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 Post subject: How to import bitmap graphics without scaling?
PostPosted: 01 Aug 2017, 02:52 
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Joined: 06 Mar 2017, 23:13
Posts: 17
Is it possible to import pre-designed silkscreen graphics (PNG, TIF, etc) without rescaling them?

The size of imported graphics is always somewhat skewed because the rectangle that you have to draw before importing the graphic will never match the shape of the image exactly.

The only way that I can see to get the proportions correct is to enter the corner coordinates manually in the Shape Properties window.

Since bitmap graphics inherently include a DPI parameter, why not import the graphic at the original resolution and dimensions instead of requiring the bounding box rectangle to be drawn first?

This would prevent unwanted skewing of company logos, etc.


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 Post subject: Re: How to import bitmap graphics without scaling?
PostPosted: 02 Aug 2017, 09:27 
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Joined: 09 Jun 2010, 08:12
Posts: 208
Unfortunately, it is unreal, to extract something helpful from graphics formats. In this situation, the only way is check dimensions manually.


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 Post subject: Re: How to import bitmap graphics without scaling?
PostPosted: 02 Aug 2017, 09:52 
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Joined: 20 Jun 2015, 14:39
Posts: 939
Here are two possible work-arounds...

1) Save the silkscreen graphic as a Gerber file. Now any time you need it just import its Gerber file (Import Mode: Add, Convert to: Top Silk) into your layout, select all of its objects, move them using the arrow keys to the desired location and resave your PCB.

2) If the silkscreen graphic has a ton of objects, moving it around the PCB could be a slow process. This second work-around would speed up a slow placement process by grouping all of the silkscreen graphic's objects into a component (select all of its objects, right-click on one of the selected objects and choose Group into Component in the pop-up menu) and saving it into one of your User Patterns libraries (right-click on the new "component" and select Save to Library in the pop-up menu). Now any time you need it just place the new "pattern" into your layout at the desired location (e.g. drag it with your mouse or enter the desired coordinates), right-click on it, select Ungroup Component in the pop-up menu and resave your PCB.

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Tom


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 Post subject: Re: How to import bitmap graphics without scaling?
PostPosted: 03 Aug 2017, 01:42 
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Joined: 06 Mar 2017, 23:13
Posts: 17
Thanks Serg, that's too bad. Seems like most apps can read the DPI and pixel dimensions, then calculate the absolute physical size as a function of DPI x width and DPI x height. At least the Diptrace method is still better than Eagle, which uses a horrible bitmap conversion script that takes forever to run on a high-resolution image.

And thanks Tomg for the ideas. In the first case it's still necessary to enter the dimensions manually, which is the main problem. But I never thought about importing a Gerber file to use as a silkscreen, that could have some interesting possibilities. Perhaps I can find a way to export a Gerber file from Inkscape at 1:1 scale and work around the scaling issue.


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