Ghostscript 10.6 has a bug that truncates JPEG data by 1-15 bytes.
This adds detection and repair by comparing output images to input
images and restoring the original bytes when truncation is detected.
- Add warning when GS 10.6+ is used with PDF/A output
- Add _repair_gs106_jpeg_corruption() to fix damaged JPEGs after
Ghostscript processing
- Add unit tests for the repair function
For at least the PDF associated with this issue, disabling subset
fonts prevents Ghostscript from mangling the encoding when it is usable but not well-formed.
Fixes#1592
Instead the standard executor will fall back to threads.
semfree caused test failures with Py3.14:
https://github.com/ocrmypdf/OCRmyPDF/issues/1558
In retrospect and with emerging Python tech like freethreading, semfree is becoming less necessary. We can use threads for the time being.
A consequence is that performance may be lower on Lambda and Termux when we are using threads and not shelling out work.
strip_invisible_text resets the text render mode on each `BT` (begin text) command. However the text state is not actually reset for each text element, only for each page.
The pdf reference says:
> The text state operators can appear outside text objects, and the values they set
> are retained across text objects in a single content stream. Like other graphics
> state parameters, these parameters are initialized to their default values at the
> beginning of each page.
>
> -- https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/pdfreference1.7old.pdf#page=397
With the current implementation, a text object is only deleted if it contains a `3 Tr` command (setting the text rendering mode to invalid). However the rendering mode may be set once and then not changed for multiple text objects or set outside of a text object.
In that case only the first text object (which contains the `3 Tr`-command) is removed. This not only leaves the other text objects in the pdf, but also makes them visible, since the text object that contained the `3 Tr`-command is removed.
This PR updates `strip_invisible_text` to not reset the rendering mode for each object and to keep track of the rendering mode when the graphic state is pushed/popped.
Apparently, Ghostscript simply uses temporary files when asked to write to stdout. We're already using temporary files internally, so this eliminates some redundant copies.
James R. Barlow
5HT2
Alina BürgeandGitHub
BBC-EsqandGitHub
Odin DahlströmandJames R. Barlow
jbarlowandGitHub
Quentin FuxaandGitHub
Kara Engelhardt
Ali MJ Al-Nasrawy