kicad-developers team mailing list archive

[Cirilo Bernardo <cirilo_bernardo@xxxxxxxxx>]

>________________________________
> From: Blair Bonnett <blair.bonnett@xxxxxxxxx>
>To: Cirilo Bernardo <cirilo_bernardo@xxxxxxxxx> 
>Cc: Kicad Developers <kicad-developers@xxxxxxxxxxxxxxxxxxx> 
>Sent: Sunday, August 3, 2014 11:24 AM
>Subject: Re: [Kicad-developers] underlay for reconstructing boards
> 
>
>
>On 3 August 2014 12:09, Cirilo Bernardo <cirilo_bernardo@xxxxxxxxx> wrote:
>
>
>
>
>I received a request for a feature some months ago.  The idea is to provide
>>an underlay image to help people duplicate existing board designs, for example
>>when duplicating old circuits to refurbish a device or to recreate the PCB
>>artwork when all you have are old gerber files or perhaps printouts of the
>>gerber images, or cutouts from electronics hobbyist magazines.
>>
>>I believe this can be implemented by:
>>
>>1. adding a checkbox to the bitmap tool to write to an 'Underlay' layer
>>instead of to F.SilkS
>>
>>2. reserving one of the spare layers as 'Underlay'. This layer will be the
>>first rendered and will never be plotted or printed.
>>
>>Any comments/suggestions/objections?
>>
>>- Cirilo
>
>
>I like the idea, but am curious as to how you intend it to be used with multiple layers (e.g., an underlay for both top and bottom copper). Maybe a list of bitmaps assigned to the layer with the ability to toggle between them?
>
>
>Will there be any scaling or offset options when importing the bitmaps, or will the user need to prepare them correctly using an image editor prior to loading them into Kicad?
>
>
>Regards,
>Blair
>


I only intend to have 1 underlay, so if you're reconstructing something like a
6-layer board from gerbers you'll have to load 1 underlay at a time. There will
be minor nuisances at times when a track jumps layers through a via but I don't
believe the complexity of having more than 1 underlay will be beneficial.

The scaling will be controlled by the 'DPI' setting in the bitmap tool. The
bitmap tool creates filled polygons using the image points as the discrete
coordinates. The user may need to use an image manipulation program beforehand
to ensure the best results from an image. For images from a flatbed scanner
I'd use no less than 300DPI (0.08mm per dot).

Offsets can be managed by dragging the resulting inserted module to the
desired position. Remember the underlay is only meant as a guide; even if
the registration with the KiCad grid is not perfect, a human operator will
have no trouble compensating after a little practice.

- Cirilo