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[OT] scanned files are large in size




A scanned document from Canon pixma mx870 printer is significantly
larger compared to the same document scanned on a different scanner.
When I look at both the images side by side on a PC, there is no
visual difference between the two. I am trying to understand the
underlying cause and fix it if possible.

As shown below, scanned_in_office.pdf is 332Kb, scanned_on_mx870.pdf is 1.7 Mb.

% ls -al scanned_in_office.pdf scanned_on_mx870.pdf
-rw-r--r-- 1 rajulocal rajulocal  331796 Jan  1 11:54 scanned_in_office.pdf
-rw-r--r-- 1 rajulocal rajulocal 1775460 Jan  1 11:48 scanned_on_mx870.pdf

Both are are scanned at 600 dpi. The only difference I see is in bpc,
enc fields.

% pdfimages -list scanned_in_office.pdf
page   num  type   width height color comp bpc  enc interp  object ID
x-ppi y-ppi size ratio
--------------------------------------------------------------------------------------------
  1     0 image    5104  6600  gray    1   1  ccitt  no         7  0
601   600  183K 4.5%
  2     1 image    5104  6600  gray    1   1  ccitt  no        14  0
601   600  138K 3.4%

% pdfimages -list scanned_on_mx870.pdf
page   num  type   width height color comp bpc  enc interp  object ID
x-ppi y-ppi size ratio
--------------------------------------------------------------------------------------------
  1     0 image    5100  6600  gray    1   8  jpeg   no         8  0
600   600 1066K 3.2%
  2     1 image    5100  6600  gray    1   8  jpeg   no        14  0
600   600  665K 2.0%

Questions:
1) Does the large file size have anything to do with the printer
itself? Is there anything I can do (ex:- update the driver/firmware or
something)?
2) Is the difference in image sizes due to the bpc (1 vs. 8) or
encoding (ccitt vs jped) fields?
3) If yes, how to change them?

thanks
raju

-- 
Kamaraju S Kusumanchi | http://raju.shoutwiki.com/wiki/Blog