GIS 演算法，計算箭頭

根據兩個點，計算箭頭。

var x2 = points[length - 1].x;

var y2 = points[length - 1].y;

var x1 = points[length - 2].x;

var y1 = points[length - 2].y;

var distance = math.sqrt(math.pow((x2 - x1),2) + math.pow((y2 - y1),2));

var yb = y2 - s * (x2 - x1) / (math.sqrt2 * distance) + s * (y1 - y2) / (math.sqrt2 * distance);

var xb = x2 - s * (x2 - x1) / (math.sqrt2 * distance) - s * (y1 - y2) / (math.sqrt2 * distance);

var ya = y2 + s * (x2 - x1) / (math.sqrt2 * distance) + s * (y1 - y2) / (math.sqrt2 * distance);

var xa = x2 - s * (x2 - x1) / (math.sqrt2 * distance) + s * (y1 - y2) / (math.sqrt2 * distance);

feature.geometry.components.push(new openlayers.geometry.point(xa, ya));

feature.geometry.components.push(new openlayers.geometry.point(x2, y2));

feature.geometry.components.push(new openlayers.geometry.point(xb, yb));

/*var x1 = points[length - 1].x;

var y1 = points[length - 1].y;

var x2 = points[length - 2].x;

var y2 = points[length - 2].y;

if (x2 != x1)

var angler = angle + math.pi / 4;

}else

} else

}else

}} else

var xn1 = x1 + s * math.sin(anglel);

var yn1 = y1 + s * math.cos(anglel);

var xn2 = x1 + s * math.sin(angler);

var yn2 = y1 + s * math.cos(angler);

feature.geometry.components.push(new openlayers.geometry.point(xn1, yn1));

feature.geometry.components.push(new openlayers.geometry.point(x1, y1));

feature.geometry.components.push(new openlayers.geometry.point(xn2, yn2));*/

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