Created
June 23, 2011 04:56
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Draw simple shapes with points.
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<!doctype html> | |
<html> | |
<head> | |
<title>Shape Maker</title> | |
<style type="text/css"> | |
body { | |
font-family: Helvetica, Arial, sans-serif; | |
line-height: 1.5em; | |
font-size: 14px; | |
} | |
#canvas { | |
display: block; | |
width: 100%; | |
height: 70%; | |
border: 1px solid black; | |
} | |
#instructions { | |
float: left; | |
width: 40%; | |
} | |
#options1 { | |
float: left; | |
width: 30%; | |
} | |
#options2 { | |
float: left; | |
} | |
#grid-size { | |
width: 2em; | |
} | |
</style> | |
</head> | |
<body> | |
<canvas id="canvas" width="640" height="480"></canvas> | |
<p id="instructions">Click to drag points.<br> | |
Control-click to add points.<br> | |
Shift-click to remove points.</p> | |
<p id="options1"> | |
Snap to grid: <input type="checkbox" id="snap-to-grid"><br> | |
Grid size: <input id="grid-size" value="12"> | |
</p> | |
<p id="options2"> | |
<button id="export-btn">Export</button> | |
<pre id="export-data"></pre> | |
</p> | |
<script> | |
function $(id) { | |
return document.getElementById(id); | |
} | |
var canvas = $("canvas"); | |
var ctx = canvas.getContext("2d"); | |
//ctx.translate(.5, .5); | |
var points = []; | |
ctx.fillStyle = "#cc0000"; | |
var pointSize = 4; | |
var radius = pointSize / 2; | |
var snapToGrid = false; | |
var gridSize = 12; | |
function redraw() { | |
ctx.clearRect(0, 0, canvas.width, canvas.height); | |
if (points[0]) ctx.moveTo(points[0][0], points[0][1]); | |
ctx.beginPath(); | |
points.forEach(function (point) { | |
ctx.lineTo(point[0], point[1]); | |
ctx.fillRect(point[0] - radius, | |
point[1] - radius, pointSize, pointSize); | |
}); | |
ctx.closePath(); | |
ctx.stroke(); | |
} | |
function pointAt(x, y) { | |
for (var i = 0; i < points.length; i++) { | |
var point = points[i]; | |
if (Math.abs(point[0] - x) <= radius && | |
Math.abs(point[1] - y) <= radius) { | |
return point; | |
} | |
} | |
} | |
function addPoint(point) { | |
points.push(point); | |
redraw(); | |
} | |
function removePoint(point) { | |
var i = points.indexOf(point); | |
if (~i) { | |
points.splice(i, 1); | |
} | |
redraw(); | |
} | |
function snap(x, y) { | |
if (snapToGrid) { | |
x = Math.round(x / gridSize) * gridSize; | |
y = Math.round(y / gridSize) * gridSize; | |
} | |
return [x, y]; | |
} | |
var dragTarget; // point being tragged | |
canvas.addEventListener("mousedown", function (e) { | |
var x = e.offsetX; | |
var y = e.offsetY; | |
if (e.ctrlKey) { | |
var point = snap(x, y); | |
addPoint(point); | |
startDraggingPoint(point); | |
} else if (e.shiftKey) { | |
var point = pointAt(x, y); | |
if (point) { | |
removePoint(point); | |
} | |
} else { | |
var point = pointAt(x, y); | |
if (point) { | |
startDraggingPoint(point); | |
} | |
} | |
}, false); | |
canvas.addEventListener("contextmenu", function (e) { | |
e.preventDefault(); | |
}, false); | |
function startDraggingPoint(point) { | |
dragTarget = point; | |
canvas.addEventListener("mousemove", mouseMoveWithPoint, false); | |
window.addEventListener("mouseup", mouseUpWithPoint, false); | |
} | |
function mouseMoveWithPoint(e) { | |
var snapped = snap(e.offsetX, e.offsetY); | |
dragTarget[0] = snapped[0]; | |
dragTarget[1] = snapped[1]; | |
redraw(); | |
} | |
function mouseUpWithPoint(e) { | |
dragTarget = null; | |
canvas.removeEventListener("mousemove", mouseMoveWithPoint, false); | |
window.removeEventListener("mouseup", mouseUpWithPoint, false); | |
} | |
function updateSize() { | |
canvas.width = canvas.offsetWidth; | |
canvas.height = canvas.offsetHeight; | |
redraw(); | |
} | |
updateSize(); | |
window.addEventListener("resize", updateSize); | |
$("snap-to-grid").addEventListener("change", function (e) { | |
snapToGrid = !!this.value; | |
}, false); | |
$("grid-size").addEventListener("keyup", function (e) { | |
gridSize = ~~this.value; | |
}, false); | |
$("export-btn").addEventListener("click", function (e) { | |
$("export-data").innerHTML = JSON.stringify(points); | |
}, false); | |
</script> | |
</body> | |
</html> |
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