Xiaolin Wu's line algorithm: Difference between revisions
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<br>Also, it takes in account (that can easily be overlooked) of the note after the description of the algorithm: |
<br>Also, it takes in account (that can easily be overlooked) of the note after the description of the algorithm: |
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<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. |
<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. |
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<lang rexx>/*REXX program plots/draws a line using the Xiaolin Wu line algorithm. |
<lang rexx>/*REXX program plots/draws (ASCII) a line using the Xiaolin Wu line algorithm. */ |
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background='·' /*background character: a middle-dot. */ |
background= '·' /*background character: a middle-dot. */ |
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image.=background /*fill the array with middle-dots. */ |
image.= background /*fill the array with middle-dots. */ |
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plotC='░▒▓█' /*characters used for plotting points. */ |
plotC= '░▒▓█' /*characters used for plotting points. */ |
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EoE= |
EoE= 3000 /*EOE = End Of Earth, er, ··· graph. */ |
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do j=-EoE to +EoE /*define the graph: lowest ──► highest.*/ |
do j=-EoE to +EoE /*define the graph: lowest ──► highest.*/ |
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image.j.0='─' /*define the graph's horizontal axis. */ |
image.j.0= '─' /*define the graph's horizontal axis. */ |
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image.0.j='│' /* " " " verical " */ |
image.0.j= '│' /* " " " verical " */ |
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end /*j*/ |
end /*j*/ |
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image.0.0='┼' /*define the graph's axis origin (char)*/ |
image.0.0= '┼' /*define the graph's axis origin (char)*/ |
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parse arg xi yi xf yf . /*allow specifying the line-end points.*/ |
parse arg xi yi xf yf . /*allow specifying the line-end points.*/ |
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if xi=='' | xi=="," then xi= 1 /*Not specified? Then use the default.*/ |
if xi=='' | xi=="," then xi= 1 /*Not specified? Then use the default.*/ |
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if yi=='' | yi=="," then yi= 2 /* " " " " " " */ |
if yi=='' | yi=="," then yi= 2 /* " " " " " " */ |
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if xf=='' | xf=="," then xf=11 /* " " " " " " */ |
if xf=='' | xf=="," then xf=11 /* " " " " " " */ |
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if yf=='' | yf=="," then yf=12 /* " " " " " " */ |
if yf=='' | yf=="," then yf=12 /* " " " " " " */ |
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minX=0; minY=0 /*use these as the limits for plotting.*/ |
minX=0; minY=0 /*use these as the limits for plotting.*/ |
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maxX=0; maxY=0 /* " " " " " " " */ |
maxX=0; maxY=0 /* " " " " " " " */ |
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call drawLine xi, yi, xf, yf /*invoke subroutine and graph the line.*/ |
call drawLine xi, yi, xf, yf /*invoke subroutine and graph the line.*/ |
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border=2 /*allow additional space (plot border).*/ |
border=2 /*allow additional space (plot border).*/ |
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minX=minX-border*2; maxX=maxX+border |
minX=minX - border * 2; maxX=maxX+border * 2 /*preserve screen's aspect ratio {*2}.*/ |
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minY=minY-border ; maxY=maxY+border |
minY=minY - border ; maxY=maxY+border |
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do y=maxY |
do y=maxY to minY by -1; _= /*construct a row.*/ |
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do x=minX to maxX; _=_ || image.x.y; end /*x*/ |
do x=minX to maxX; _=_ || image.x.y; end /*x*/ |
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say _ /*display the constructed row to term. */ |
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end /*y*/ /*graph is cropped by the MINs and MAXs*/ |
end /*y*/ /*graph is cropped by the MINs and MAXs*/ |
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exit /*stick a fork in it, we're all done. */ |
exit /*stick a fork in it, we're all done. */ |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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/*────────────────────────────────────────────────────────────────────────────*/ |
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drawLine: parse arg x1,y1,x2,y2; switchXY=0; dx=x2-x1 |
drawLine: parse arg x1,y1,x2,y2; switchXY=0; dx=x2-x1 |
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dy=y2-y1 |
dy=y2-y1 |
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if abs(dx) |
if abs(dx)<abs(dy) then parse value x1 y1 x2 y2 dx dy with y1 x2 y2 x2 dy dx |
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if x2<x1 then parse value x1 x2 y1 y2 1 with x2 x1 y2 y1 switchXY |
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if x2<x1 then parse value x1 x2 y1 y2 1 with, |
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x2 x1 y2 y1 switchXY |
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gradient=dy/dx |
gradient=dy/dx |
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xend=round(x1) /*◄─────────────────1st endpoint.══════════════*/ |
xend=round(x1) /*◄─────────────────1st endpoint.══════════════*/ |
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yend=y1 + gradient*(xend-x1); xgap=1-fpart(x1 + .5) |
yend=y1 + gradient * (xend-x1); xgap=1 - fpart(x1 + .5) |
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xpx11=xend; ypx11=floor(yend) |
xpx11=xend; ypx11=floor(yend) |
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intery=yend+gradient |
intery=yend+gradient |
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call plotXY xpx11, ypx11, brite(1-fpart(yend*xgap)), switchXY |
call plotXY xpx11, ypx11, brite(1 - fpart(yend*xgap)), switchXY |
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call plotXY xpx11, ypx11+1, brite( fpart(yend*xgap)), switchXY |
call plotXY xpx11, ypx11+1, brite( fpart(yend*xgap)), switchXY |
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xend=round(x2) /*◄─────────────────2nd endpoint.══════════════*/ |
xend=round(x2) /*◄─────────────────2nd endpoint.══════════════*/ |
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yend=y2 + gradient*(xend-x2); xgap=fpart(x2 + .5) |
yend=y2 + gradient * (xend-x2); xgap= fpart(x2 + .5) |
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xpx12=xend; ypx12=floor(yend) |
xpx12=xend; ypx12=floor(yend) |
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call plotXY xpx12, ypx12 , brite(1-fpart(yend*xgap)), switchXY |
call plotXY xpx12, ypx12 , brite(1 - fpart(yend*xgap)), switchXY |
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call plotXY xpx12, ypx12+1, brite( fpart(yend*xgap)), switchXY |
call plotXY xpx12, ypx12+1, brite( fpart(yend*xgap)), switchXY |
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do x=xpx11+1 to xpx12-1 /*◄───draw the line.═════════════*/ |
do x=xpx11+1 to xpx12-1 /*◄───draw the line.═════════════*/ |
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!intery=floor(intery) |
!intery=floor(intery) |
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call plotXY x, !intery , brite(1-fpart(intery)), switchXY |
call plotXY x, !intery , brite(1 - fpart(intery)), switchXY |
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call plotXY x, !intery+1, brite( fpart(intery)), switchXY |
call plotXY x, !intery+1, brite( fpart(intery)), switchXY |
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intery=intery+gradient |
intery=intery + gradient |
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end /*x*/ |
end /*x*/ |
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return |
return |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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/*────────────────────────────────short subroutines and functions.────────────*/ |
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brite: return substr(background||plotC, 1+round(abs(arg(1))*length(plotC)),1) |
brite: return substr(background || plotC, 1 + round( abs( arg(1) ) * length(plotC)), 1) |
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floor: parse arg ?; _=trunc(?); return _ - (?<0) * (?\=_) |
floor: parse arg ?; _=trunc(?); return _ - (?<0) * (?\=_) |
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fpart: parse arg ?; return abs(? - trunc(?)) |
fpart: parse arg ?; return abs(? - trunc(?)) |
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round: return format(arg(1), , word(arg(2) 0, 1)) |
round: return format(arg(1), , word(arg(2) 0, 1) ) |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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plotXY: parse arg xx,yy,bc,switchYX; if switchYX then parse arg yy,xx |
plotXY: parse arg xx,yy,bc,switchYX; if switchYX then parse arg yy,xx |
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image.xx.yy=bc; minX=min(minX,xx); maxX=max(maxX,xx) |
image.xx.yy=bc; minX=min(minX, xx); maxX=max(maxX,xx) |
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minY=min(minY,yy); maxY=max(maxY,yy) |
minY=min(minY, yy); maxY=max(maxY,yy); return</lang> |
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| ⚫ | |||
return</lang> |
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| ⚫ | |||
<pre> |
<pre> |
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