undefined | Better HN

0 pointshanche5y ago0 comments

I have seen pdf files swell to ~ ten times the original size when I edit them with Preview. Apparently, Preview will reencode images upon saving, often choosing a less efficient encoding than original. The most extreme cases I encountered would be files scanned in black and white, with Fax or JBIG2 encoding. Since I use such files a lot, I use pdfpen instead for all my pdf editing tasks.

0 comments

3 comments · 1 top-level

crazygringo5y ago· 2 in thread

I've only ever seen that happen when re-exporting using Quartz filters, where the whole point is to re-encode, and saving an e.g. 300-page PDF will take several minutes, with a progress bar.

If you're just using Preview to rearrange/combine/etc. pages, no re-encoding happens and file size stays the same.

Believe me, I do a lot of PDF management in Preview. Even to the point of creating my own Quartz filters in the ColorSync Utility precisely so that I can intentionally re-encode images when I want to. (Because the Apple-provided Quartz filters are hard-coded to abusrdly high or absurdly low resoltions.)

hancheOP5y ago

It’s been years since I stopped using Preview for PDF files, generally using Skim for reading and pdfpen for editing them. Perhaps something changed since then? That is good news, if so.

hancheOP5y ago

I should have tried it before replying, but did not have easy access to my laptop. Now I redid the experiment. Starting with a 24 page scanned pdf, I deleted the first page using Preview, then saved and closed the file. It swelled from 2 MB to 6.7 MB. Looking into the file, I see that all the images in the original are encoded with CCITTFaxDecode, while the images in the edited file are encoded using FlateDecode. I cannot see anything relevant to the issue in the preferences.

j / k navigate · click thread line to collapse