[cups] cups Digest, Vol 37, Issue 2

[Alan Corey]

icm files are like TIFF files with a header, internal directory
structure, an endianness independent of the operating system.  Most of
it is mac-endian.  In a printer icm I see these tags:

#       esig    isig    offset  size
0       desc    mluc    300     178
1       wtpt    XYZ     480     20
2       bkpt    XYZ     500     20
3       chad    sf32    520     44
4       cprt    mluc    564     72
5       A2B0    mAB     636     558608
6       A2B1    mAB     559244  558608
7       A2B2    mAB     1117852 558608
8       B2A0    mBA     1676460 344976
9       B2A1    mBA     2021436 344976
10      B2A2    mBA     2366412 344976
11      gamt    mBA     2711388 104744
12      DEVS    MSBN    2816132 692668
13      targ    text    3508800 79704

In a display icm I see these tags:

#       esig    isig    offset  size
0       desc    desc    288     153
1       chad    sf32    444     44
2       cprt    text    488     31
3       rXYZ    XYZ     520     20
4       gXYZ    XYZ     540     20
5       bXYZ    XYZ     560     20
6       wtpt    XYZ     580     20
7       lumi    XYZ     600     20
8       rTRC    curv    620     16
9       gTRC    curv    636     16
10      bTRC    curv    652     16
11      vcgt    vcgt    668     1583
12      targ    text    2252    27043

I'm working on writing handlers for each type of tag because inside
each there's another structure, like the first 4 bytes are a
signature, next 4 blank, then data starts.

A BA curve is the inverse of an AB curve, that is applying it undoes
what an AB does.  I'm not sure why there's more than 1 set.  I
extracted some as tab-delimiited data and fed them through Gnuplot,
they look like this:
http://ab1jx.1apps.com/misc/test_all_a_lines.gif

The colors are just the colors assigned by Gnuplot, not related to RGB
or CMYK colors.  Notice I plot 6 data sets and get 3 lines, so 3 of
them exactly overlay 3 others.  And there are some AB and some BA
here.  The numbers are 16 bit unsigneds.  But I'm getting curves like
I'd expect.
-- 
Credit is the root of all evil.  - AB1JX