While opening GeoTiff tagged tiff files (example: http://www.csc.noaa.gov/crs/tcm/images/avg_fill_tif.tif ) I get this:
GDL> map = READ_TIFF('avg_fill_tif.tif,Geo=geotiff)
% MAGICK_OPEN: Magick: /home/ida/baggio/Desktop/avg_fill_tif.tif: unknown field with tag 34735 (0x87af) encountered. `TIFFReadDirectory' @ tiff.c/TIFFWarnings/703
% Execution halted at: READ_TIFF 84 /usr/local/share/gnudatalanguage/lib/read_tiff.pro
Apparently magick_open quits as soon as a warning message is issued from `TIFFReadDirectory' (is this ImageMagick or libtiff itself?)
Note that when called directly from prompt ImageMagick issues some more warning messages:
> display avg_fill_tif.tif
display: avg_fill_tif.tif: unknown field with tag 33550 (0x830e) encountered. `TIFFReadDirectory'.
display: avg_fill_tif.tif: unknown field with tag 33922 (0x8482) encountered. `TIFFReadDirectory'.
display: avg_fill_tif.tif: unknown field with tag 34735 (0x87af) encountered. `TIFFReadDirectory'.
Those messages are linked to metadata tags that are not recognized, and which are linked to GeoTiff standard. The image data itself are correctly interpreted, and the image displayed. It would be nice if gdl could not stop at this kind of warnings, as it is obvious that for the purpose of visualizing the image it is not necessary that all metadata are handled.
On top of that, it would be nice having GEOTIFF keyword implemented in READ_TIFF, that could be done (I guess) looking to the three tags:
Tag 33550: 2.000000,2.000000,0.000000
Tag 33922: 0.500000,0.500000,0.000000,703985.695935,3737741.777099,0.000000
Tag 34735: 1,1,0,4,1024,0,1,1,1025,0,1,1,3072,0,1,26917,3076,0,1,9001
(the values come from the output of tiffinfo on the sample file avg_fill_tif.tif).