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Full-window, proper aspect HTML5 canvas example
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<!DOCTYPE html> | |
<html> | |
<head> | |
<meta charset="UTF-8"> | |
<title>Full-screen Canvas</title> | |
</head> | |
<body style="background:black"> | |
<canvas id="canvas" style="position:fixed;background:green;"> | |
Sorry, your browser does not appear to support HTML5 Canvas element. | |
</canvas> | |
<script src="FullScreenCanvas.js"></script> | |
<noscript> | |
Sorry, your browser does not appear to support Javascript. | |
</noscript> | |
</body> | |
</html> |
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////////////////////// | |
// CONSTANTS | |
var VIEWPORT_X = 1280; | |
var VIEWPORT_Y = 720; | |
var TARGET_RATIO = VIEWPORT_X / VIEWPORT_Y; | |
//////////////////////// | |
// GLOBAL VARIABLES | |
var canvas = document.getElementById("canvas"); | |
var context = canvas.getContext("2d"); | |
//////////////////////// | |
// FUNCTIONS | |
function resizeCanvas() { | |
// This function resizes the canvas, | |
// but tries to maintain the targetRatio (above). | |
if ((window.innerWidth / window.innerHeight) > TARGET_RATIO) { | |
// window is too wide | |
canvas.height = window.innerHeight; | |
canvas.width = canvas.height * TARGET_RATIO; | |
canvas.style.top = "0px"; | |
canvas.style.left = ((window.innerWidth - canvas.width) / 2) + "px"; | |
} else { | |
canvas.width = window.innerWidth; | |
canvas.height = canvas.width / TARGET_RATIO; | |
canvas.style.top = ((window.innerHeight - canvas.height) / 2) + "px"; | |
canvas.style.left = "0px"; | |
} | |
// This next block zooms the canvas, | |
// so keep all your draw calls inside VIEWPORT_X or Y and it should Just Work. | |
// Note that changing canvas.width or canvas.height also | |
// * clears the canvas, and * resets the transformation matrix. | |
var zoom = canvas.height / VIEWPORT_Y; | |
context.scale(zoom,zoom); | |
} | |
//////////////////////// | |
// INITIALIZATION | |
window.addEventListener("resize",resizeCanvas); | |
resizeCanvas(); |
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