This tutorial will show you how to create PCB artwork that looks good on display or print and that is intended only as a guide to the reader, not as a source for manufacturing PCB. The result will be a greenish PCB (or any color you want) with silkscreen on top of it. This is probably something you already seen in electronics publications.
There are many ways of doing this. All you need to start are the PDF files plotted by KiCAD and some image editing software (I prefer opensource tools: GIMP or some ImageMagick scripting).
To start, open a finished PCB design in KiCAD and plot some layers. Go to File - Plot and make sure format is set to PDF. You must select a copper layer and a silkscreen. For example, in most situations you will want to plot the bottom copper layer (B.Cu) with the top silkscreen (F.SilkS). If your PCB is SMT build mostly on top copper layer, you will want F.Cu with F.SilkS. On the other hand, if your PCB is built on bottom layer with SMD parts, you will make a mirrored plot of B.Cu and B.SilkS. You should also plot some drill marks. I prefer small marks.
|KiCAD plotting options|
|Import PDF in GIMP|
The first problem is that silkscreen layer is not transparent. Right click this layer and try to Add alpha channel. If it's disabled, then the layer already has an alpha channel.
|Add alpha channel to layer in GIMP|
|GIMP color to alpha|
|Colorize copper layer in GIMP|
All this is also doable using ImageMagick. And here comes the advantage of command line tools: scripting. The steps can be summarized as follows:
- Convert plotted PDFs to PNG (Ghostscript needed);
- Take copper layer PNG and colorize it;
- Take silkscreen layer PNG and make it transparent;
- Overlay the PNGs in the correct order;
- Auto-crop resulted image.
Fot this I made a small shell script that takes the KiCAD project directory as input parameter and generates the PNG file. The script currently has some issues, but if you want to try it you can find it on GitHub.