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20021028: [Fwd: 20021026: Unidata lossless PNG compression of NOAAPORT image products (correction)]

>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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* Tom Yoksas                                             UCAR Unidata Program *
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