I am scaling a 32-bit floating point GeoTiff image, using the command: gdal_translate -ot Byte -of GTiff -scale -a_nodata 0 Av.MaxNDVI.2000.2009.Week.19.tif overview/week19.8bpp.tif
My understanding is that the -scale option should scale my image from: Min_value -> 0 Max_value -> 255 And everything in between is scaled linearly. After doing so, I run gdalinfo on the output week19.8bpp.tif which among the other things it spits out is the following: 1 Driver: GTiff/GeoTIFF 2 Files: week19.8bpp.tif 3 week19.8bpp.tif.aux.xml 4 Size is 28800, 9600 5 Coordinate System is: .... 6 Origin = (-10007554.677000004798174,6671703.118001982569695) 7 Pixel Size = (231.656358263958310,-231.656358263958339) 8 Metadata: 9 AREA_OR_POINT=Area 10 TIFFTAG_SOFTWARE=IMAGINE TIFF Support 11 Copyright 1991 - 1999 by ERDAS, Inc. All Rights Reserved 12 @(#)$RCSfile: etif.c $ $Revision: 1.10.1.9.1.9.2.11 $ $Date: 2004/09/15 18:42:01EDT $ 13 TIFFTAG_XRESOLUTION=1 14 TIFFTAG_YRESOLUTION=1 15 TIFFTAG_RESOLUTIONUNIT=1 (unitless) 16 Image Structure Metadata: 17 INTERLEAVE=BAND 18 Corner Coordinates: 19 Upper Left (-10007554.677, 6671703.118) (180d 0'0.00"W, 60d 0'0.00"N) ...... 20 Band 1 Block=28800x1 Type=Byte, ColorInterp=Gray 21 Min=-0.199 Max=563.324 22 Minimum=-0.199, Maximum=563.324, Mean=0.233, StdDev=0.228 23 NoData Value=0 24 Metadata: 25 STATISTICS_MINIMUM=-0.19934794306755 ..... 26 STATISTICS_HISTONUMBINS=65536 27 STATISTICS_HISTOMIN=-0.19934794306755 28 STATISTICS_HISTOMAX=563.32446289062 29 LAYER_TYPE=athematic 30 STATISTICS_HISTOBINVALUES=27|28|58|70|86|90|99|79|50|30|31|35|35|30|34|3 9|37|41|38|43|63|46|71|39553020|31 37620637| 32 12895729|6925105|5280415|4393664|3759686|3302997|2920409|2608889|2344772 |2069413|2216309|1720438|1361429|33 1252933|1197 34 673|1167295|1161275|1180804|1212838|1266437|1326368|1389520|1480545|1624 178|1825891|2039326|2224735| 35 2363030|2454439|2 36 515120|2547460|2570836|2604551|2652160|2697275|2738886| And so on. I had a few questions: 1. Am I correct that linear scaling is used (are there other options?) 2. I guess the Min and Max values (Line 21) are retained from the original dataset, but I was sort of expecting to see a Min = 0 and Max = 255. Also, why is the 65000 bin histogram retained for a 8 bit image? It seems sort of confusing that some of the Tiff Tag data appears to be updated while other stuff is just copied over from the original dataset. Is there any way to force it to throw out/update the metadata? Thanks for any information. Craig _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
