Posted by
David Faught on
Sep 15, 2006; 5:36pm
URL: https://forum.world.st/TPainter-inflation-routines-tp129412p129414.html
On 9/15/06, Andreas Raab <
[hidden email]> wrote:
> David Faught wrote:
> > 1. To better see what was going on in the Form>>#traceOutlines
> > method, I inserted a few lines like "outer asMorph openInWorld." The
> > morphs that came out were on the order of 2 to 3 times bigger on the
> > screen than the original appeared in the viewport. Why is that?
>
> To avoid 1 pixel shapes which are problematic.
This must be a problem for the later Subdivision process. I would
guess that a 1 point polygon should work okay for the image->polygon
extraction.
> > 2. In the Form>>#traceOutline:do: method, in order to find a starting
> > point for edge tracing, there is a line that finds the smallest
> > enclosing rectangle for a form followed by a search of the first
> > returned line of that rectangle for the first non-background pixel.
> > There is some extra work being done here somewhere because the
> > smallest enclosing rectangle does not appear to be used anywhere else,
> > and all that really needs to be searched for is the first upper left
> > non-background pixel. The bottom right of the smallest enclosing
> > rectangle is of no concern here, right? Am I missing something here?
>
> Your observation is correct. There is no particular need for the right
> and bottom border. You could probably do even random sampling to find a
> starting point.
I think that a random sample to find an edge point might be a little
extreme. However, it also appears to me that later on in the
Form>>#traceOutline:do: method in the actual edge tracking loop, it
might be beneficial to try to find only corners of polygons to reduce
the point count somewhat. If the search direction is the same as when
the last point was found, then they are in a straight line and this
point only needs to be output if the next point is in a different
direction. I guess that logic is a little more complex than I
originally thought as the last, current, and next points all need to
be considered. The extra logic per point might outweigh the savings
in point count.
Thank you for your input.