PDF to JPEG Conversion in Omnis Studio using Process Worker

A useful discovery from the Omnis community---demonstrating how to convert a PDF into a JPEG image file using macOS or Windows command-line tools, and integrating it with Omnis Studio via a Process Worker.

macOS — Using sips

The built‑in sips command in macOS can convert a single‑page PDF to a JPEG image with good resolution.

sips -s format jpeg input.pdf --out output.jpg

You can adjust size with optional parameters like pixelWidth and pixelHeight if you want to constrain the output (e.g., 80×80).
For many uses---such as Kelly’s ImageBox external or a PICT field in a complex grid---you may simply display the full image at a constrained size, keeping the original resolution intact.

To automate it within Omnis Studio, use a Process Worker:

Calculate command as "sips -s format jpeg /path/to/input.pdf --out /path/to/output.jpg"
Do processWorker.$init(command)
Do processWorker.$run()
Do processWorker.$readlines(kOProcessStdout) Returns list
Calculate PictFile as list.1.stdout

This runs the command and captures the output filename from the process results.

macOS — Handling Binary Output (Advanced)

The sips command does not output binary image data to STDOUT, which means a Process Worker cannot capture raw image bytes directly.
To work around this limitation, you can convert the output image to Base64, which is safe to return via STDOUT in Omnis.

Example command:

sips -s format png input.icns -o __temp_sips_output.png && base64 __temp_sips_output.png && rm __temp_sips_output.png

What the steps do

• Converts the input file to PNG and saves it as a temporary file.\
• Encodes the temporary file as Base64 (safe for Process Worker).\
• Deletes the temporary file afterward.

This allows Omnis to receive the image data entirely through STDOUT as text, which you can decode back to binary inside Omnis if needed.

Notes

• Replace file names and formats (png, jpeg, etc.) as required.\
• If your receiving process can accept binary input, you could replace base64 with cat, but Process Worker cannot safely capture raw binary.\
• Temporary files are fine for normal usage but may be slower for large images or batch processing.

Windows — Using ImageMagick

On Windows, use ImageMagick, which supports PDF-to-JPEG conversion:

magick input.pdf output.jpg

Integrate via Process Worker exactly as on macOS by adjusting the command string.

Contributors

• Doug Easterbrook — Arts Management Systems\
• Mike Matthews — Lineal Software Solutions

Very cool 👍