Hugh, My read of this discussion [1] is that bitwise operators are not supported and we would need to add them as a GDAL extension. This is pretty easy to do: see [2]. Alternatively, bitwise operators are probably supported by the ExprTk expression parser [3] (supported by GDAL) or this pull request [4].
Dan [1] https://github.com/beltoforion/muparser/discussions/154#discussioncomment-13104418 [2] https://github.com/OSGeo/gdal/pull/13187/files [3] https://www.partow.net/programming/exprtk/ [4] https://github.com/OSGeo/gdal/pull/13470 On Wed, Dec 3, 2025 at 2:58 PM Hugh Graham via gdal-dev < [email protected]> wrote: > Hi, > > I am using VRT muparser expressions for bitwise operations when creating > masks and wanted to understand why I can't get the *bitwise & *operator > working? My current solution is to use fmod which is fine (and I think > equivalent) but using "&" would be convenient and a bit easier to read... > > To illustrate, the following file works: > > https://gist.github.com/h-a-graham/6db16e70e064ae8173f1052537c59761#file-fmask-fmodmask-vrt > > the expression used here is:"(fmod(Fmask, 16) >= 8) || (fmod(Fmask, 8) >= > 4) ? 0 : 1" > > ``` > gdal convert "/vsicurl/ > https://gist.githubusercontent.com/h-a-graham/6db16e70e064ae8173f1052537c59761/raw/c48b15852bcc7c5252cae4b906c14b9a3205a33d/fmask-fmodmask.vrt"; > "test.tif" > ``` > > However, the following file fails: > > https://gist.github.com/h-a-graham/6db16e70e064ae8173f1052537c59761#file-fmask-bitmask-vrt > the expression parsed as: "((Fmask & 8) > 0 || (Fmask & 4) > > 0) ? 0 : 1" in the XML but provided as (to my xml parser): > > "((Fmask & 8) > 0 || (Fmask & 4) > 0) ? 0 : 1" > > ``` > gdal convert "/vsicurl/ > https://gist.githubusercontent.com/h-a-graham/6db16e70e064ae8173f1052537c59761/raw/c48b15852bcc7c5252cae4b906c14b9a3205a33d/fmask-bitmask.vrt"; > "test.tif" > 0...10...20..ERROR 1: Unexpected token "& 8) > 0 || (Fmask & 4) > 0) ? 0 : > 1 " found at position 8. > ``` > > So, is using "&" possible, or should I just stick with fmod and not worry > about it? > > Any help would be much appreciated. > > Hugh > > > > > > > _______________________________________________ > gdal-dev mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/gdal-dev >
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