[gdal-dev] HFA (.img) driver prints Warning 1: NaN converted to INT_MAX when float raster has nan as the NoData value

Thu May 8 22:56:22 PDT 2025

Hi,

Another method to reproduce without Python by using gdal_create:

gdal_create -outsize 100 100 -ot float32 -a_nodata nan -of hfa nan.img

C:\data\000\gdaltest>gdalinfo nan.img
Warning 1: NaN converted to INT_MAX.
Driver: HFA/Erdas Imagine Images (.img)
Files: nan.img
Size is 100, 100
...
Band 1 Block=64x64 Type=Float32, ColorInterp=Undefined
  Description = Layer_1
  NoData Value=nan
  Metadata:
    LAYER_TYPE=athematic

If I convert nan.img into GeoTIFF with "gdal_translate nan.img nan.tif", I do see the warning, but the new GeoTIFF still has NoData Value=nsn. I wonder what is the real meaning of the warning.

-Jukka Rahkonen-

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Lähettäjä: gdal-dev käyttäjän Jason Roberts via gdal-dev puolesta
Lähetetty: Perjantai 9. toukokuuta 2025 2.04
Vastaanottaja: Even Rouault; gdal dev
Aihe: Re: [gdal-dev] HFA (.img) driver prints Warning 1: NaN converted to INT_MAX when float raster has nan as the NoData value

Thank you. I can help you repro it if you want to take a look.I'm having trouble attaching a .img file to email. My email system doesn't want to allow it, even if I put it in a zip. But here is a simple way to repro it by creating the file with GDAL itself. (In this example, I used float64 and the same warning occurs.) You could use this to produce a test file. If you'd prefer I send a file I can post it to a file exchange service.>>> import numpy as np>>>>>> from osgeo import gdal>>> print(gdal.__version__)3.9.2e>>> gdal.UseExceptions()>>>>>> # Create the dataset as float64 with 1 band>>> f = 'has_nans.img'>>> drv = gdal.GetDriverByName('HFA')>>> ds = drv.Create(f, 100, 100, 1, gdal.GDT_Float64)>>>>>> # Make some fake data; set some cells to nan, although this is not necessary to repro the warning>>> data = np.arange(100*100, dtype=float).reshape(100,100)>>> data[0:20,0:30] = float('nan')>>>>>> # Write the data to the band>>> band = ds.GetRasterBand(1)>>> band.SetNoDataValue(float('nan'))0>>> band.WriteArray(data, 0, 0)0>>>>>> # Close the dataset>>> del band, ds>>>>>> # Open it again - warning happens here>>> ds = gdal.Open(f, gdal.GA_ReadOnly)Warning 1: NaN converted to INT_MAX.JasonOn 5/8/25 18:39, Even Rouault wrote:There are metadata fields that the HFA driver opens. That must come from that. Always shutting down the warning could be inappropriate, but perhaps in the context where the warning is emitted the driver could avoid emitting it. But we need to have access to the file to better understand the call path.Le 09/05/2025 à 00:35, Jason Roberts a écrit :Hi Even,Thanks. I can silence this with a custom error handler (I tested it, and it works). But the part that is confusing to me, as a user of the Python API, is that I did not ask the API to do anything with int32s. All I did was open the dataset using the default parameters of gdal.Open(). I would not expect a warning to be reported in that circumstance, unless opening .img files that use nan as the NoData value was problematic for GDAL in some way. That is why I was suggesting that the warning be removed.JasonOn 5/8/25 17:51, Even Rouault wrote:Jason,It looks like something in the code asks a float64 field to be returned as a int32, and thus NaN has to be turned into something else. That's perhaps fine in the context where that happens with your file and could potentially be silenced, but access to the file would be needed to investigateEvenLe 08/05/2025 à 23:01, Jason Roberts via gdal-dev a écrit :Hi GDAL team,I'm working with the GDAL Python API. I have some HFA (.img) files that are float32 and that use nan as their NoData value. As far as I can tell, using nan is allowed but I could be wrong. When I open them, I get "Warning 1: NaN converted to INT_MAX." Everything seems to work fine after that. Is this message something I need to worry about? If not, may I suggest you remove it from the HFA driver if possible?Here's some code demonstrating the message. If need be, I can provide an example file, or write some code to generate one.>>> import numpy as np>>> from osgeo import gdal>>> gdal.__version__       # this version is packaged with ArcGIS Pro 3.4, but I don't think the version matters'3.9.2e'>>> ds = gdal.Open(r'\\conch\denmod\Covariates\NARW25\CMEMS_GLORYS\SST\1999\SST_199901.img', gdal.GA_ReadOnly)Warning 1: NaN converted to INT_MAX.>>> band = ds.GetRasterBand(1)>>> gdal.GetDataTypeName(band.DataType)'Float32'>>> band.GetNoDataValue()nan>>> arr = band.ReadAsArray()   # the data look ok:>>> np.isnan(arr).sum()86788>>> (~np.isnan(arr)).sum()142985>>> np.max(arr)nan>>> np.nanmax(arr)27.078554As far as I can tell, the warning comes from this code in gdal/frmts/hfa/hfafield.cpp:                else if (std::isnan(dfDoubleRet))                {                    CPLError(CE_Warning, CPLE_AppDefined,                             "NaN converted to INT_MAX.");                    nIntRet = nMax;                }But I don't know if there are any negative ramifications that will result.Thank you for your help. And, as always, thank you very much for developing and maintaining GDAL.Jason _______________________________________________
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