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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.

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.

JavierLFPC wrote: ↑Wed Jun 04, 2025 12:52 pm ...In attachment you can find 2 pdf files, ...

Hi JavierLFPC,
I cannot find your PDF files. Only JPG files are shown. Perhaps you could make the PDF files available for download (from a file hoster)?

Hi,

Sure! Here you have a link to download them:
https://www.transferxl.com/es/download/08vH2W4mzv5nBc

Thanks!

Hmm, the PDFs only contain simple image data. No alpha fill, no mask and no native transparency.
How is PitStop Pro supposed to find this if the PDF does not even contain the properties to be searched for?

Hello,

I think Freddy's suggestion is the best option so far.

Loic

loicaigon wrote: ↑Tue Jun 17, 2025 2:14 pm Hello,

I think Freddy's suggestion is the best option so far.

Loic

I agree with you

Hey There,

Here is a possible approach based on the folloing postulate: if an image has white pixels, then tracing would result in a smaller object that the page itself. If by contrast, the tracing consists in the full page, then the combination of that trace and the page should result in nothing.
So you can basically detect that nothing or not nothing to report if the page has a pseudo alpha fill (i.e. white pixels).

Take example here:

Source Image:


Tracing Image


Adding a full rectangle


Combining shapes


Remove and report


Loic