wuline.js

// integer part of x
function ipart(x) {
	return Math.floor(x);
}

function round(x) {
	return Math.round(x);
}

// fractional part of x
function fpart(x) {
	return x - Math.floor(x);
}

function rfpart(x) {
	return 1 - fpart(x);
}

function plot(x, y, c) {
	x=x|0;
	y=y|0;
  // plot the pixel at (x, y) with brightness c (where 0 ≤ c ≤ 1)
  ctx.fillStyle="rgba(0,0,0,{{c}})".hairlip({c:(c)});
  ctx.fillRect(x*pxSize, y*pxSize, pxSize, pxSize);
}






function plotPair (x, y, weight, steep, xgap) {
	if(steep) {
		plot(y    , x, xgap * (1 - weight));
		plot(y + 1, x, xgap * weight);
	} else {
		plot(x, y  , xgap * (1 - weight));
		plot(x, y+1, xgap * weight);
	}

}


//generate an array of input for plotpair
var lookuptable = {};
function makeLineIterator(x0,y0,x1,y1){
	var steep = Math.abs(y1 - y0) > Math.abs(x1 - x0);

	function midpoint(xp1, x, y, slope, steep,  xgap) {
		var xint = round(x);
		var yint = y + slope * ( xint - xp1 );
		return  [	xint,	ipart(yint),	fpart(yint),	steep,	xgap]
	}
	function makeSublineIterator(x0,y0,x1,y1,steep) {
		var slope = (y1 - y0) / (x1 - x0);
		var intery =  slope * (round(x0) - x0) + slope + y0  // first y-intersection for the main loop
		var xp1 = round(x0);
		var xp2 = round(x1);
		var x = xp1-1;
		return {
			next: function() {
				x+=1;
				if (x === xp1)         	return {value: midpoint(	xp1,    x0,	y0,    	slope,	steep,	rfpart(x0 + 0.5)	),	done: false};
				if (x > xp1 && x < xp2)	return {value: midpoint(	xp1+1,  x, 	intery,	slope,	steep,	1               	),	done: false};
				if (x === xp2)         	return {value: midpoint(	xp2,    x1,	y1,    	slope,	steep,	fpart(x1 + 0.5) 	),	done: false};
				if (x > xp2)           	return {done: true};
			}
		}
	}

	return steep ? 
	y0 > y1 ? 
	makeSublineIterator(y1,x1,y0,x0,steep) : 
	makeSublineIterator(y0,x0,y1,x1,steep) :
	x0 > x1 ? 
	makeSublineIterator(x1,y1,x0,y0,steep) : 
	makeSublineIterator(x0,y0,x1,y1,steep)

}