Thanks Even. I was actually more curious about the quality differences of jpeg2000, GDAL 1.11 vs 2.1. File size is important too, of course.
I did some further tests. For example, in GDAL 1.11.2: gdal_translate -of JP2OpenJPEG -b 1 -b 2 -b 3 -co "QUALITY=12" Kenosha.tif Kenosha_gdal1_11.jp2 compared to GDAL 2.1: gdal_translate -of JP2OpenJPEG -b 1 -b 2 -b 3 -co "QUALITY=12" -co "YCC=OFF" Kenosha.tif Kenosha_gdal2_1_ycc_off.jp2 .... produces results that are visually identical. However, simply by turning YCC=ON (the default) in GDAL 2.1 produces noticeably "better" images at higher zoom levels. gdal_translate -of JP2OpenJPEG -b 1 -b 2 -b 3 -co "QUALITY=12" -co "YCC=ON" Kenosha.tif Kenosha_gdal2_1.jp2 It's interesting to me that the simple addition of YCC=OFF can noticeably affect the visually quality of the output image. I certainly don't claim to understand the nuances of jpeg2000! If you have time/interest, my test files are here: https://uwmadison.box.com/s/xfc2f0ehwe6x6nu7chxu3ykvmk46mw85 Thanks again. -----Original Message----- From: Even Rouault [mailto:[email protected]] Sent: Wednesday, January 06, 2016 4:25 AM To: [email protected] Cc: Jim Lacy Subject: Re: [gdal-dev] GDAL 1.11 vs 2.1 and JPEG2000? Le mardi 05 janvier 2016 18:51:03, Jim Lacy a écrit : > Can anyone with knowledge of the JP2OpenJPEG driver confirm or deny > the following observation? > > I've been generating jpeg2000's in both GDAL 1.11.2 and GDAL 2.1. > With all settings the same, I've noticed the visual quality of the > images generated in GDAL 2.1 are noticeably "better." (a subjective > term, yes) > > To my eyes, in 1.11.2, -co "QUALITY=20" yields results visually > comparable to roughly -co "QUALITY=12" in GDAL 2.1. Win32 platform, > binaries from gisinternals.com. > > Are there significant improvements in the 2.1 driver that would > explain my observation? Jim, Checking the NEWS, I believe this might be related to this improvement I did in GDAL 2.0 * add YCC creation option to do RGB->YCC MCT, and turn it ON by default (#5634) And a quick test confirms it with a BMNG 21600x21600 3 bands : $ gdal_tanslate in.tif out1.jp2 -of jp2openjpeg $ gdal_tanslate in.tif out2.jp2 -of jp2openjpeg -co YCC=OFF $ ll out1.jp2 out2.jp2 -rw-r--r-- 1 even even 111977681 2016-01-06 11:07 out1.jp2 -rw-r--r-- 1 even even 151981743 2016-01-06 11:08 out2.jp2 RGB->YCC MCT conversion is a step that occurs before other processings, RGB->which tends to decrease the size of the resulting file, all other things equal. This transform is not completely lossless when using the default lossy compression (there's a lossless version that is used when using -co QUALITY=100 -co REVERSIBLE=YES), but the differences in pixel values tend to be very small between YCC=ON/OFF. Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
