Re: [Gimp-user] PCB Editing

[Ofnuts <ofnuts gmx com>]

On 1/17/20 9:32 AM, Sorceress99 wrote:
> I am trying to separate the 2 sides of a printed circuit board photo and can't
> remember how to do it.  The circuit diagram is in blue and the parts layout is
> in black. Wiring placement is in red is irrevelant and can be deleted.  The PCB
> pattern, in blue, is printed on glossy photo paper on a laser printer, in black.
> The print is set on 'high quality' so needs to be sharp and clear. The image is
> then positioned, face down on a blank copper clad PCB then transfered to the
> board by various means such as heat lamination or chemically. Once completed,
> the parts layout is printed on the laser as before, positioned in alignment with
> the circuit side, then transfer to the opposite side of the board as before. Any
> help with separating the 2 images would be appreciated.
>
> Attachments:
> * https://www.gimpusers.com/system/attachments/1338/original/HP-23_PCBFull.jpg

In the monochrome channel mixer

* pushing red to 100% makes the red channel disappear

* You can substract a bit of green from blue or vice-versa to make the
printted circuit grey


Duplicate the resulting layer

Color>Invert on the top layer

Put the top layer in "difference" mode: the grey bits are about the same
in both image, so they becomes 0 (black) while the black and white parts
are changed to their opposite and the difference ins close to 255 (white).

Still some cleaning left to do, and painting where the red tracks have
left white lines in the circuits.

Personally for such a small circuit, I would redraw it, you need a
couple of brushes for the solder points, a brush to draw straight lines,
and wider areas can be filled with the polygon selection.