Convert Andrew Toolkit Raster Objects to PBM with atktopbm

You have got a stray Andrew Toolkit raster file and no idea what will open it, and atktopbm is the converter that turns it into a plain PBM bitmap. It ships with Netpbm 11.5.2, package version 2:11.05.02-1.1build1. Allow about ten minutes once the input file is ready. This reads the source and writes a new output file, so no elevated privileges are needed unless your chosen directories require them.

1. Check the installed command

Start by confirming which executable will run and recording its Netpbm version:

$ command -v atktopbm
/usr/bin/atktopbm
$ atktopbm --version
atktopbm: Using libnetpbm from Netpbm Version: Netpbm 11.5.2
...

The version output contains build details as well as the version line, so the exact date and packaging text may differ. The local manual page is dated 26 September 1991. That old documentation describes the format and interface; the version check tells you which implementation you are actually using.

Checkpoint: You have a readable atktopbm executable and know whether you are documenting or troubleshooting this Netpbm release.

2. Keep the source and destination separate

Choose an Andrew Toolkit raster object as the input. Substitute a real path for the example below:

$ input=/path/to/image.atk
$ output=/path/to/image.pbm
$ test -r "$input" && printf 'Input is readable\n'
Input is readable

The optional positional argument is the input file. If you omit it, atktopbm reads from standard input. The command writes the PBM image to standard output, which is why the normal file workflow uses shell redirection. The name of the input file does not prove that its contents are an Andrew Toolkit raster object, so keep the later image check in the workflow.

Do not redirect output to the same path as the input. The shell opens the destination before the program starts, so a same-file redirection can truncate the source before conversion has a chance to read it. If the destination already contains a useful PBM, choose a new name or make a deliberate backup first. Do not use sudo merely to convert a file in a directory you own.

3. Convert one raster object

Run the converter with a new destination:

$ atktopbm "$input" > "$output"
$ printf 'atktopbm exit status: %s\n' "$?"
atktopbm exit status: 0

There is normally no progress message because the image is standard output. A status of zero means the program completed its conversion. It does not tell you whether you selected the expected input or whether a viewer will display the bitmap as intended.

For a pipeline, use standard input explicitly by leaving out the positional argument:

$ cat "$input" | atktopbm > "$output"

The direct form is easier to read and avoids an unnecessary cat, but the standard-input form is useful when another program supplies the raster object. Keep diagnostics on the terminal: do not merge standard error into the image with 2>&1, because that can corrupt a binary PBM.

Checkpoint: The command returned zero and the destination is a separate file. If it returned non-zero, stop before replacing anything and inspect the input path and error message.

4. Verify the PBM header and dimensions

PBM is a bitmap format. Netpbm's raw PBM output begins with the magic number P4, followed by the width and height, then binary pixel data. Use file for a quick check:

$ file "$output"
/path/to/image.pbm: Netpbm image data, size = 8 x 4, rawbits, bitmap

Your dimensions will differ. The useful signs are that the file is recognised as Netpbm image data, it has the expected width and height, and it is not empty. You can inspect the first two header lines without asking a text tool to print the binary payload:

$ head -n 2 "$output"
P4
8 4

Stop reading after the header. A raw PBM contains binary bytes after the dimension line, so a terminal or text editor may show replacement characters or make the display difficult to interpret. Use an image viewer or another Netpbm program for visual inspection.

If file reports a different format, the output may be incomplete or you may have inspected the wrong path. Check the status and size without modifying the source:

$ stat --format='size=%s bytes path=%n' "$output"
size=12 bytes path=/path/to/image.pbm

A small bitmap can legitimately be small, so size alone is not a validity test. The header and a successful image-aware check matter together.

5. Use the interface safely in scripts

The atktopbm manual defines no command-specific options. It accepts at most the optional input file shown in the synopsis, plus common options supported by Netpbm programs. Do not assume that flags from a different image converter apply here. Check this installed command when writing a script:

$ man atktopbm
$ atktopbm --help
atktopbm: Use 'man atktopbm' for help.

For a script that must not leave a misleading destination after a failed conversion, write to a temporary file in the destination directory and move it only after verification. The move is useful because it keeps the replacement on the same filesystem:

tmp_output="${output}.new"
if atktopbm "$input" > "$tmp_output" && file "$tmp_output" | grep -q 'Netpbm image data'; then
    mv -- "$tmp_output" "$output"
else
    status=$?
    printf 'conversion or image check failed; source was kept\n' >&2
    printf 'remove the incomplete temporary file when safe: %s\n' "$tmp_output" >&2
    exit "$status"
fi

This example may replace an existing destination only at the final mv. Review the path before running it: mv changes state, and an existing file at the destination can be replaced. If conversion fails, the original destination remains and the incomplete .new file can be inspected or removed deliberately. The source raster object is not changed by atktopbm.

6. Diagnose the common failures

An error opening the input usually means the path is wrong, the file is missing, or the current user lacks read permission. Check those facts without changing permissions:

$ ls -l -- "$input"
$ test -r "$input"; printf 'readable status: %s\n' "$?"
readable status: 0

A non-zero status from the converter means the output should not be treated as a valid PBM. Do not feed it to a later image step automatically. If the output file was created by redirection, preserve it for investigation or remove it as a separate, deliberate cleanup action after checking that it is not a useful file.

If the header is valid but the image looks wrong, verify that the input really is the intended Andrew Toolkit raster object and that the dimensions reported by file match expectations. atktopbm is a format converter, not a repair tool or a general image resizer. It has no documented option for choosing a width, height, crop or output colour mode.

Done means