Need a way for deterministic .icc output

[bmwiedemann]

In hughsie/colord#174 we found that .icc files in the colord package vary depending on the CPU used to build them.
Is there already a way to ensure that .icc output does not depend on availability of SSE or other CPU features? Or can you add it?

This issue was found while working on reproducible builds for openSUSE.

[mm2]

After spending some time in the files, I found only CMYK profiles are affected, profiles are truly different. Black point and white points in FOGRA27 profile are different, for instance. Littlecms does NOT compute such tags in any case, it is the caller program that requests to put the values. The profile seems to be generated by argyllcms whilst lcms is used to modify it somehow. Maybe to change some metadata. It seems the issue is not on lcms side because RGB profiles dealing with exactly same tags are not affected.

[bmwiedemann]

Do you know of a (FLOSS) tool that can dump .icc info into text form (so that I can diff it)? That would greatly help debugging.

[mm2]

Unfortunately there are very few FOSS projects on ICC profiles. Maybe this one, but I cannot assure you it does what you need. https://sourceforge.net/projects/iccxml/

[ValeZAA]

Do you know of a (FLOSS) tool that can dump .icc info into text form (so that I can diff it)? That would greatly help debugging.

https://github.com/InternationalColorConsortium/iccDEV

Also

~/skcms (master|✔) $ out/clang/iccdump ~/Downloads/B156HW01\ \#1\ 2017-08-07\ 23-19\ 2.2\ F-S\ XYZLUT+MTX.icc
                Size : 0x000B4E0C : 740876
            CMM type : 0x00000000 : ''
             Version : 0x02400000 : 2.4.0
       Profile class : 0x6D6E7472 : 'mntr'
    Data color space : 0x52474220 : 'RGB '
                 PCS : 0x58595A20 : 'XYZ '
  Creation date/time :            : 2017-08-07 23:31:23
           Signature : 0x61637370 : 'acsp'
            Platform : 0x00000000 : ''
               Flags : 0x00000000
 Device manufacturer : 0x0000AE30 : ''
        Device model : 0x000040B2 : ''
   Device attributes : 0x00000000
                     : 0x00000000
    Rendering intent : 0x00000000 : 0
        Illuminant X :            : 0.964202881
        Illuminant Y :            : 1
        Illuminant Z :            : 0.824905396
             Creator : 0x00000000 : ''
           Tag count : 0x00000016 : 22

 Tag    : Type   : Size   : Offset
 ------ : ------ : ------ : --------
 'desc' : 'desc' :    138 : 396
 'cprt' : 'text' :     74 : 536
 'lumi' : 'XYZ ' :     20 : 612
 'wtpt' : 'XYZ ' :     20 : 632
 'bkpt' : 'XYZ ' :     20 : 652
 'vcgt' : 'vcgt' :   1554 : 672
 'A2B0' : 'mft2' : 227980 : 2228
 'rXYZ' : 'XYZ ' :     20 : 230208
 'gXYZ' : 'XYZ ' :     20 : 230228
 'bXYZ' : 'XYZ ' :     20 : 230248
 'rTRC' : 'curv' :    524 : 230268
 'gTRC' : 'curv' :    524 : 230792
 'bTRC' : 'curv' :    524 : 231316
 'A2B1' : 'mft2' : 227980 : 2228
 'B2A1' : 'mft2' : 241786 : 231840
 'B2A0' : 'mft2' : 241786 : 473628
 'targ' : 'text' :  23061 : 715416
 'DevD' : 'text' :  23061 : 715416
 'CIED' : 'text' :  23061 : 715416
 'chrm' : 'chrm' :     36 : 738480
 'mmod' : 'mmod' :     40 : 738516
 'meta' : 'dict' :   2320 : 738556

~TRC : 2.1826818, 1.02218008, -0.0218680613, 0.182920888, 0.0235294122, 0.00430246489, 0  (Max error: 0.00801050663)
rTRC : 16-bit table with 256 entries
gTRC : 16-bit table with 256 entries
bTRC : 16-bit table with 256 entries
 XYZ : | 0.616897583 0.204925537 0.142379761 |
       | 0.293243408 0.653274536 0.053482056 |
       | 0.008407593 0.083129883 0.733367920 |
 A2B : "A", CLUT, "B"
 "A" : 3 inputs
  A0 : 16-bit table with 2049 entries
  A1 : 16-bit table with 2049 entries
  A2 : 16-bit table with 2049 entries
CLUT : 33 x 33 x 33 (16 bpp)
 "B" : 3 outputs
  B0 : 16-bit table with 2 entries
  B1 : 16-bit table with 2 entries
  B2 : 16-bit table with 2 entries