Bitmap/Bresenham's line algorithm: Difference between revisions
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As a structured script. |
As a structured script. |
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<syntaxhighlight lang="ada">#!/usr/local/bin/spar |
<syntaxhighlight lang="ada">#!/usr/local/bin/spar |
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pragma annotate( summary, "DrawLine" ) |
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=={{header|SparForte}}== |
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@( description, "Draw a line given 2 points with the Bresenham's algorithm." ) |
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As a structured script. |
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@( see_also, "http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm" ) |
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<syntaxhighlight lang="ada">#!/usr/local/bin/spar |
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@( author, "Ken O. Burtch" ); |
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</syntaxhighlight></syntaxhighlight> |
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pragma license( unrestricted ); |
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pragma restriction( no_external_commands ); |
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procedure drawline is |
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-- Spar 1.x has only single-dimensional arrays but we can simulate a |
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-- two dimensional array that has been folded into a 1D array |
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width : constant positive := 20; |
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height : constant positive := 20; |
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type image_array is array(1..400) of character; |
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Picture : image_array; |
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-- Line |
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-- Draw a line between two coordinates using the given character |
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procedure Line ( Start_X : positive; Start_Y : positive; Stop_X : positive; Stop_Y : positive; Color : character) is |
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-- at this point, formal parameters are defined but the actual values aren't defined! |
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-- but creating a dummy Line in a test script works? |
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DX : constant float := abs( float( Stop_X ) - float( Start_X ) ); |
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DY : constant float := abs( float( Stop_Y ) - float( Start_Y ) ); |
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Err : float; |
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X : positive := Start_X; |
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Y : positive := Start_Y; |
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Step_X : integer := 1; |
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Step_Y : integer := 1; |
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begin |
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if Start_X > Stop_X then |
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Step_X := -1; |
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end if; |
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if Start_Y > Stop_Y then |
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Step_Y := -1; |
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end if; |
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if DX > DY then |
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Err := DX / 2.0; |
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while X /= Stop_X loop |
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Picture (X + width*(Y-1)) := Color; |
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Err := @ - DY; |
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if Err < 0.0 then |
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Y := positive( integer(@) + Step_Y); |
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Err := @ + DX; |
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end if; |
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X := positive( integer(@) + Step_X ); |
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end loop; |
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else |
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Err := DY / 2.0; |
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while Y /= Stop_Y loop |
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Picture (X + height*(Y-1)) := Color; |
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Err := @ - DX; |
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if Err < 0.0 then |
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X := positive( integer(@) + Step_X ); |
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Err := @ + DY; |
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end if; |
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Y := positive( integer(@) + Step_Y ); |
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end loop; |
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end if; |
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Picture (X + width*(Y-1)) := Color; |
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end Line; |
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-- new_picture |
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-- Erase the picture by filling it with spaces. |
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procedure new_picture is |
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begin |
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for i in arrays.first( Picture )..arrays.last( Picture ) loop |
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Picture(i) := ' '; |
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end loop; |
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end new_picture; |
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-- render |
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-- Draw the contents of the picture area. |
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procedure render is |
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begin |
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for i in arrays.first( Picture )..arrays.last( Picture ) loop |
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put( Picture(i) ); |
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if i mod width = 0 then |
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new_line; |
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end if; |
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end loop; |
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end render; |
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begin |
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new_picture; |
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Line( 1, 8, 8, 16, 'X' ); |
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Line( 8,16,16, 8, 'X' ); |
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Line(16, 8, 8, 1, 'X' ); |
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Line( 8, 1, 1, 8, 'X' ); |
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render; |
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end drawline;</syntaxhighlight> |
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=={{header|Tcl}}== |
=={{header|Tcl}}== |