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<html> | |
<head> | |
<title>Arbitrary Gradient Test</title> | |
<script type="text/javascript" src="graphics.js"></script> | |
<script type="text/javascript" src="math.js"></script> | |
<script type="text/javascript"> | |
function draw() { | |
var canvas = document.getElementById("canvas"); | |
var beginPoint = new Point(20, 50); | |
var beginColor = [1, 0, 0, 0.5]; // semi-opaque red | |
var endPoint = new Point(150, 200); | |
var endColor = [0, 1, 0, 1.0]; // opaque green | |
var directionalGradient = function(point) { | |
var projection = project(beginPoint, endPoint, | |
point).sub(beginPoint); | |
var beginEnd = endPoint.sub(beginPoint); | |
var lerpFac = 0; | |
if (beginEnd.normalize().add(projection.normalize()).toDist() > 1) { | |
lerpFac = projection.toDist() / beginEnd.toDist(); | |
} | |
return lerp(beginColor, endColor, lerpFac); | |
} | |
process(canvas, directionalGradient); | |
} | |
</script> | |
</head> | |
<body onload="draw()"> | |
<canvas id="canvas" width="300" height="300"></canvas> | |
</body> | |
</html> |
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function process(canvas, func) { | |
function setPixel(imageData, x, y, rgba) { | |
var index = (x + y * imageData.width) * 4; | |
for (var i = 0; i < 4; i++) { | |
imageData.data[index + i] = rgba[i] * 255; | |
} | |
} | |
var ctx = canvas.getContext("2d"); | |
var imageData = ctx.createImageData(canvas.width, | |
canvas.height); | |
for (var y = 0; y < canvas.height; y++) { | |
for (var x = 0; x < canvas.width; x++) { | |
var result = func(new Point(x, y)); | |
setPixel(imageData, x, y, result); | |
} | |
} | |
ctx.putImageData(imageData, 0, 0); | |
} |
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<html> | |
<head> | |
<title>Horizontal Gradient Test</title> | |
<script type="text/javascript" src="graphics.js"></script> | |
<script type="text/javascript" src="math.js"></script> | |
<script type="text/javascript"> | |
function draw() { | |
var canvas = document.getElementById("canvas"); | |
var leftBound = [1, 0, 0, 0.5]; // semi-opaque red | |
var rightBound = [0, 1, 0, 1.0]; // opaque green | |
var horizontalGradient = function(point) { | |
return lerp(leftBound, rightBound, point.x / canvas.width); | |
} | |
process(canvas, horizontalGradient); | |
} | |
</script> | |
</head> | |
<body onload="draw()"> | |
<canvas id="canvas" width="300" height="300"></canvas> | |
</body> | |
</html> |
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function lerp(a, b, fac) { | |
var ret = []; | |
for (var i = 0; i < Math.min(a.length, b.length); i++) { | |
ret[i] = a[i] * (1 - fac) + b[i] * fac; | |
} | |
return ret; | |
} | |
function project(target, initial, current) { | |
var delta = initial.sub(target); | |
if( (delta.x == 0) && (delta.y == 0) ) { | |
return target; | |
} | |
var t = current.sub(target).mul(delta).div(delta.toDistSquared()); | |
return delta.mul(t.x + t.y).add(target); | |
} | |
function dot(a, b) { | |
return a.x * b.x + a.y * b.y; | |
} | |
function Point(x, y) { | |
this.init(x, y); | |
} | |
Point.prototype = { | |
init: function(x, y) { | |
this.x = x? x: 0; | |
this.y = y? y: 0; | |
}, | |
add: function(other) { | |
return this.operationTemplate(other, function(a, b) {return a + b}); | |
}, | |
sub: function(other) { | |
return this.operationTemplate(other, function(a, b) {return a - b}); | |
}, | |
mul: function(other) { | |
return this.operationTemplate(other, function(a, b) {return a * b}); | |
}, | |
div: function(other) { | |
return this.operationTemplate(other, function(a, b) {return a / b}); | |
}, | |
ceil: function() { | |
return this.operationTemplate(null, function(a) {return Math.ceil(a)}); | |
}, | |
floor: function() { | |
return this.operationTemplate(null, function(a) {return Math.floor(a)}); | |
}, | |
round: function() { | |
return this.operationTemplate(null, function(a) {return Math.round(a)}); | |
}, | |
operationTemplate: function(other, op) { | |
if(isNumber(other)) { | |
return new Point(op(this.x, other), op(this.y, other)); | |
} | |
if(other == null) { | |
return new Point(op(this.x), op(this.y)); | |
} | |
return new Point(op(this.x, other.x), op(this.y, other.y)); | |
}, | |
toDist: function() { | |
return Math.sqrt(this.toDistSquared()); | |
}, | |
toDistSquared: function() { | |
return this.x * this.x + this.y * this.y; | |
}, | |
normalize: function() { | |
return this.div(this.toDist()); | |
}, | |
invert: function() { | |
return new Point(-this.x, -this.y); | |
} | |
} | |
function isNumber(n) { | |
return !isNaN(parseFloat(n)) && isFinite(n); | |
} |
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<html> | |
<head> | |
<title>Vertical Gradient Test</title> | |
<script type="text/javascript" src="graphics.js"></script> | |
<script type="text/javascript" src="math.js"></script> | |
<script type="text/javascript"> | |
function draw() { | |
var canvas = document.getElementById("canvas"); | |
var topBound = [1, 0, 0, 0.5]; // semi-opaque red | |
var bottomBound = [0, 1, 0, 1.0]; // opaque green | |
var verticalGradient = function(point) { | |
return lerp(topBound, bottomBound, point.y / canvas.height); | |
} | |
process(canvas, verticalGradient); | |
} | |
</script> | |
</head> | |
<body onload="draw()"> | |
<canvas id="canvas" width="300" height="300"></canvas> | |
</body> | |
</html> |
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