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@EE2dev
Last active April 2, 2018 21:45
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affine transformations
license: mit

This block illustrate basic affine transformations with canvas.

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://d3js.org/d3.v5.min.js"></script>
<style>
body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
div#canvas {background: #000;}
</style>
</head>
<body>
<div id="canvas"></div>
<aside style="display:none">
<img id="star-texture" src="https://ee2dev.github.io/startext/lib/stars-02.png">
</aside>
<script>
const canvasWidth = 200;
const canvasHeight = 200;
const transforms = ["rotate","fade","scale","translate"];
let canvas = d3.select("div#canvas").selectAll("canvas")
.data(transforms)
.enter()
.append("canvas")
.attr("class", (d) => d)
.attr("width", canvasWidth)
.attr("height", canvasHeight);
let props = getProps(transforms);
setInterval(rotate, 50);
setInterval(fade, 50);
setInterval(translate, 50);
setInterval(scale, 50);
function getProps(_transforms) {
const arrayLength = _transforms.length;
let allProps = [];
for (let i = 0; i < arrayLength; i++) {
let prop = {};
prop.name = _transforms[i];
prop.texture = getStar(i);
prop.change = 1;
prop.sign = 1;
prop.center = {x: canvasWidth/2 - prop.texture.width/2, y: canvasHeight/2 - prop.texture.height/2};
allProps.push(prop);
}
return allProps;
}
function getStar(num) {
const texture = {
t: document.querySelector("#star-texture"),
x: 80*num,
y: 0,
width: 80,
height: 80};
return texture;
}
function rotate() {
let context = d3.select("canvas.rotate").node().getContext('2d');
context.clearRect(0, 0, canvasWidth, canvasHeight);
context.translate(canvasWidth/2, canvasHeight/2);
context.rotate(1 * Math.PI / 180);
context.translate(-canvasWidth/2, -canvasHeight/2);
context.drawImage(props[0].texture.t, props[0].texture.x, props[0].texture.y,
props[0].texture.width, props[0].texture.height, props[0].center.x, props[0].center.y,
props[0].texture.width, props[0].texture.height);
}
function translate() {
let context = d3.select("canvas.translate").node().getContext('2d');
props[1].change = (props[1].sign === 1) ? props[1].change + 1 : props[1].change - 1;
if (Math.abs(props[1].change) > (canvasWidth - props[1].texture.width) / 2) {
props[1].sign = props[1].sign * -1;
props[1].change = 0;
}
context.clearRect(0, 0, canvasWidth, canvasHeight);
context.translate(props[1].sign, 0);
context.drawImage(props[1].texture.t, props[1].texture.x, props[1].texture.y,
props[1].texture.width, props[1].texture.height, props[1].center.x, props[1].center.y,
props[1].texture.width, props[1].texture.height);
}
function fade() {
let context = d3.select("canvas.fade").node().getContext('2d');
props[2].change = (props[2].sign === 1) ? props[2].change - 0.05 : props[2].change + 0.05;
if (props[2].change < 0 || props[2].change > 1) {props[2].sign = props[2].sign * -1;}
context.clearRect(0, 0, canvasWidth, canvasHeight);
context.globalAlpha = props[2].change;
context.drawImage(props[2].texture.t, props[2].texture.x, props[2].texture.y,
props[2].texture.width, props[2].texture.height, props[2].center.x, props[2].center.y,
props[2].texture.width, props[2].texture.height);
}
function scale() {
let context = d3.select("canvas.scale").node().getContext('2d');
props[3].change = (props[3].sign === 1) ? props[3].change + 1 : props[3].change - 1;
let sg = props[3].sign * props[3].change;
if (Math.pow(0.97, sg) < 0.05 || Math.pow(0.97, sg) > 1) {
props[3].sign = props[3].sign * -1;
props[3].change = 0;
}
let s = Math.pow(0.97, props[3].sign);
context.clearRect(0, 0, canvasWidth, canvasHeight);
context.translate(canvasWidth/2, canvasHeight/2);
context.scale(s,s);
context.translate(-canvasWidth/2, -canvasHeight/2);
context.drawImage(props[3].texture.t, props[3].texture.x, props[3].texture.y,
props[3].texture.width, props[3].texture.height, props[3].center.x, props[3].center.y,
props[3].texture.width, props[3].texture.height);
}
</script>
</body>
</html>
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