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Alpha fill check action list

Posted: Wed Jun 04, 2025 12:52 pm
by JavierLFPC
Hi,

I need to create an action list in PitStop pro that detects any object with an alpha fill and show me an error message if there is not an alpha fill.
Typically the jobs will include jpeg objets with transparency.
In attachment you can find 2 pdf files, with and without transparency.
NoTransparency.jpeg
NoTransparency.jpeg (137.01 KiB) Viewed 5585 times
Transparency.jpeg
Transparency.jpeg (217.05 KiB) Viewed 5585 times

Re: Alpha fill check action list

Posted: Fri Jun 06, 2025 2:08 pm
by freddyp
The JPEG format does not support transparency, so a method that is based on the properties of the image will not work. What you are referring to is undoubtedly the fact that there are white pixels.

Here is a conceptual way of detecting those. Run a PitStop Server Action List on the image (make sure to enable image input on the app):
Trace path (you can play a bit with the resolution and the white threshold; white holes can be ignored)
Select last added objects
Log selection

If the size of the created trace path is smaller than that of the image, there were "transparent" pixels. All other jobs do not have them.