Added new SVG Branch which is much faster and compares SVGs directly rather than doing renderings in ImageMagick. Still needing some work but illustrates proof of concept.
Scripts for performing image diffs between pcbnew layout revisions. Extended to show the graphical diff in a webpage. Also included some general Kicad/Fossil observations.
The workflow describes how to use a git repository for Kicad printed circuit board board versions. Kicad uses text files for schematic and pcb layout files. Whilst it is easy enough to generate and diff two pcb layout files, the results are almost meaningless as it is impossible to decide what items have moved where.
Additionally, Spuders workflow relied on git - and I rather prefer Fossil-scm as it is a more complete solution (has a wiki and bugtracker built in) and is a small memory footprint.
Also, Spuder's workflow relied on a python script that was downloaded to a /tmp directory. This makes the solution problematic if you are without internet access.
The code is pretty sloppy and fairly sparsely commented but functional. The diff program should be run within a fossil checkout and takes 0, 1 or 2 commit hashes as arguments. With 0 arguments, the script compares the working copy with the last committed version (i.e what has changes since the last commit). With 1 argument, the current checkout is compared to the version identified and with two commit hashes a diff between those versions is calculated.
The diffed versions of the pcb are then used to generate parallel sets of svg files using the kicad python interface. The svg files are then converted to png and cropped to just the board area. ImageMagick is used to manipulate the images to highlight the changed items.
Finally the images are presented in a webpage - clicking an image will bring up a 3-pane diff showing before and after and the composite image with the differences highlighted. The webpage generation code needs abstracting (next part of project). The three pane view is accompanied by a text diff (however, this is very limited and for it to be meaningful really needs a tool to 'reverse parse' the diff and generate a tree structure - i.e a change is noted in a gr-text line but this line is in the s-expression definition of a module that has been moved. Once the diff has been noted, you need to go back up through the s-expression tree to determine the originating module/net etc.
Determining coordinate position is also tricky. It is straightforward to overlay a grid but trickier to compute the necessary offset and scales - this is possible with the python interface but this seems to be in evolution at present. Adjusting or placing an auxillary zero causes problems. Plan to generate a full sized svg image of each page, do the visual diff and then crop the diff to the image extents. Then go back and apply the same crop to the DIFF_1 & DIFF_2 images & at the same time calculate the scale factor and the grid co-ordinates.
Working on python parsing of .kicad_pcb file to extract module/track location info. I have doubled the size of the svg to improve the render detailing when converted to png. Would like to be able to do all of thisi in the svg format.
Kicad tends to modify some of the minor data in the checkout making commits a bit 'noisy'. I have adopted the scheme proposed here https://jnavila.github.io/plotkicadsch/ to amend the kicad files before committing them. Although there is quite extensive scripting support in fossil it seems quite difficult to replicate the clean and smudge technique reliably in Fossil. There is a wrapper project called fsl (http://fossil.0branch.com/fsl/home) which acts as an interceptor to fossil commands and, additionally offers some extra shortcuts and some more colourful logging options (and the Dresden branch allows the use of simple revision numbers). The behaviour is controlled by a ~/.fslrc file which I have included in this repo.
