I'm a little late to the party, but this may help others.
Photoshop has the ability to read/write 'raw' format files. On opening the file you have to tell it how large the header is, if there is one, plus the dimensions, number of bands, and band layout (interleaved or no). GDAL can read/write the ENVI file format, which is essentially a raw file with a separate header file.
In a nutshell, get your image in ENVI format, rename the .env file to .raw, then open it in Photoshop. You can get the necessary info from the header file (.hdr) or the output from gdalinfo or the likes. Make your changes in Photoshop and save as a new .raw file, making sure to double-check the settings (band interleaving may get turned on by default, I can't remember). Rename the .raw to .env and do your processing with GDAL.
If you become familiar with the ENVI header files, you can manually create one for any raw file you save from Photoshop; you just have to fill in the proper details.
I do this all the time for very large (~80gb) geospatial image files. Heck, I do it for small files too, because it's a very easy way to keep your geo-information intact.