Pixel-vector optimising for lisp-font?

[HPW]

I am thinking about a converter from bitmaps fonts to a lisp-format describing the needed Pixelgrid

Example letter bitmap 7 x 15 (zoomed):


I scan the bitmap vertical and horzontal and get 2 vector lists.

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Bitmap: 7 x 15 Pixel

Vertical scan:

;     X1 Y1 X2 Y2       Length
(list  0 10  0 11)      ;2
(list  1  7  1  9)      ;3
(list  2  1  2  1)      ;1
(list  2  4  2  6)      ;3
(list  2  8  2  8)      ;1
(list  3  3  3  3)      ;1
(list  3  8  3  8)      ;1
(list  4  1  4  1)      ;1
(list  4  4  4  6)      ;3
(list  4  8  4  8)      ;1
(list  5  7  5  9)      ;3
(list  6 10  6 11)      ;2


Horizontal scan:

;     X1 Y1 X2 Y2       Length
(list  2  1  2  1)      ;1
(list  4  1  4  1)      ;1
(list  3  3  3  3)      ;1
(list  2  4  2  4)      ;1
(list  4  4  4  4)      ;1
(list  2  5  2  5)      ;1
(list  4  5  4  5)      ;1
(list  2  6  2  6)      ;1
(list  4  6  4  6)      ;1
(list  1  7  1  7)      ;1
(list  5  7  5  7)      ;1
(list  1  8  5  8)      ;5
(list  1  9  1  9)      ;1
(list  5  9  5  9)      ;1
(list  0 10  0 10)      ;1
(list  6 10  6 10)      ;1
(list  0 11  0 11)      ;1
(list  6 11  6 11)      ;1

So I want to draw the pixels with the vectors with the largest length and want to avoid double vectors.

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Wanted Result:

(list  0 10  0 11)      ;2
(list  1  7  1  9)      ;3
(list  2  1  2  1)      ;1
(list  2  4  2  6)      ;3
(list  3  3  3  3)      ;1
(list  4  1  4  1)      ;1
(list  4  4  4  6)      ;3
(list  5  7  5  9)      ;3
(list  6 10  6 11)      ;2
(list  1  8  5  8)      ;5

Any lispish ideas?

[HPW]

After thinking about it my first idea is:

I build a list with all vectors and sort it after the vector lenght.
Then I start with the longest vectors and build a second list
with the setted single pixels. Every new vector is checked if it will set any new pixel.
If not it will be dropped from the result-vector list.

I will try this out.

[cormullion]

How about a list of coordinate pairs:

'((0 10) (0 11))

I can see this being useful sometimes...

[HPW]

My current implementation of the optimising part:
(The sublists in resultlist have now an additional value for the vector direction)

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 (setq	pixellist '()
	resultlist2 '()
 )
 (dolist (vlst resultlist)
	(setq	vectordir(nth 1 vlst)
		vectorstart(nth 0(nth 2 vlst))
		vectorend(nth 1(nth 2 vlst))
	)
	(if (= vectordir 0)		;X
	 (begin
	  ;Check if vector is needed
	  (setq VectorIsNeeded nil)
	  (for (x(first vectorstart)(first vectorend)1)
		(if (not(member (list x (last vectorstart)) pixellist))
			(setq VectorIsNeeded true)
		)
	  )
	  (if VectorIsNeeded
	   (begin
	   (setq resultlist2 (append resultlist2 (list vlst)))
	   ;Add all pixel to pixellist
	   (for (x(first vectorstart)(first vectorend)1)
		(if (not(member (list x (last vectorstart)) pixellist))
			(setq pixellist (append pixellist (list (list x (last vectorstart)))))
		)
	   )
	   )
	  )
	 )
	)
	(if (= vectordir 1)		;Y
	 (begin
	  ;Check if vector is needed
	  (setq VectorIsNeeded nil)
	  (for (y(last vectorstart)(last vectorend)1)
		(if (not(member (list (first vectorstart) y) pixellist))
			(setq VectorIsNeeded true)
		)
	  )
	  (if VectorIsNeeded
	   (begin
	   (setq resultlist2 (append resultlist2 (list vlst)))
	   ;Add all pixel to pixellist
	   (for (y(last vectorstart)(last vectorend)1)
		(if (not(member (list (first vectorstart) y) pixellist))
			(setq pixellist (append pixellist (list (list (first vectorstart) y))))
		)
	   )
	   )
	  )
	 )
	)
 )