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Re: gerber file compare technique


Here's an excellent article by some open-source hardware folks about doing visual diffs on schematics and PCB layouts. They use GEDA for their work but 95% of the information would apply to those of us using KiCad. I'm currently working on a way to automatically render my gerbers into PNG upon commit to git/svn (for easier browsing from smartphones etc) as well as doing a visual diff between each version I check-in.



On 2/16/2012 1:28 AM, Dick Hollenbeck wrote:
Today we transitioned from working prototypes to production orders on a version 2.0 board,
meaning the gerbers have to
be pretty darn close to the known working prototypes, yet you need that last little tweak
to fix the minor issue you found in the low quantity prototype run.

I did not want to do another prototype sized quantity run.  How to reach the confidence
needed to boldly move forward?

One technique I worked up this afternoon involves imagemagick and gerbv and a script.


The above tells how two PNG files can be compared using image XORing.

gerbv can be scripted from the command line to output a *.PNG file for a single layer file
load, both old and new images pertaining to the same layer.

The attached script is just a start, but it can be used to iterate through all your gerber
layers using one old gerber layer and the matching new gerber layer file as matched pairs.

It worked well enough to find a bug in the silkscreen layer for me, and I am quite excited
about its use moving forward, and wanted to share it with all the folks on the developer's
list so that the technique can be refined and expanded upon.

I hope you find the technique useful as a starting point.


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