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2_15_rubberband_lines.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Rubberband lines</title>
<style type="text/css">
body {
background: #eee;
}
#controls {
position: absolute;
left: 25px;
top: 25px;
}
#canvas {
background: #fff;
cursor: pointer;
margin: 10px 0 0 10px;
-webkit-box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
-moz-box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
}
</style>
</head>
<body>
<canvas id="canvas" width="600" height="400"></canvas>
<div id="controls">
Stroke color: <select name="" id="strokeStyleSelect">
<option value="red">red</option>
<option value="green">green</option>
<option value="blue">blue</option>
<option value="orange">orange</option>
<option value="cornflowerblue">conflowerblue</option>
<option value="goldenrod">goldenrod</option>
<option value="navy">navy</option>
<option value="purple">purple</option>
</select>
Guidewires:
<input type="checkbox" id="guidewireCheckbox" checked="checked">
<input type="button" id="eraseAllButton" value="Erase All">
</div>
</body>
<script type="text/javascript">
var cvs = document.getElementById('canvas'),
ctx = cvs.getContext('2d'),
eraseAllButton = document.getElementById('eraseAllButton'),
strokeStyleSelect = document.getElementById('strokeStyleSelect'),
guidewireCheckbox = document.getElementById('guidewireCheckbox'),
drawingSurfaceImageData,
mousedown = {},
rubberbandRect = {},
dragging = false,
guidewires = guidewireCheckbox.checked;
function drawGrid (ctx, color, stepx, stepy) {
ctx.save();
ctx.strokeStyle = color;
ctx.lineWidth = 0.5;
for(var i = stepx + 0.5; i < ctx.canvas.width; i += stepx) {
ctx.beginPath();
ctx.moveTo(i, 0);
ctx.lineTo(i, ctx.canvas.height);
ctx.stroke();
}
for(var i = stepy + 0.5; i < ctx.canvas.height; i += stepy) {
ctx.beginPath();
ctx.moveTo(0, i);
ctx.lineTo(ctx.canvas.width, i);
ctx.stroke();
}
ctx.restore();
}
function windowToCanvas (x, y) {
var bbox = cvs.getBoundingClientRect();
return {
x : x - bbox.left * (cvs.width / bbox.width),
y : y - bbox.top * (cvs.height/ bbox.height)
}
}
// save and restore drawing surface
function saveDrawingSurface () {
drawingSurfaceImageData = ctx.getImageData(0, 0, cvs.width, cvs.height);
}
function restoreDrawingSurface () {
ctx.putImageData(drawingSurfaceImageData, 0, 0);
}
// Rubber bands
function updateRubberbandRectangle (loc) {
rubberbandRect.width = Math.abs(loc.x - mousedown.x);
rubberbandRect.height = Math.abs(loc.y - mousedown.y);
if(loc.x > mousedown.x) { rubberbandRect.left = mousedown.x; }
else { rubberbandRect.left = loc.x; }
if(loc.y > mousedown.y) { rubberbandRect.top = mousedown.y; }
else { rubberbandRect.top = loc.y; }
}
function drawRubberbandShape (loc) {
ctx.beginPath();
ctx.moveTo(mousedown.x, mousedown.y);
ctx.lineTo(loc.x, loc.y);
ctx.stroke();
}
function updateRubberband (loc) {
updateRubberbandRectangle(loc);
drawRubberbandShape(loc);
}
// Guidewires
function drawHorizontalLine(y) {
ctx.beginPath();
ctx.moveTo(0, y + 0.5);
ctx.lineTo(ctx.canvas.width, y + 0.5);
ctx.stroke();
}
function drawVerticalLine(x) {
ctx.beginPath();
ctx.moveTo(x + 0.5, 0);
ctx.lineTo(x + 0.5, ctx.canvas.height);
ctx.stroke();
}
function drawGuidewires (x, y) {
ctx.save();
ctx.strokeStyle = 'rgba(0, 0, 230, 0.4)';
ctx.lineWidth = 0.5;
drawVerticalLine(x);
drawHorizontalLine(y);
ctx.restore();
}
// Canvas event handlers
cvs.onmousedown = function(e) {
var loc = windowToCanvas(e.clientX, e.clientY);
e.preventDefault(); // prevent cursor change
saveDrawingSurface();
mousedown.x = loc.x;
mousedown.y = loc.y;
dragging = true;
}
cvs.onmousemove = function(e) {
var loc;
if(dragging) {
e.preventDefault(); // Prevent selections
loc = windowToCanvas(e.clientX, e.clientY);
restoreDrawingSurface();
updateRubberband(loc);
if(guidewires) {
drawGuidewires(loc.x, loc.y);
}
}
}
cvs.onmouseup = function(e) {
loc = windowToCanvas(e.clientX, e.clientY);
restoreDrawingSurface();
updateRubberband(loc);
dragging = false;
}
// Controls event handlers
eraseAllButton.onclick = function(e) {
ctx.clearRect(0, 0, cvs.width, cvs.height);
drawGrid(ctx, 'lightgray', 10, 10);
saveDrawingSurface();
}
strokeStyleSelect.onchange = function(e) {
ctx.strokeStyle = strokeStyleSelect.value;
}
guidewireCheckbox.onchange = function(e) {
guidewires = guidewireCheckbox.checked;
}
// Initialization
ctx.strokeStyle = strokeStyleSelect.value;
console.log(strokeStyleSelect.value);
drawGrid(ctx, 'lightgray', 10, 10);
</script>
</html>