Latest blog posts
Martin Eve
2024 April 03

Testing times

One of the challenges that we face in Labs and Research at Crossref is that, as we prototype various tools, we need the community to be able to test them. Often, this involves asking for deposit to a different endpoint or changing the way that a platform works to incorporate a prototype. The problem is that our community is hugely varied in its technical capacity and level of ability when it comes to modifying their platform.

...Find out more
Joe Wass
2024 March 18

Mending Chesterton's Fence: Open Source Decision-making

When each line of code is written it is surrounded by a sea of context: who in the community this is for, what problem we’re trying to solve, what technical assumptions we’re making, what we already tried but didn’t work, how much coffee we’ve had today. All of these have an effect on the software we write. By the time the next person looks at that code, some of that context will have evaporated.

...Find out more
Martin Eve
2024 March 15

Credential Checking at Crossref

It turns out that one of the things that is really difficult at Crossref is checking whether a set of Crossref credentials has permission to act on a specific DOI prefix. This is the result of many legacy systems storing various mappings in various different software components, from our Content System through to our CRM. To this end, I wrote a basic application, credcheck, that will allow you to test a Crossref credential against an API.

...Find out more
Patrick Polischuk
2024 March 13

Subject codes, incomplete and unreliable, have got to go

Subject classifications have been available via the REST API for many years but have not been complete or reliable from the start and will soon be deprecated. dfdfd The subject metadata element was born out of a Labs experiment intended to enrich the metadata returned via Crossref Metadata Search with All Subject Journal Classification codes from Scopus. This feature was developed when the REST API was still fairly new, and we now recognize that the initial implementation worked its way into the service prematurely.

...Find out more
  • Menu
search

Warnings, Caveats and Weasel Words

Most of the experiments linked to here are running on R&D equipment in a non-production environment. They may disappear without warning and/or perform erratically. If one of them isn’t working for some reason, come back later and try again.

pdfstamp

 2 minute read.

Overview

Pdfstamp is an open source command-line tool that allows you to add an image or “stamp” to any location on a PDF and to link said image to a URL of your choice.

This means that, when a user opens a “stamped PDF” and clicks on the image, they will (assuming they are connected to the internet) have their browser open and take them to the URL pointed to.

Why?

Well, we needed this functionality for a project that we are developing internally and we thought it might be useful to others in the community.

Syntax

The pdfstamp tool gives you pretty granular control over the positioning and resolution of the placed image. It also allows you to specify how to name files for batch processes.

Usage: pdfstamp [options] |
-d N : Optional. Target DPI. Defaults to 300.
-e EXT : Optional. Extension appended to the PDF filename.
-i FILE : Required. Image file containing image of the stamp.
-l X,Y : Required. Location on page to apply stamp.
-o FILE : Optional. Output directory.
-p P1,P2... : Optional. Page numbers to stamp. -1 is the last page.
-r : Optional. Descend recursively into directories.
-u URL : Optional. Target URL of the stamp.
-v : Optional. Verbose output.

Notes

Pdfstamp is non-destructive. It will always generate a new PDF with the stamp added to it. However, If you are using pdfstamp on a “linearized” (aka “optimised” or “fast web view enabled”) PDF, the resulting PDF will need to be re-linearized using ghostscript’s pdfwrite device, and specifying -dFastWebView or any similar tool (e.g. Acrobat Pro).

Pdfstamp is designed for batch-processing and, to give you an idea of performance, we were able to stamp, link and re-linearize (using pdfopt) 500 journal article PDFs in about eight seconds on a recent-vintage Macbook Pro. Performance very much depends on the resolution and size of the image that you are adding to the PDF and the size of the PDF itself.

What next?

If you have any comments, suggestions, bug reports or (hint, hint) patches, please fee free to send them to us here at:

labs_email

Or just complain bitterly on Twitter.

Page owner: Crossref   |   Last updated 2013-January-22