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Re: Automated test on PDF or SVG output

From: Dan Eble
Subject: Re: Automated test on PDF or SVG output
Date: Mon, 14 Nov 2022 20:39:22 -0500

On Nov 14, 2022, at 04:43, Paolo Prete <> wrote:
> I need to execute the following automated test:
> given a .ly file, I would like to check if the produced output is what I
> expect it to be.

For checking the impact of LilyPond changes on my own scores, I use a
Docker container and a bash script that does this:

1. reads PDF files from two directories recursively
2. converts each page to a bitmap
3. overlays the two versions of each page so that pixels which are white
   in one and black in the other become either red or green
4. collates the new images into new PDF files in a third directory

Then I review every score.

It works well when specific things have moved, appeared, or disappeared.
It can be quite noisy when there have been general changes to spacing.

If that appeals to you, I can send you the scripts privately.

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