Trace image?

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Trace image?

Postby supernugget » Fri Mar 16, 2012 4:42 pm

Hi,

I've imported a .png and I am wondering if there is a way to automatically trace the edge of the image.
To clarify, this is a letter logo and I need to find the total distance around the edges (inside and out) of all the letters.

Thanks in advance
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Postby supernugget » Fri Mar 16, 2012 4:50 pm

Update:
I used photoshop to generate a stroked image, which gets the edge I need, but it still is a single image and is unmeasurable........any help?
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Postby Clive » Fri Mar 16, 2012 5:17 pm

supernugget wrote:Update:
I used photoshop to generate a stroked image, which gets the edge I need, but it still is a single image and is unmeasurable........any help?


Hi supernugget

Not sure about Community version but in Version 3 pro there is a 'measure tool' which will give you the total length of a selection.
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Postby supernugget » Fri Mar 16, 2012 6:58 pm

I appreciate the response.
I am familiar with the function, but I need to convert the .png into a .dxf so that I can get the measurements; or some equivalent process; the measurements being the goal.

Thanks again

also, I'm on a mac mini / QCAD 2.2.3.0
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Postby Clive » Fri Mar 16, 2012 7:37 pm

supernugget wrote:I appreciate the response.
I am familiar with the function, but I need to convert the .png into a .dxf so that I can get the measurements; or some equivalent process; the measurements being the goal.

Thanks again

also, I'm on a mac mini / QCAD 2.2.3.0


It might be worth trying Inkscape, I think I read somewhere that its possible to export a png. file to a dxf file!
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Postby hungerburg » Sat Mar 17, 2012 3:04 pm

PNG is not designed to represent real world objects in any other sense, than what they look like. It is not designed to perform measurements of such objects.

PNG is a bitmap graphics format. A bitmap is a matrix of X by Y pixels. A pixel is not a physical unit.

There is one anchor into the physical world: Pixels can be correlated with the DPI value. Eg at 300 DPI, 600 pixels correspond to two inches. Eg at 10 DPI, 600 pixels correspond to 60 inches.

So you have to place the bitmap into QCAD, then set its width to the width in pixels of the bitmap divided by the DPI value of the bitmap. Voilà, you can use all the QCAD measuring tools on it.

Still, I highly doubt, that your PNG file was created with this use in mind…
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