Extract a Palm Image Viewer image into PAM with pdbimgtopam

You will extract the image record from a Palm Pilot Image Viewer PDB file and write it as a PAM image that Netpbm tools can read. The command can also save the image note, if the PDB contains one. Allow about fifteen minutes: the conversion itself is quick, but checking the binary output and choosing a safe destination deserves care.

You need Linux, a readable Palm Image Viewer PDB file, and the Netpbm package. The installed command checked for this guide is Netpbm 11.5.2, built from source dated 31 March 2024. The local manual page is dated 25 September 2010, so examples below describe this installed command and its documented interface, not every historical or future Netpbm build.

1. Check that pdbimgtopam is available

Run this as your ordinary user. Conversion does not normally need elevated privileges because it only reads the input and writes files where you already have permission.

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

The installed program prints more build information after the version line. If command -v finds nothing, install Netpbm through your normal package manager before continuing. Do not use sudo just to run this conversion.

2. Convert the PDB image to PAM

Redirect standard output to a new filename. The input argument is optional: when it is absent, pdbimgtopam reads the PDB data from standard input.

$ pdbimgtopam /path/to/palm-image.pdb > palm-image.pam

A successful run normally leaves the terminal quiet and creates the PAM file. The command does not replace the PDB input. A redirection target is different: the shell truncates an existing palm-image.pam before the converter starts, so choose a new name when the old output matters.

For a pipeline or a program that supplies the PDB on standard input, omit the filename:

$ cat /path/to/palm-image.pdb | pdbimgtopam > palm-image.pam

The pipeline form is useful when the PDB is already being read by another command. For a plain file, the direct form is easier to review because it makes the input explicit.

$ pdbimgtopam /path/to/palm-image.pdb > palm-image.pam
$ printf '%s\n' "$?"
0

3. Verify the PAM header before opening it

PAM is a binary-capable Netpbm format. Its header is readable text, but the pixel data that follows it is not. Inspect only the first lines and use a format-aware tool for the rest.

$ sed -n '1,7p' palm-image.pam
P7
WIDTH 160
HEIGHT 160
DEPTH 1
MAXVAL 1
TUPLTYPE BLACKANDWHITE
ENDHDR

Your dimensions will depend on the Palm image. The useful checks are the P7 magic value, a plausible width and height, DEPTH 1, and an ENDHDR line. The installed command emits grayscale PAM output. For a monochrome Pilot image, the documented maximum value is 1. The manual also documents maxval 255 for a non-monochrome input, while noting that Pilot images are always monochrome.

Use file as a second, non-destructive check:

$ file palm-image.pam
palm-image.pam: Netpbm image data, size 160 x 160, 1-bit grayscale, rawbits

The exact wording can vary with the file database installed on your system. It should identify a Netpbm image and report dimensions that agree with the PAM header. A zero-byte or unexpectedly small file is a failed conversion, even if a shell pipeline hid the converter's exit status.

4. Preserve an image note when one exists

PDB Image records can carry a note. Without an option, pdbimgtopam ignores it. Pass -notefile= with a separate destination to save the note:

$ pdbimgtopam \
    -notefile=/path/to/palm-image.note \
    /path/to/palm-image.pdb > palm-image.pam

The option name includes an equals sign, followed by the note filename. The image still goes to standard output; the note goes to the file named by -notefile. If the PDB has no image note, do not assume that a note file proves the image conversion succeeded. Check the PAM output and exit status as well.

Keep the note separate from the PAM file. It is metadata extracted from the PDB, not part of the PAM image stream, so concatenating the two files would make neither one a reliable standalone result.

5. Avoid losing an existing conversion

Shell redirection is not transactional. To keep an earlier PAM file while testing a new conversion, write to a temporary name in the same directory and replace the old file only after verification:

$ pdbimgtopam /path/to/palm-image.pdb > palm-image.pam.new
$ test -s palm-image.pam.new
$ sed -n '1,7p' palm-image.pam.new
$ mv -- palm-image.pam.new palm-image.pam

The mv command changes the directory entry, so run it only when the new header and dimensions are correct. If conversion or verification fails, leave the original file alone and remove the incomplete palm-image.pam.new after checking that it is the disposable file. Do not use a wildcard with rm for cleanup.

If you need to recover after an accidental overwrite, restore the destination from your backup or filesystem snapshot. pdbimgtopam cannot reconstruct an older PAM file that was already truncated, although the original PDB remains unchanged and can be converted again.

6. Diagnose the common failures

An input-open error usually means the path is wrong or the file is not readable. Inspect it without changing anything:

$ ls -l -- /path/to/palm-image.pdb
$ test -r /path/to/palm-image.pdb && printf '%s\n' 'input is readable'

If the command reports malformed PDB data, check that the file is a Palm Pilot Image Viewer PDB containing an Image record. A generic Palm database is not automatically a supported input. Keep a copy of the original while investigating.

If the terminal fills with diagnostic details, rerun without -verbose. That option is for inspecting the PDB Image header and processing information. It does not make the converter more compatible. Use it when you need to see the stored title, dimensions, pixel packing or other input details:

$ pdbimgtopam -verbose /path/to/palm-image.pdb > palm-image.pam
pdbimgtopam: PDB IMAGE header:
pdbimgtopam:   Width: 160
pdbimgtopam:   Height: 160

The exact verbose fields depend on the PDB. Standard error carries these messages, so the PAM data remains on standard output when you redirect it as shown. Do not redirect both streams into the PAM file.