|Re: Overlay Cutting Machine !|
Message #27 Posted by spb on 22 Apr 2011, 7:41 p.m.,
in response to message #26 by svisvanatha
Yes, this is one of the main reasons the overlay generator produces output in the form of an SVG.
If you look at a rasterised image format (like for example JPG or GIF) it consists of a list of pixels and their values. So if you could read the binary blob of a JPG directly, it would look something like: draw a dot of such-and-such colour, then draw a dot of such-and-such colour, then draw a dot of such-and-such colour, and so on for however many pixels there are in the image. This is a bit of a simplification, but that's the basic idea.
If you look at the SVG output created by the overlay generator, you can see it is a text file (specifically an XML document). It contains instructions like `make a rectangle so wide and so high'.
In something like a CNC machine or laser cutter the statements in the SVG can be directly translated into instructions to the device: `make a rectangle so wide and so high' becomes, directly, `make a rectangular cut so wide and so high'. And so on.
SVG also has the advantage of being scalable without loss. This is really useful when you're trying to produce something like a keyboard overlay that has to physically match the dimensions of an existing object. Since different output devices might slightly change the size of the overlay (although they shouldn't because everything is given in dimensions of mm) this is very useful if you have to tweak the size of the overlay---changing the size won't result in any blurriness or other scaling artefacts.
If you are planning on outputting an overlay to a cutter of some sort, you'll need to use two passes. One to output the labels and so forth to the sheet to be cut, and then another to do the cutting. Most cutter frontends should allow you to select which objects/paths to cut and which to ignore. Alternately you can just manually create a second SVG that contains only the cut lines (the key outlines and the outline of the overlay itself).
If this is something a lot of people plan on doing I could easily modify the generator to create both a `cut' and a `label' SVG file.