images/coyote_tips.jpg http://www.dfanning.com/index.html http://www.dfanning.com/programs/fixps.pro I've beefed up the error handling in this program that turns IDL "landscape" PostScript files into real landscape files. article 532 at dfanning.com Thu, 05 Aug 2010 03:59:32 GMT http://www.dfanning.com/programs/ncdf_file__define.pro The error handling in scientific data formats (netCDF and HDF, in particular) is brain dead. You can't catch errors, can't handle them, etc. It's best not to EVER cause one. To that end, it was possible to close an open netCDF file in this object, and then destroy the object, which also caused the object to close the netCDF file. Because it had already been closed, the NCDF_CLOSE routine throws an error. (Aaauughhh!) Anyway, fixed it so this is not possible now. article 531 at dfanning.com Thu, 05 Aug 2010 03:59:32 GMT http://www.dfanning.com/programs/dataviewer.zip There have been numerous changes to this program, including a new graphical way to edit and change the program's configuration values. The program now reads most of the passive microwave data available at the National Snow and Ice Data Center (NSIDC), including gridded ice motion data. If you get this update, you will also need the Catalyst SelectImage update and the new Coyote FSC_ColorSelect widget, both of which are described below. Note that the DataViewer is a Catalyst Library application and is also included in the Catalyst Library distribution. Both the Coyote and Catalyst Libraries are required to run the program. article 530 at dfanning.com Fri, 30 Jul 2010 19:06:43 GMT http://www.dfanning.com/programs/catalyst/source/data/scaleimage__define.pro Further efforts to handle missing data correctly in terms of the color value and color index to use in the output display image. article 529 at dfanning.com Fri, 30 Jul 2010 19:06:43 GMT http://www.dfanning.com/programs/fsc_colorselect.pro A new compound widget that allows the selection of an individual color name or a color table. The widget is designed to be compatible with FSC_Inputfield in graphical user interfaces. article 528 at dfanning.com Fri, 30 Jul 2010 19:06:43 GMT http://www.dfanning.com/programs/catalyst/source/applications/gpd_viewer.pro Fixed a problem that occurred when the user switched from a northern polar projection to a southern polar projection or visa versa. article 527 at dfanning.com Fri, 30 Jul 2010 19:06:43 GMT http://www.dfanning.com/misc_tips/fanning_hike.html Coyote interviews David Fanning about Fanning's plans to take a break from the daily IDL grind. What's next? Quien sabe! article 526 at dfanning.com Sat, 24 Jul 2010 19:59:43 GMT http://www.dfanning.com/ip_tips/logscaledbar.html It is not always obvious how to create a color bar that accurately represents the values in an image that has been stretched with a logarithmic or other transformation. This article describes one way to do so. Normally, when I write an article I'm about 90 percent sure I know what I'm talking about. My confidence level is only about 50 percent in this case, but I thought I might as well stick my neck out. The worst that could happen is that I might learn something! article 525 at dfanning.com Sat, 24 Jul 2010 15:13:59 GMT http://www.dfanning.com/ip_tips/maketransparentpng.html Transparent PNG files are often needed, for example, when you are adding data overlays to Google maps of the Earth. This article explains how to create a transparent PNG file from data that that starts off as a 24-bit color image. article 524 at dfanning.com Sat, 24 Jul 2010 05:13:30 GMT http://www.dfanning.com/programs/histoplot.pro I've tried to be a good citizen in this program and restore the input color table after I draw the histogram plot and before I exit the program. It's a good idea on a display device, but it's not such a good idea in the Z-buffer using an 8-bit graphics buffer (the default). So I changed the program so that I'm not such a good citizen in the Z-buffer. article 523 at dfanning.com Fri, 23 Jul 2010 14:10:58 GMT http://www.dfanning.com/programs/fsc_color.pro The Z-graphics buffer (since IDL 6.4) is always in DECOMPOSED=1 mode, even when using an 8-bit graphics buffer. This causes FSC_Color to think it can render colors as 24-bit values when it really can't. I've changed the program to use the buffer depth instead of the color decomposition state in the Z-buffer to select which kinds of colors to use. article 522 at dfanning.com Fri, 23 Jul 2010 14:10:58 GMT http://www.dfanning.com/programs/psfix.pro This program, which fixes IDL PostScript landscape files to be real landscape (not "seascape") files, works by creating a temporary work file in the directory pointed to by the IDL_TMPDIR environment variable. It is possible, as I found out this morning, for a user to be writing the orginal Postscript file in this directory, in which case chaos ensues. I have modified the program so that the input filename is guaranteed to be different from the temporary output filename. article 521 at dfanning.com Thu, 22 Jul 2010 17:49:08 GMT http://www.dfanning.com/programs/ncdf_data__define.pro I modified the ReadVariable method to check for zero-length dimensions before reading variables out of HDF files. A warning is issued and the program continues. article 520 at dfanning.com Wed, 21 Jul 2010 16:44:13 GMT http://www.dfanning.com/programs/catalyst/source/coordinates/ncdf_coord.pro This program opens a NCDF_File object in order to read data out of an netCDF file, but the object was never destroyed when I was finished using it. Thus, there was a memory leak and a side-effect in which an ErrorLogger file was not properly deleted. Fixed in this release. article 519 at dfanning.com Tue, 20 Jul 2010 02:20:38 GMT http://www.dfanning.com/programs/catalyst/source/data/scaleimage__define.pro There was some inconsistent usage and documentation of how to deal with missing data values in images added to this object. The documentation and code has been cleaned up to handle missing data in a straightforward and consistent way. It is now possible to use !Values.F_NAN as the missing data value. article 518 at dfanning.com Fri, 16 Jul 2010 14:25:36 GMT http://www.dfanning.com/programs/catalyst/source/graphics/textline__define.pro A call to XYOUTS to obtain the width of the output text line actually results in a draw to the display screen when using hardware fonts, resulting in the text being drawn twice in two different places on the display. This has been fixed, so that only one line of text is drawn. article 517 at dfanning.com Fri, 16 Jul 2010 14:25:36 GMT http://www.dfanning.com/programs/drawshapes.pro I have added a COMPILE_OPT option to this program to draw shape files to insure that all loop variables are long integers. article 516 at dfanning.com Tue, 06 Jul 2010 02:57:13 GMT http://www.dfanning.com/programs/catalyst/source/graphics/map_grid__define.pro More tweaking of the AUTODRAWGRID keyword and the way it works. I also added a new FORMAT keyword to allow the user the ability to format map grid labels. This required the addition of a FORMAT keyword capability to two Catalyst Utility routines: Fixed_Map_Grid and Modified_Map_Grid. article 515 at dfanning.com Tue, 06 Jul 2010 02:48:35 GMT http://www.dfanning.com/programs/catalyst/source/utilities/fixed_map_grid.pro I added a FORMAT keyword to allow map labels to use user-formatted. article 514 at dfanning.com Tue, 06 Jul 2010 02:48:35 GMT http://www.dfanning.com/programs/catalyst/source/utilities/modified_map_grid.pro I added a FORMAT keyword to allow map labels to use user-formatted. article 513 at dfanning.com Tue, 06 Jul 2010 02:48:35 GMT http://www.dfanning.com/map_tips/warpimage.html This article has been updated to illustrate an important point about warping TIFF images to a different map projection with Map_Proj_Image. Namely, that the image must be reversed in the Y direction before calling Map_Proj_Image or the resulting warped image will be incorrectly georeferenced. article 512 at dfanning.com Mon, 05 Jul 2010 21:24:16 GMT http://www.dfanning.com/misc_tips/readnews.html This article describes several alternatives for reading IDL newsgroup articles without subjecting yourself to the proliferation of spam articles that have started to appear more and more frequently in Google Groups. article 511 at dfanning.com Mon, 05 Jul 2010 21:24:16 GMT http://www.dfanning.com/reading/coyote_reading.html Three books by my new favorite author, Craig Childs. How is it I have never read a book by this eloquent desert traveller? Fascinating accounts of travel and scholarship in the desert Southwest US where I grew up. It makes me realize how little I really know about the place I lived in for most of my life. I'm ready to go back and revisit the land of my youth with fresh eyes. article 510 at dfanning.com Mon, 05 Jul 2010 21:24:16 GMT http://www.dfanning.com/programs/ctload.pro I have made a change in the way this program looks for the Brewer color table file. It now uses the Coyote Library routine Find_Resource_File to look for the file. article 509 at dfanning.com Tue, 29 Jun 2010 13:06:18 GMT http://www.dfanning.com/documents/fanning_consulting.html Need help writing an IDL application? Like to consult an IDL expert? Quality IDL programming guaranteed. Currently accepting new IDL programming and consulting opportunities. Pressure of college tuition bills guarantees proprietor will not be offended by small projects, tight deadlines, or chinzy budgets! Call today for quality IDL programming: 970-221-0438. article 046 at dfanning.com Wed, 02 Apr 2008 03:42:50 GMT http://www.dfanning.com/adventures/index.html Want to know more about Coyote? Here are stories and essays of recent adventures. article 008 at dfanning.com Wed, 02 Apr 2008 03:42:50 GMT