2013/6/4 mathog <mathog@...1176...>:
- Compound lines. GDI+ can draw a line with what is essentially a
row of pens of various widths. Define a pen with a narrow stroke, space, wide stroke, space, narrow stroke, and draw a rectangle, and the result is a set of 3 nested rectangles, with a fat central stroke and thinner strokes inside and outside of it. Can SVG do this? I'm thinking one would have to import this in a loop, and create the rectangles one by one with the appropriate "sub" pen.
This can be emulated with vector effects, specifically veStroke. However, Inkscape does not yet implement these. Other possibilities involve using the "Pattern along path" LPE, or a hairy hack involving stroke markers (e.g. add many nodes to the base path and a thin mid marker that corresponds to the stroke structure).
- Clipping regions can be combined with XOR, UNION, INTERSECT and so
forth. However, I do not recall in the present EMF output that clipping information is passed into the driver. Rather I vaguely recall that it was applied many levels above and the clipped shape is what is sent to the output driver. Other than for clipping there does not seem to be a way to create compound regions using these operators. I don't think SVG has these operators for general shapes either. Inkscape performs these operations on paths, but just puts the combined path in the SVG.
Using a group of paths together with the clip-rule property can partially emulate XOR and UNION. INTERSECT is equivalent to defining a clipping path for a clipping path. This might be more robustly representable as boolean vector effects (veIntersect, veUnion, veExclude) from SVG 2.0 (or is it SVG 1.2?).
- Gradient curves. GDI+ does this by specifying an array of points
(the curve) and a corresponding array of colors, and then some rules about how to interpolate colors. (Fill is another story, that uses a brush with a defined gradient.) I could not find an example of SVG stroking a gradient curve like this, other than by breaking it down into a series of separate line segments of slowly varying color.
Not sure if this exists with SVG, probably needs to be lowered to mesh gradients.
Regards, Krzysztof