PDF to JPEG in Preview App Big Sur 75 inches bug

Only the macOS Product team can fix internal Preview build issues, and there is no user fix for it ignoring DPI in image exports from PDF. That product team does not participate here, so if you want them to know there is an export issue, send them detailed feedback.

At this time, continue to use the Automator solution you have been using, or my Terminal solution if you want.

It does seem to be a bug in Preview.

As a workaround, I found that the corresponding action in Automator does NOT suffer from this bug, so I was able to create a quick Automator application to convert pdf to jpeg with a given resolution.

Save it anywhere you like, and drag and drop files to convert. I checked the box "Show this action when the workflow runs", so you can even change the resolution and file type every time you run it.

This saves the created file on the Desktop, but you can choose a different location, of course. It also rewrites without warning; you may want to turn that off, for safety.

You mean 75dpi?

I will have to check in a few minutes when I get back to my mac but I’m pretty sure I could use higher values. The options available may depend on the file you have. Maybe you have a pdf file that was itself obtained from a low resolution jpeg? Did you try with a pdf known to contain vector data?

Oh wait... I see. While I can choose any resolution I want, it does NOT get reflected in the created file.

In fact, resolution is not the big deal, the problem is that the picture dimensions are not set appropriately.

There is always the Terminal to do the PDF to JPG conversion right, where y is the value returned for pixelHeight in the sips -g all command. The formatOptions value is the JPG quality.

man sips
sips -g all foo.pdf
sips -Z y -s dpiHeight 300.0 -s dpiWidth 300.0 -s format jpeg -s formatOptions 100 -o foo.jpg foo.pdf

The resulting foo.jpg will have the same dimensions as the PDF and will be confirmed by the Preview Inspector to be 300 DPI.

Automator also has a PDF to image action where you can set the DPI and the output image type. Makes a nice drag and drop PDF to image solution.

That is not what I'm seeing here. I wrote 300, but I could have written 600, or whatnot.