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Xiaolin Wu's line algorithm: Difference between revisions
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{{task|Raster graphics operations}}[[Category:Graphics algorithms]]
Implement the [[wp:Xiaolin Wu's line algorithm|Xiaolin Wu's line algorithm]] as described in Wikipedia. This algorithm draw antialiased lines. See [[Bresenham's line algorithm]] for ''aliased'' lines.
=={{header|BBC BASIC}}==
{{works with|BBC BASIC for Windows}}
<lang bbcbasic> PROCdrawAntiAliasedLine(100, 100, 600, 400, 0, 0, 0)
END
DEF PROCdrawAntiAliasedLine(x1, y1, x2, y2, r%, g%, b%)
LOCAL dx, dy, xend, yend, grad, yf, xgap, ix1%, iy1%, ix2%, iy2%, x%
dx = x2 - x1
dy = y2 - y1
IF ABS(dx) < ABS(dy) THEN
SWAP x1, y1
SWAP x2, y2
SWAP dx, dy
ENDIF
IF x2 < x1 THEN
SWAP x1, x2
SWAP y1, y2
ENDIF
grad = dy / dx
xend = INT(x1 + 0.5)
yend = y1 + grad * (xend - x1)
xgap = xend + 0.5 - x1
ix1% = xend
iy1% = INT(yend)
PROCplot(ix1%, iy1%, r%, b%, g%, (INT(yend) + 1 - yend) * xgap)
PROCplot(ix1%, iy1% + 1, r%, b%, g%, (yend - INT(yend)) * xgap)
yf = yend + grad
xend = INT(x2 + 0.5)
yend = y2 + grad * (xend - x2)
xgap = x2 + 0.5 - xend
ix2% = xend
iy2% = INT(yend)
PROCplot(ix2%, iy2%, r%, b%, g%, (INT(yend) + 1 - yend) * xgap)
PROCplot(ix2%, iy2% + 1, r%, b%, g%, (yend - INT(yend)) * xgap)
FOR x% = ix1% + 1 TO ix2% - 1
PROCplot(x%, INT(yf), r%, b%, g%, INT(yf) + 1 - yf)
PROCplot(x%, INT(yf) + 1, r%, b%, g%, yf - INT(yf))
yf += grad
NEXT
ENDPROC
DEF PROCplot(X%, Y%, R%, G%, B%, a)
LOCAL C%
C% = TINT(X%*2,Y%*2)
COLOUR 1, R%*a + (C% AND 255)*(1-a), \
\ G%*a + (C% >> 8 AND 255)*(1-a), \
\ B%*a + (C% >> 16 AND 255)*(1-a)
GCOL 1
LINE X%*2, Y%*2, X%*2, Y%*2
ENDPROC</lang>
=={{header|C}}==
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#undef round_
#undef rfpart_</lang>
=={{header|Go}}==
<lang go>package raster
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