This is good information, thanks. I don't think jpeg in tiff was an
option when I did this some years ago, but if is clearly a good trick if
you can deal with the lossiness of jpeg compression.
-SteveW
On 3/22/2012 4:03 AM, Rahkonen Jukka wrote:
Stephen Woodbridge wrote:
On 3/21/2012 11:18 PM, Ian Walberg wrote:
Folks,
We are using tif format images and getting good map rendering
performance.
However the image file size could do with reducing a little.
Anyone got experience of what compression options we have
that have the
least impact on performance?
My experience of working with USGS DOQQ satellite imagery in GeoTiff
files, was that the amount of compression really did not make a
significant reduction in size. We used internally tiled tiff
files with
overviews and had over 15TB of imagery online. There are
other formats
that provide higher compression rates like MrSID and others, but
depending on the format the behavior characteristics vary
greatly and I
do not have any recent stats or comparisons of size versus
performance
versus format.
Hi,
I took numbers from one of our orthoimage set
Uncompressed tiff files from the contractor
667 File(s) 289 260 585 944 bytes
What we have on server disk after running
gdal_translate -co COMPRESS=JPEG -co PHOTOMETRIC=YCBCR
667 File(s) 21 411 672 702 bytes
Reduction in size 93%. Aerial images are used for on-screen interpretation and
difference in quality is not visible with bare eyes. The rate of the JPEG
compression can be adjusted but I have been happy with GDAL defaults. Overviews
seem to add about 40-50% to JPEG compressed images. Those I have created
probably as
gdaladdo -ro --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR
--config INTERLEAVE_OVERVIEW PIXEL tiff.tif 2 4 8 16 32 64
We have also JPEG2000 versions of the images but GDAL does not handle them as
fast as JPEG-in-TIFF files. A few years ago the speed with JPEG2000 (with
EWCJP2 and KAKJP2 drivers) was about the half of what we got with tiffs. Those
numbers are nothing to rely on today because the software versions have changed
so many times. Because of the unfriendly licenses of the good JPEG2000
libraries and because jpeg-in-tiff works so well I have not bothered to repeat
the tests myself lately. Generally, for this kind of questions the best answer
is achieved by making a well controlled test in your own environment. You can
then publish your results and tell how you did the test so that others can
check if something has been were poorly configured. For example it is not at
all the same how JPEG2000 images have been compressed and JPEG compressed tiffs
without tiles will for sure be a fiasco.
-Jukka Rahkonen-
_______________________________________________
mapserver-users mailing list
mapserver-users@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/mapserver-users
_______________________________________________
mapserver-users mailing list
mapserver-users@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/mapserver-users
