Batch-converting of INTA images - image-processing

Question

I have a large number of images in the INTA format, an old SGI standard. INTA is a grayscale image with an alpha channel. All of these need to be converted to TGA files. The problem is that neither ImageMagick nor PIL/Pillow seem to be able to parse them correctly. ImageMagick can read and export them but doesn't seem to understand the alpha channel, and PIL fails to open them, with the error ValueError: Unsupported SGI image mode. The one thing that I've found that reads them successfully is GIMP:
An ideal solution would be one that is easy to invoke from a script.
For reference, here is one of the images in question (the same one seen in the screenshot): https://www.dropbox.com/s/8hoppdgtuqxsy26/girder01.inta?dl=0

Answer 1

It seems GDAL is able to read your image and I converted it to a greyscale+alpha PNG using:
gdal_convert YOURIMAGE.sgi result.png
You can easily get to TGA from there.
I am assuming the batching is not an issue, but it would look something like this in bash:
mkdir -p OUTPUT
for f in *.inta ; do
gdal_translate "$f" OUTPUT/"$f"
done
I had all sorts of trouble installing GDAL on macOS so I just used docker like this:
docker run --rm -v /Users:/Users osgeo/gdal:alpine-normal-latest gdal_translate /Users/mark/Downloads/image.sgi /Users/mark/Downloads/result.png