site-z/canvas2.html at master · LFF5644/site-z · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
	<?=globals.functions.importHead({
		input,
		tabs:1,
		title: "canvas draw line",
	})?>
</head>
<body>
	<h1>Ich bin Canvas</h1>
	<canvas id="meinCanvas" width=300 height=100 style="border:1px solid #000000;"></canvas>
	<p><button onclick="render()">render</button></p>
	<p id=p_data>press render button</p>
	<script>
		function render(){
			const canvas = document.getElementById("meinCanvas");
			const {height,width}=canvas;
			const ctx = canvas.getContext("2d");
			ctx.clearRect(0,0,width,height);

			const data=[];
			for(let counter=0; counter<width/4; counter+=1){
				data.push(Math.round(Math.min(Math.random()*height,height)));
			}

			ctx.beginPath();
			ctx.moveTo(0,height);

			let multiplayer=width/data.length;
			if(multiplayer<1) multiplayer=1;
			for(let index=0; index<data.length; index+=1){
				const width_offset=Math.round(index*multiplayer);
				const y=data[index];
				if(width_offset>width) break;
				ctx.lineTo(width_offset,y);
				//console.log("Y X",width_offset,y);
			}
			ctx.stroke();         // Linie zeichnen

			// Linie von x=10,y=10 nach x=200,y=100
			//ctx.beginPath();
			//ctx.moveTo(0,0); // Startpunkt
			//ctx.lineTo(width,height); // Endpunkt
			//ctx.stroke(); // Linie zeichnen
		}
		render();
	</script>

</body>
</html>