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#How to see dpi of pdf pdf#

Thanks Harlequin for pdfimages and Spiffeah for the alert about multiple images per page (it's rare, but I've found some). I'm using it in live fire and it works great.

To get resolution, compute areas of bounding box in inches squared, divide dots squared by inches squared, take the square root, and round to the nearest multiple of 10.įull answer with script is below.

Add the total areas of the images to get the number of dots squared.

This time identify will give number of pixels.

Extract images from the first page using pdfimages.

#How to see dpi of pdf pdf#

Extract the bounding box from the PDF using identify, taking only the output for the first page, and understanding that the units will be PostScript points, of which there are 72 to an inch.

Thanks to help received, I've posted an answer below: And if in desperate need I could modify the dictionary stack that gs is using long ago, I wrote an interpreter for PostScript Level 1. If I convert the PDF to PostScript I can poke around by hand and find pixel dimensions easily I could probably find image sizes with more work.

They contain one scanned image per page, same resolution each page. My particular documents came out of a scanner.

Since DjVu is a pixel-based format, I want to be sure I use the same resolution in the target DjVu file as was used for the scan.ĭoes anyone know what program I can run, or how I can write a program, to determine what resolution was used to produce a scanned PDF? (Number of pixels might work too as almost all documents are 8.5 by 11 inches.)Ĭlarification after responses: I'm aware of the difficulties highlighted by Breton, and I'm willing to concede that the problem in general is ill-posed, but I'm not asking about general PDF documents. Some documents were scanned at 200dpi, some at 300dpi, and some at 600dpi. I have a large collection of documents scanned into PDF format, and I wish to write a shell script that will convert each document to DjVu format.