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[mkgmap-dev] help needed for graphical problem

From GerdP gpetermann_muenchen at hotmail.com on Thu Feb 12 21:15:23 GMT 2015

Hi Andrzej,

I took the one below "Kompakte Variante" from the german wiki
http://de.wikipedia.org/wiki/Bresenham-Algorithmus

Maybe I miss something, but I don't see how I could calculate a 
grid point on the line as I think that's the initial problem that I
try to solve with the loop. 

I guess I should get my result
by calculating the intersections of the given
line with a few horizontal and vertical lines going through
the grid points next to the calculated point on the line (using float
arithmetic)

Not sure if the code for that is simpler...

Gerd


popej wrote
> Hi Gerd,
> 
>  > Or do you see a simple way to limit the
>  > iteration to a part of the way near the wanted point?
> 
> I have looked at algorithm here:
> http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm
> 
> It looks simple, it calculates error to grid at each step by adding a 
> value representing ascent (or descent) of a line. If error is bigger 
> than 0.5 grid, then coordinate is increased and error recalculated 
> against new coordinate. State of algorithm is defined by 3 values: grid 
> coordinates and error. I think there shouldn't be a problem, to restore 
> these 3 variables for any point (grid point) of a line and then make 
> next 10 iterations.
> 
> -- 
> Best regards,
> Andrzej
> _______________________________________________
> mkgmap-dev mailing list

> mkgmap-dev at .org

> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev





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