110 lines
4.6 KiB
HTML
110 lines
4.6 KiB
HTML
|
<!doctype html>
|
||
|
|
<html lang="en">
|
||
|
|
|
||
|
|
<head>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<title>Coordinates Doctest</title>
|
||
|
|
<link rel="stylesheet" href="../lib/3rdparty/highlight/styles/default.css">
|
||
|
|
<link rel="stylesheet" href="../css/doctest.css">
|
||
|
|
<script src="./3rdparty/highlight/highlight.pack.js"></script>
|
||
|
|
<script src="./3rdparty/all.js"></script>
|
||
|
|
<script src="all.js"></script>
|
||
|
|
<script>
|
||
|
|
function drawPolygons() {
|
||
|
|
canvas.width = main.getBoundingClientRect().width
|
||
|
|
let context = canvas.getContext('2d')
|
||
|
|
context.clearRect(0, 0, canvas.width, canvas.height)
|
||
|
|
|
||
|
|
let stage = scatterContainer.polygon
|
||
|
|
stage.draw(context, { stroke: '#FF0000' })
|
||
|
|
for (let scatter of scatterContainer.scatter.values()) {
|
||
|
|
let polygon = scatter.polygon
|
||
|
|
polygon.draw(context, { stroke: '#FF0000' })
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
function animate(callback) {
|
||
|
|
requestAnimationFrame((dt) => {
|
||
|
|
drawPolygons()
|
||
|
|
callback()
|
||
|
|
animate(callback)
|
||
|
|
})
|
||
|
|
}
|
||
|
|
</script>
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body onload="Doctest.run()">
|
||
|
|
<h1>
|
||
|
|
Coordinates
|
||
|
|
</h1>
|
||
|
|
<p>
|
||
|
|
To position objects in defined spatial relationships presupposes a clear understanding of the involved coordinate systems.
|
||
|
|
Unfortunately, several systems with several conventions are involved:
|
||
|
|
<a href="https://javascript.info/coordinates">DOM & CSS</a>,
|
||
|
|
<a href="https://www.sarasoueidan.com/blog/svg-coordinate-systems/SVG">SVG</a>,
|
||
|
|
<a href="https://www.w3schools.com/graphics/canvas_coordinates.asp">Canvas</a>
|
||
|
|
</p>
|
||
|
|
<p>
|
||
|
|
We need a common reference system to switch between these coordinate systems. As the uttermost context, the browser page
|
||
|
|
coordinate system is the most natural one. A simple API was long missing but has now been established in most modern
|
||
|
|
browsers with
|
||
|
|
<a href="https://developer.mozilla.org/en-US/docs/Web/API/Window/convertPointFromNoteToPage">window.convertPointFromNoteToPage</a> and the inverse
|
||
|
|
<a href="https://developer.mozilla.org/en-US/docs/Web/API/Window/convertPointFromPageToNode">window.convertPointFromPageToNode</a>.
|
||
|
|
Although MDN Web Docs warns about their Non-standard nature the methods work in browsers targeted
|
||
|
|
by the IWM Browser project. This doctest assures that this assumption can be tested.
|
||
|
|
</p>
|
||
|
|
<p>Let's look at a scatter object with a rotatable local coordinate system. We try to follow a point in this local coordinate
|
||
|
|
system by showing a marker outside the scatter that follows the point.
|
||
|
|
</p>
|
||
|
|
<div id="main" class="grayBorder interactive" style="position: relative; width: 100%; height: 280px;">
|
||
|
|
<!-- Note that we need to set draggable to false to avoid conflicts. The DOM elements
|
||
|
|
must also be positioned absolutely. -->
|
||
|
|
<img id="women" draggable="false" style="position: absolute;" src="examples/women.jpeg" />
|
||
|
|
|
||
|
|
<canvas id="canvas" height="280" style="z-index: 100000; pointer-events: none; position: absolute; border: 1px solid red;">
|
||
|
|
Canvas not supported.
|
||
|
|
</canvas>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<script class="doctest">
|
||
|
|
let dx = 44
|
||
|
|
|
||
|
|
let app = new App()
|
||
|
|
let scatterContainer = new DOMScatterContainer(main)
|
||
|
|
let angle = 15
|
||
|
|
let image = document.getElementById('women')
|
||
|
|
// The DOMScatter needs initial width and height. Therefore we
|
||
|
|
// define the scatter when the image size is known, i.e. after loading...
|
||
|
|
image.onload = (e) => {
|
||
|
|
let scatter = new DOMScatter(image, scatterContainer, {
|
||
|
|
x: dx,
|
||
|
|
y: 44,
|
||
|
|
width: e.target.naturalWidth,
|
||
|
|
height: e.target.naturalHeight,
|
||
|
|
rotationDegrees: angle,
|
||
|
|
throwVisibility: 88,
|
||
|
|
minScale: 0.5,
|
||
|
|
maxScale: 1.5
|
||
|
|
})
|
||
|
|
dx += 300
|
||
|
|
angle = -angle
|
||
|
|
}
|
||
|
|
|
||
|
|
app.run()
|
||
|
|
|
||
|
|
function followPoint() {
|
||
|
|
let context = canvas.getContext('2d')
|
||
|
|
let localPoint = { x: 100, y: 100 }
|
||
|
|
let globalPoint = convertPointFromNodeToPage(image, localPoint.x, localPoint.y)
|
||
|
|
let canvasPoint = convertPointFromPageToNode(canvas, globalPoint.x, globalPoint.y)
|
||
|
|
|
||
|
|
context.strokeStyle = 'red'
|
||
|
|
context.beginPath()
|
||
|
|
context.arc(canvasPoint.x, canvasPoint.y, 12, 0, Math.PI * 2)
|
||
|
|
context.stroke()
|
||
|
|
|
||
|
|
}
|
||
|
|
animate(followPoint)
|
||
|
|
</script>
|
||
|
|
|
||
|
|
</body>
|