[IPP] Question on PWG draft specification mismatch & parsing

[IPP] Question on PWG draft specification mismatch & parsing

Petrie, Glen glen.petrie at eitc.epson.com
Wed May 4 19:57:43 UTC 2011

I was looking some of the PWGR images you provided.  I expected the
sgray-8 to have 8 bits/color and 8 bits/pixel but the file shows 24
bits/pixel.  Which is correct?






From: ipp-bounces at pwg.org [mailto:ipp-bounces at pwg.org] On Behalf Of Roy
Sent: Thursday, April 28, 2011 9:47 PM
To: ipp at pwg.org; Michael Sweet
Subject: [IPP] Question on PWG draft specification mismatch & parsing


Hi Michael,


I had downloaded the sample PWGRaster files from:
http://ftp.easysw.com/pub/cups/examples/PWGRasterSamples.zip, with your
latest working draft of the PWG raster found at:
ftp://ftp.pwg.org/pub/pwg/ipp/wd/wd-ippraster10-20110327-rev.pdf. I
compared the raster files in the folders:

PWGRasterSamples\srgb-16  &

PWGRasterSamples\srgb-8, with the specs given in the draft document.


I found that neither of the directories contained files that adhered to
the draft document w.r.t parsing the header. Specifically for the value
of 'NumColors'. 



According to the draft document, bytes 420-423 need to contain
'NumColors' value, however, I found them to be zero. Are the sample
files outdated??



Based on the decode algorithm given in the draft document, I had tried
to obtain plain RGB raster data from a pwg-raster file. I had converted
the PDF document obtained here:
http://orenyomtov.com/downloads/testpage.pdf to obtain pwg-raster file
using Google cloud print. I am able to get the pwg-raster file from GCP
successfully. However, on converting the pwg-raster file to RGB data,  I
have been successful in decoding around 1/6th or so, to raster data
successfully, i.e. the top part of the page is being rendered
successfully, while the rest is not rendered.

(I use GIMP to open the output raster file in RAW mode).

I have attached a screenshot of the output file that I'm able to view
through GIMP (scaled down version).


Is my algorithm wrong? Or are the specs incorrect?




Roy Samuel | Celstream Technologies | www.celstream.com



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