Example of conversion errors for XML to ICC to XML to ICC

[xsscx]

Maintainer Repro

Sat Jan 24 03:10:25 AM UTC 2026

Given a single XML File, test the conversion fidelity for XML to ICC to XML to ICC and Report.

Reproduction

Step 1. iccFromXml input.xml input-1.icc
Profile parsed. Profile is invalid, but saved correctly

Step 2. iccToXml input-1.icc input-1.xml
XML successfully created

Step 3. iccFromXml input-1.xml input-2.icc

Unexpected Output

iccFromXml input-1.xml input-2.icc

input-1.xml:64792: parser error : xmlSAX2Characters: huge text node
                              0.000000000000 0.000000000000 0.000000000000 0.000
    ^
input-1.xml:64792: parser error : Extra content at the end of the document
                              0.000000000000 0.000000000000 0.000000000000 0.000
                              ^

Unable to Parse 'input-1.xml'

NOTE: This is a Bug, see below next Reply

File Size

Given a single XML File of 3.3M the returned XML is 12M.

This is expected behavior. The 2.7x expansion results from calculator operations being evaluated to individual float16 values. Each calculator expression that previously generated a single output value now occupies explicit numeric storage.

ls -lah input.xml input-1.xml
-rw-rw-r-- 1 xss xss  12M Jan 24 03:08 input-1.xml
-rw-rw-r-- 1 xss xss 3.3M Jan 24 02:39 input.xml

[xsscx]

Maintainer Summary

2026-03-27 00:03:32 UTC

iccDEV v2.3.1.5+85663e4 (ASAN+UBSAN)

Profile: v5.00 NamedColorClass (nmcl)
Spectral PCS: 31-step biSpectral reflectance (400-700nm, BiSpectral 300-700nm, 41 steps)
Profile ID: 681d53eca55a99d11051f605e7a105c0

Observations

• The XML to Binary to XML round-trip is NOT semantically reversible for calculator-heavy profiles
• Original numerical intent/precision is preserved in float16
• Binary encoding according to ICC.2-2023 specification
• Data loss (calculator ops, labels) is by design -- the binary format stores evaluated values, not source expressions
• The libxml2 10MB limit is a Bug
  • Error: "xmlSAX2Characters: huge text node"
    • IccProfileXml.cpp:877 xmlReadFile(szFilename, NULL, 0)
    • IccMpeXml.cpp:2400 xmlReadFile(file.c_str(), NULL, 0)
    • Neither passes XML_PARSE_HUGE (0x80000) flag
• Potential observer label loss bug (enum mapping)
  • iccToXml maps it back to "Unknown observer"
  • (x-bar, y-bar, z-bar) is preserved

Profile Conversion Results

Numbers: PRESERVED (float32 precision, max rel err <5e-08)
Headers: PRESERVED (with expected normalization)
Tags: PRESERVED (6 tags, structurally equivalent)
Text: PRESERVED (copyright, description identical)
Spectral: PRESERVED (observer + illuminant + white point)
Calc Logic: LOST (93,600 operations evaluated to float16 values)
Observer: LOST ("CIE 1931 standard..." returned "Unknown observer")
NaN/INF: LOST (111,489 leaving 79 survivors after evaluation)
Format: CHANGED (tab to space, 8 to 12 decimal, line wrapping)

TODO

• Change to xmlReadFile(szFilename, NULL, XML_PARSE_HUGE)
• Research potential observer label loss bug (enum mapping)