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strokeBounds
wrong when applyMatrix=false
#2065
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For round joins, i similarly believe that the current ellipse based approach won't work consistently when
I am fairly certain that should do the trick but I have not tested it yet and there might be a simpler way. |
I tested the approach from my previous comment and while its a better approximation, it does not work all the time. Two more ideas: create a bezier curve approximation of the round join arc in local space. Apply the matrix to the bezier positions/handles and compute the bounds of the curve to merge with the overall bounds (and of course do this for every joint). Or: Do it the most simple way of simply sampling the arc of the round join in multiple positions. Multiply all sampled positions by the matrix and min max them respectively. The first approach might be a bit more expensive but should nicely work with all the existing code in paper as we only need to create a temporary curve for each join. The second approach is dead simple and relatively cheap but its hard to pick a sample count that works well with all kinds of different scaling factors/matrices. |
I just tested the first approach from my previous comment, essentially estimating the round join arc with curves and that appears to work consistently. To summarize for round joins:
|
strokeBounds
are often wrong in a bunch of basic configurations whenapplyMatrix
is set tofalse
. This mainly appears to affectround
andmiter
bounds, but I was also able to create wrong results withbevel
.Link to reproduction test-case
link
After years of not having looked at the paper source code, I am pretty convinced, that the current implementation of
getStrokeBounds
can't work in a lot of cases whenapplyMatrix
is set to false because of the waymatrix
andstrokeMatrix
are separated. i.e for the bevel and miter case, you really want to calculate the stroke geometry in local space and simply apply the paths matrix last to get consistently correct results that match the canvas stroke geometry.Hope I didn't miss anything :)
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