an enigma with "-size"

Hello!
First I want to thank you Gabe Schaffer and Anthony Thyssen
for help to 
choose proper Imagemagick's version.

I've got another question. I'm working for website which
converts 
thousands of pictures (about 40k) per day. We chose IM for
managing of 
conversions. We noticed, that the most time is taken by
resize of 
pictures. We made some test and:

convert a.jpg -resize 200x b.jpg
vs.
convert -size 200x a.jpg -resize 200x b.jpg

(notabene: a.jpg is a large picture)
the second one is 10 times quicker than first. Could anyone
explain that 
and using -size, please.

Or.. what are possibilities for time optimizing for resize
down pictures .

Thank You in advance.

-- 
Paweł Wolański
Medousa sp z o.o. www: http://www.medousa.pl
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=?ISO-8859-2?Q?pawe=B3_wola=F1ski?= on  wrote...
| Hello!
| First I want to thank you Gabe Schaffer and Anthony
Thyssen for help to 
| choose proper Imagemagick's version.
| 
| I've got another question. I'm working for website which
converts 
| thousands of pictures (about 40k) per day. We chose IM for
managing of 
| conversions. We noticed, that the most time is taken by
resize of 
| pictures. We made some test and:
| 
| convert a.jpg -resize 200x b.jpg
| vs.
| convert -size 200x a.jpg -resize 200x b.jpg
| 
| (notabene: a.jpg is a large picture)
| the second one is 10 times quicker than first. Could
anyone explain that 
| and using -size, please.
| 
| Or.. what are possibilities for time optimizing for resize
down pictures .
| 
| Thank You in advance.
| 
The -size is used to give a hint to the JPEG library as to
how much of
the image data should be read from the image.  the library
will return
an image usally between the size given and that size with
double the
dimensions,  in your case it probably reads in an image
256x256 in size.

As this is much smaller, IM does not need to do as much
processing to
correctly resize the image.  It is equivelent to a 'pixel'
filter resize
where lines and rows from the original image has been
junked.

I recomend you make the hint at least twice as large as the
final image
size so that Im at least has a good amount of data to
generate a
reasonable result.

The -size setting is only used for JPEG format (and image
creation).

For more info see IM examples
  Reading JPEG Images
     ht
tp://www.imagemagick.org/Usage/formats/#jpg_read
  General Thumbnail Creation
     http://www.imagemagick.org/Usage/thumbnails/#creation


  Anthony Thyssen ( System Programmer )    <A.Thyssengriffith.edu.au>
 -----------------------------------------------------------
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           "   ``   '   `   "   `'    ""
   (Random Quotes)
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     Anthony's Home is his Castle     http://www.cit.gu.
edu.au/~anthony/
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