>From: "Barbara Hickman" <address@hidden>
>Organization: NOAA
>Keywords: 200210181813.g9IIDJ102051 NOAAPORT GINI compress
Hi Barb,
>Do you have any similar information on the timing delays per product
>introduced with PNG?
Here are some numbers on how long it took to PNG compress a series of
GOES-East VIS images stored in McIDAS AREA files. The files all contain
1-byte images created from a single scan from 18:15Z on 28 Oct 02301 as
follows:
The largest image, stored in AREA3000, was created from the GER/GENHEM01V
dataset on the SATEPS machine with IP address 140.90.195.64:
IMGCOPY GER/GENHEM01V MYDATA/IMAGES.3000 TIME=18:15 SIZE=SAME STYPE=VISR MAG=1
-2
IMGLIST MYDATA/IMAGES.3000 FORM=EXP
Image file directory listing for:MYDATA/IMAGES
Pos Satellite/ Date Time Center Res (km) Image_Size
sensor Lat Lon Lat Lon
--- ------------- ------------ -------- ---- ---- ----- ----- ------------
3000 G-8 IMG 28 OCT 02301 18:15:00 14 72
Band: 1 0.65 um Visible - Cloud Cover 1.06 1.15 7308 x 6928
proj: 0 created: 2002302 5752 memo: RT GVAR
type:VISR cal type:BRIT
offsets: data= 2816 navigation= 256 calibration= 0 auxillary= 0
doc length: 0 cal length: 0 lev length: 0 PREFIX= 0
valcod: 0 zcor: 0 avg-smp: N
start yyddd: 2002301 start time:181515 start scan: 351
lcor: 2805 ecor: 9049 bytes per pixel: 1 ss: 70
Resolution Factors (base=1): Line= 1.0 Element= 2.0
IMGLIST: done
Each smaller image was created from the local VISR copy of GER/GENHEM01V
by blowing down by a factor of 2**n:
AREA IMGCOPY command that created AREA file
-----+---------------------------------------------------------------------
3001 IMGCOPY MYDATA/IMAGES.3000 MYDATA/IMAGES.3001 MAG=-2 -2 SIZE=SAME
3002 IMGCOPY MYDATA/IMAGES.3000 MYDATA/IMAGES.3002 MAG=-4 -4 SIZE=SAME
3003 IMGCOPY MYDATA/IMAGES.3000 MYDATA/IMAGES.3003 MAG=-8 -8 SIZE=SAME
3004 IMGCOPY MYDATA/IMAGES.3000 MYDATA/IMAGES.3004 MAG=-16 -16 SIZE=SAME
The following is a list of the times it took to compress the images
using the AREA PNG compression routine I wrote:
AREA AREA size PNG Size Time to compress (mm:ss)
-----+----------+---------+------------------------
3000 50632960 28858185 1:32
3001 12660672 7905475 0:15
3002 3167580 2124720 0:03
3003 795700 567738 0.00 (faster than 1 second)
3004 202112 151957 0.00 (faster than 1 second)
File sizes are in bytes.
The compression routine was run on a Sun E450 here in the UPC offices.
The E450 has 4 450 Mhz SPARC Ultra II processors. The compression
routine does not take advantage of multiple processors, so the
numbers should be the same for a single processor 450 Mhz Ultra
II SPARC that is not running other jobs.
You can see that the time it takes to compress images does not scale
linearly in input AREA file size.
I hope that these numbers are useful. The are, at least, interesting.
Tom
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