Bitmap/Bresenham's line algorithm: Difference between revisions
Content deleted Content added
No edit summary |
m →version 1: added/changed whitespace and comments, optimized a subroutine. |
||
| Line 2,591: | Line 2,591: | ||
===version 1=== |
===version 1=== |
||
This REXX version has automatic scaling (for displaying the plot) and handles multiple line segments. |
This REXX version has automatic scaling (for displaying the plot) and handles multiple line segments. |
||
<lang rexx>/*REXX program plots/draws line |
<lang rexx>/*REXX program plots/draws line segments using the Bresenham's line algorithm.*/ |
||
@.='·' /*fill the array with middle─dots*/ |
@.='·' /*fill the array with middle─dots chars*/ |
||
parse arg data /*allow data point specifications*/ |
parse arg data /*allow the data point specifications. */ |
||
if data='' then data= '(1,8) (8,16) (16,8) (8,1) (1,8)' /* |
if data='' then data= '(1,8) (8,16) (16,8) (8,1) (1,8)' /*◄────rhombus.*/ |
||
data=translate(data,,'()[]{}/,:;') /*elide chaff from data points. */ |
data=translate(data,,'()[]{}/,:;') /*elide chaff from the data points. */ |
||
/* [↓] data |
/* [↓] data point pairs ───► !.array. */ |
||
do points=1 while data\='' /*put data points into an array |
do points=1 while data\='' /*put the data points into an array (!)*/ |
||
parse var data x y data; !.points=x y /*extract line segments.*/ |
parse var data x y data; !.points=x y /*extract the line segments. */ |
||
if points==1 then do; minX=x; maxX=x; minY=y; maxY=y; end /*1st case*/ |
if points==1 then do; minX=x; maxX=x; minY=y; maxY=y; end /*1st case.*/ |
||
minX=min(minX,x); maxX=max(maxX,x); minY=min(minY,y); maxY=max(maxY,y) |
minX=min(minX,x); maxX=max(maxX,x); minY=min(minY,y); maxY=max(maxY,y) |
||
end /*points*/ /* [↑] data points pairs in !. */ |
end /*points*/ /* [↑] data points pairs in array !. */ |
||
border=2 /*border |
border=2 /*border: is extra space around plot. */ |
||
minX=minX-border*2; maxX=maxX+border*2 /*min |
minX=minX-border*2; maxX=maxX+border*2 /*min and max X for the plot display.*/ |
||
minY=minY-border ; maxY=maxY+border /* " " Y " " " " */ |
minY=minY-border ; maxY=maxY+border /* " " " Y " " " " */ |
||
do x=minX to maxX; @.x.0='─'; end /*draw dash from |
do x=minX to maxX; @.x.0='─'; end /*draw a dash from left ───► right.*/ |
||
do y=minY to maxY; @.0.y='│'; end /*draw pipe from |
do y=minY to maxY; @.0.y='│'; end /*draw a pipe from lowest ───► highest*/ |
||
@.0.0='┼' /*define the plot's axis point. |
@.0.0='┼' /*define the plot's origin axis point. */ |
||
do seg=2 to points-1; _=seg-1 /*obtain the X |
do seg=2 to points-1; _=seg-1 /*obtain the X and Y line coördinates*/ |
||
call draw_line !._, !.seg /*draw (plot) a line segment. */ |
call draw_line !._, !.seg /*draw (plot) a line segment. */ |
||
end /*seg*/ /* [↑] drawing the line segments*/ |
end /*seg*/ /* [↑] drawing the line segments. */ |
||
/* [↓] display the plot to |
/* [↓] display the plot to terminal. */ |
||
do y=maxY to minY by -1; _= /*display plot one line at a time*/ |
do y=maxY to minY by -1; _= /*display the plot one line at a time. */ |
||
do x=minX to maxX /* |
do x=minX to maxX /*build line by examining the X axis.*/ |
||
_=_ || @.x.y /*construct a |
_=_ || @.x.y /*construct/build a line of the plot. */ |
||
end /*x*/ /*(a line is a "row" of points.) */ |
end /*x*/ /* (a line is a "row" of points.) */ |
||
say _ /*display a |
say _ /*display a line of the plot──►terminal*/ |
||
end /*y*/ /* [↑] all done |
end /*y*/ /* [↑] all done plotting the points. */ |
||
exit /*stick a fork in it, we're done.*/ |
exit /*stick a fork in it, we're all done. */ |
||
/*────────────────────────────────────────────────────────────────────────────*/ |
|||
/*────────────────────────────────DRAW_LINE subroutine──────────────────*/ |
|||
draw_line: procedure expose @.; parse arg x y,xf yf; plotChar='Θ' |
draw_line: procedure expose @.; parse arg x y,xf yf; plotChar='Θ' |
||
dx=abs(xf-x); if x<xf then sx=+1 /*obtain X range, determine slope*/ |
dx=abs(xf-x); if x<xf then sx=+1 /*obtain X range, determine the slope*/ |
||
else sx=-1 |
else sx=-1 |
||
dy=abs(yf-y); if y<yf then sy=+1 /*obtain Y range, determine slope*/ |
dy=abs(yf-y); if y<yf then sy=+1 /*obtain Y range, determine the slope*/ |
||
else sy=-1 |
else sy=-1 |
||
err=dx-dy /* |
err=dx-dy /*calculate error between adjustments. */ |
||
do forever; @.x.y=plotChar /*plot the points until complete.*/ |
do forever; @.x.y=plotChar /*plot the points until it's complete. */ |
||
if x=xf & y=yf then |
if x=xf & y=yf then return /*are the plot points at the finish? */ |
||
err2=err+err /* |
err2=err+err /*addition is faster than: err*2. */ |
||
if err2 > -dy then do; err=err-dy; x=x+sx; end |
if err2 > -dy then do; err=err-dy; x=x+sx; end |
||
if err2 < dx then do; err=err+dx; y=y+sy; end |
if err2 < dx then do; err=err+dx; y=y+sy; end |
||
end /*forever*/ |
end /*forever*/</lang> |
||
| ⚫ | |||
return</lang> |
|||
| ⚫ | |||
<pre> |
<pre> |
||
···│···················· |
···│···················· |
||