Cannot choose `IC=C4` with CADRG Writes

[td3447]

What is the bug?

Bug

Runtime error occurs when setting IC=C4 when using CADRG write.

Error:

RuntimeError: Only IC=NC (uncompressed), IC=C3/M3 (JPEG) and IC=C8 (JPEG2000) allowed with NITF CreateCopy method.

Steps to reproduce the issue

Info

Issue arises on both the CLI and the Python code

Python Code

import os
from osgeo import gdal

# OsGeo4W
os.environ["OSGEO4W_ROOT"] = str("C:/OSGeo4W")
# GDAL
os.environ["GDAL_DATA"] = str(os.path.join(os.environ["OSGEO4W_ROOT"], "apps/gdal/share/gdal"))

gdal.UseExceptions()

# https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/vfr/
fn = "maps/Albuquerque SEC.tif"
fo_vrt = "maps/Albuquerque SEC.vrt"
fo_dir = "maps/cadrg_test"

with gdal.Open(fn) as ds:

    vrt = gdal.Translate(
        destName=fo_vrt,
        srcDS=ds,
        options=gdal.TranslateOptions(rgbExpand="rgb")
    )

    gdal.Translate(
        destName=fo_dir,
        srcDS=vrt,
        format="NITF",
        creationOptions=[
            "PRODUCT_TYPE=CADRG",
            "SCALE=500000",
            "SERIES_CODE=TP",
            "IC=C4", # <- This causes the error
        ]
    )

CLI Command

gdal_translate -of NITF -co PRODUCT_TYPE=CADRG -co SCALE=500000 -co SERIES_CODE=TP -co IC=C4 -expand rgb "maps\Albuquerque SEC.tif" "maps\cli_test"

Versions and provenance

GDAL Version

GDAL 3.13.0 "Iowa City", released 2026/05/04 (OSGeo4W)

Python Version

Python 3.12.13 (OSGeo4W)

Operating System

Windows 11

Additional context

Could just be a logic bug, as was pointed out to my on my gis.stackexchange post.
Related to this line of code.

[rouault]

CADRG creation is documented at https://gdal.org/en/stable/drivers/raster/nitf.html#cadrg-compressed-arc-digitized-raster-graphics-write-support

It doens't require setting IC=C4. Setting PRODUCT_TYPE=CADRG implies it

[rouault]

It doens't require setting IC=C4

fix to accept it in #14710

[td3447]

Thank you for your prompt reply. I got a little confused by the wording of the docs I think. I understand to be CADRG it needs the compression, but it was worded as if other options might be available, so I was trying to be thorough.

Original wording.
C4 means Vector Quantized (VQ) compression, and is only available when PRODUCT_TYPE=CADRG.

I took that to mean C4 was available when PRODUCT_TYPE=CADRG, not that it was the only available option for that product type.

Maybe something like this could clear up the docs.

C4 denotes Vector Quantized (VQ) compression. It is exclusively supported for PRODUCT_TYPE=CADRG and is applied as the default when CADRG is selected; C4 is not available for other PRODUCT_TYPE values.