Rosetta Code

Xiaolin Wu's line algorithm: Difference between revisions

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Xiaolin Wu's line algorithm (view source)

Revision as of 19:09, 7 January 2013

209 bytes added ,  11 years ago
m
→‎{{header|REXX}}: corrected the DO-END comment labels, aligned some statements, added whitespace, simplified ROUND subroutine, added comments. -- ~~~~
(Better D entry)
m (→‎{{header|REXX}}: corrected the DO-END comment labels, aligned some statements, added whitespace, simplified ROUND subroutine, added comments. -- ~~~~)
Line 793:
<br>'''Note''': If at the beginning of the routine abs(''dx'') < abs(''dy'') is true, then all plotting should be done with ''x'' and ''y'' reversed.
<lang rexx>/*REXX program plots/draws a line using the Xiaolin Wu line algorithm.*/
EoE = 1000 /*EOE = End Of Earth, er, plot. */▼
background = 'fa'x /*background char: middle-dot. */
image. = background image. = background /*fill the array with middle-dots*/
plotC = '░▒▓█' plotC = '░▒▓█' /*chars used for plotting points.*/
EoE = 1000 do j=-EoE to +EoE /*drawEOE = End Of gridEarth, fromer... lowest──>highestplot.*/
image.j.0 = '─' do j=-EoE to +EoE /*draw the horizontal axis. grid from lowest──►highest*/
image.j.0.j = '│─' /*draw the " " verical " horizontal axis. */
end image.0.j = '│' /*j " " verical " */
image.0.0='┼' end /*"draw" the axis origin. j*/
image.0.0 = '┼' /*"draw" the axis origin (char). */
parse arg xi yi xf yf . /*allow specifying line-end pts. */
if xi=='' | xi==',' then xi = 1 /*if not specified, use default. */
if yi=='' | yi==',' then yi = 2 /* " " " " " */
if xf=='' | xf==',' then xf = 11 /* " " " " " */
if yf=='' | yf==',' then yf = 12 /* " " " " " */
minX=0; minY=0 /*used as limits for plotting. */
 
maxX=0; maxY=0 /* " " end" " " /*y*/▼
minX=0; maxX=0
call line_draw xi, yi, xf, yf /*call subroutine and draw line. */
minY=0; maxY=0
callborder = 2 line_draw xi, yi, xf, yf /*call subroutineallow andadditional drawspace line.for plot*/
minX=minX-border*2; maxX=maxX+border*2
minXminY=minXminY-border*2; ; maxXmaxY=maxXmaxY+border*2
do y=maxY by -1 to minY; _= say aRow /*build a row*/▼
minY=minY-border ; maxY=maxY+border
do x=minX to maxX
 
_=_ || do image.x.y=maxY by -1 to minY; aRow=
end do /*x=minX to maxX*/
say _ aRow=aRow || image.x.y /*display row*/
end end /*xy*/
▲ say aRow
▲ end /*y*/
exit /*stick a fork in it, we're done.*/
/*────────────────────────────────DRAW_LINE subroutine──────────────────*/
line_draw: procedure expose background image. minX maxX minY maxY plotC
parse arg x1, y1, x2, y2; switchXY=0; dx=x2-x1
▲EoE = 1000 /*EOE = End Of Earth, er, plot. */ dy=y2-y1
dx=x2-x1
dy=y2-y1
if abs(dx)<abs(dy) then do
parse value x1 y1 with y1 x1 /*swap x1 & y1*/
Line 839 ⟶ 836:
 
gradient = dy/dx
xend xend = round(x1) /*────1st endpoint────────────────────*/
yend = y1 + gradient * (xend-x1)
intery intery = yend + gradient▼
xgap xgap = 1 - fpart(x1+.5)
xpx11 = xend
xpx11 = xend; ypx11 = floor(yend); ypx11_=ypx11+1
call plotXY xpx11, ypx11, brite(1-fpart(yend*xgap)),switchXY
call plotXY xpx11, ypx11_, brite( fpart(yend*xgap)),switchXY
▲intery = yend + gradient
 
xend xend = round(x2) /*────2nd endpoint────────────────────*/
yend = y2 + gradient * (xend-x2)
xgap xgap = fpart(x2+.5)
xpx12 = xend; ypx12 = floor(yend); ypx12_=ypx12+1▼
xpx12 = xend
▲ypx12 = floor(yend); ypx12_=ypx12+1
call plotXY xpx12, ypx12, brite(1-fpart(yend*xgap)), switchXY
call plotXY xpx12, ypx12_, brite( fpart(yend*xgap)), switchXY
 
do x=xpx11+1 to xpx12-1 /*────draw the line───────────────────*/
!intery = floor(intery)
!intery_ = !intery+1
call plotXY x, !intery, brite(1-fpart(intery)), switchXY
call plotXY x, !intery_, brite( fpart(intery)), switchXY
intery = intery + gradient
end /*x*/
return
/*────────────────────────────────BRITE subroutine──────────────────────*/
brite: procedure expose background plotC; parse arg p
return substr(background || plotC, 1+round(abs(p)*length(plotC)), 1)
/*────────────────────────────────PLOTXY subroutine─────────────────────*/
plotXY: procedure expose image. minX maxX minY maxY;
parse arg xx, yy, bc, switchYX; if switchYX then parse arg yy, xx
image.xx.yy=bc; minX=min(minX,xx); maxX=max(maxX,xx)
minY=min(minY,yy); maxY=max(maxY,yy)
return
/*────────────────────────────────FLOOR subroutine──────────────────────*/
floor: procedure; parse arg ?; _=trunc(?); return _-(?<0)*(?\=_)
/*────────────────────────────────FPART subroutine──────────────────────*/
fpart: procedure; parse arg ?; return abs(?-trunc(?))
/*────────────────────────────────ROUND subroutine─────────arg2 is place*/
round: procedure; parse arg ?,??; return format(?arg(1), , word(??arg(2) 0, 1))</lang>
'''output''' when using the default input
<pre style="overflow:scroll">
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