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<style>
body,html{margin:0;padding:0;}
#hud { position: absolute; top: 0; left: 0; pointer-events: none; }
canvas { position: absolute; top: 0; left: 0; }
</style>
<canvas id="canvas"></canvas>
<canvas id="mask"></canvas>
<div id="hud"></div>
<script src="/assets/javascripts/vendor/bower_components/jquery/dist/jquery.min.js"></script>
<script src="/assets/javascripts/vendor/bower_components/lodash/dist/lodash.min.js"></script>
<script src="/assets/javascripts/vendor/canvasutilities.js"></script>
<script src="/assets/javascripts/vendor/tube.js"></script>
<script src="/assets/javascripts/math/util.js"></script>
<script src="/assets/javascripts/math/point.js"></script>
<script src="/assets/javascripts/math/vec2.js"></script>
<script src="/assets/javascripts/util/mouse.js"></script>
<script src="/assets/javascripts/util/uid.js"></script>
<script>
var ctx = canvas.getContext('2d')
var w = mask.width = canvas.width = window.innerWidth
var h = mask.height = canvas.height = window.innerHeight
var drawing = false
var lastPoint = new point (0, 0), newPoint = new point (0, 0)
var mymouse = new mouse({
el: canvas,
down: function(e, cursor){
drawing = true
lastPoint.a = cursor.x.a
lastPoint.b = cursor.y.a
mask.clearRect(0,0,w,h)
imagedata = ctx.getImageData( 0, 0, canvas.width, canvas.height )
data = imagedata.data
},
drag: function(e, cursor){
newPoint.a = cursor.x.a
newPoint.b = cursor.x.b
},
up: function(e, cursor, new_cursor){
drawing = false
},
})
function drawLine (u, v) {
var radius = 10
var xmin = Math.min(u.a, v.a)
var ymin = Math.min(u.b, v.b)
var w = abs(u.a - v.a) + radius*2
var h = abs(u.b - v.b) + radius*2
var p = new point (0,0)
var radius2 = radius * radius
var imagedata = ctx.createImageData(w, h)
var d = imagedata.data
var i, j, t, dist
var len = sqrt(dist2(u, v))
if (len == 0) return
for (i = 0; i < w; i++) {
for (j = 0; j < h; j++) {
t = (j * w + i) * 4
p.a = i - radius + xmin
p.b = j - radius + ymin
dist = distToSegmentSquared( p, u, v, len )
if (dist > radius2) {
d[t+3] = 0
}
else {
d[t+3] = round((1 - sqrt(dist)/radius) * 255)
}
}
}
ctx.putImageData(imagedata, u.a, u.b)
}
drawLine( new point( 100, 100 ), new point( 100, 400 ) )
// drawLine( new point( 100, 100 ), new point( 400, 100 ) )
// drawLine( new point( 100, 100 ), new point( 400, 400 ) )
function sqr(x) { return x * x }
function dist2(v, w) { return sqr(v.b - w.b) + sqr(v.b - w.b) }
function distToSegmentSquared (p, v, w, len) {
var t = ((p.a - v.a) * (w.a - v.a) + (p.b - v.b) * (w.b - v.b)) / len;
if (t < 0) return dist2(p, v);
if (t > 1) return dist2(p, w);
return dist2(p, { x: v.a + t * (w.a - v.a),
y: v.b + t * (w.b - v.b) });
}
</script>
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