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Integer DDA Line drawing in JS
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function vLine( ya,yb, xa ) { | |
ya = Math.round( ya ); | |
yb = Math.round( yb ); | |
xa = Math.round( xa ); | |
var y = ya < yb ? ya : yb, | |
i = Math.abs( ya - yb ); | |
for( ; i >= 0; i-- ) { | |
console.log( 'plot', xa, y+i ); | |
} | |
} | |
function hLine( xa,xb, ya ) { | |
xa = Math.round( xa ); | |
xb = Math.round( xb ); | |
ya = Math.round( ya ); | |
var x = xa < xb ? xa : xb, | |
i = Math.abs( xa - xb ); | |
for( ; i >= 0; i-- ) { | |
console.log( 'plot', x+i, ya ); | |
} | |
} | |
function line( xa,ya, xb,yb ) { | |
xa = Math.round( xa ); | |
ya = Math.round( ya ); | |
xb = Math.round( xb ); | |
yb = Math.round( yb ); | |
var dx = xb - xa, | |
dy = yb - ya, | |
cInc, rInc, | |
h, i; | |
if( dx === 0 ) { | |
vLine( ya,yb, xa ); | |
return; | |
} else if( dy === 0 ) { | |
hLine( xa,xb, ya ); | |
return; | |
} | |
cInc = dx < 0 ? -1 : 1; | |
rInc = dy < 0 ? -1 : 1; | |
dx = Math.abs( dx ); | |
dy = Math.abs( dy ); | |
if( dx >= dy ) { | |
h = -dx; | |
console.log('plot',xa,ya); | |
for( i = dx; i > 0; i-- ) { | |
xa += cInc; | |
h += 2*dy; | |
if( h >= 0 ) { | |
ya += rInc; | |
h -= 2*dx; | |
} | |
console.log('plot',xa,ya); | |
} | |
} else { | |
h = -dy; | |
console.log('plot',xa,ya); | |
for( i = dy; i > 0; i-- ) { | |
ya += rInc; | |
h += 2*dx; | |
if( h >= 0 ) { | |
xa += cInc; | |
h -= 2*dy; | |
} | |
console.log('plot',xa,ya); | |
} | |
} | |
} | |
//line(8,3, 1,1); | |
//line(-7,3, -1,1); | |
//line(1,-1, 3,-6); | |
//line(-7,-2, -1,1); | |
//line(0,0,10,0); | |
//line(7,1, 1,3); | |
//line(1,1,1,10); | |
//line(1,1,1,1); |
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