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March 11, 2018 19:49
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A simple canvas animation...
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| license: gpl-3.0 | |
| height: 500 |
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> | |
| <meta http-equiv="X-UA-Compatible" content="ie=edge"> | |
| <title></title> | |
| </head> | |
| <body> | |
| <canvas id="myCanvas" width="500px" height="500px"></canvas> | |
| <script> | |
| getRandomInt = (min, max) => { | |
| return Math.floor(Math.random() * (max - min + 1)) + min; | |
| } | |
| drawPoint = () => { | |
| ctx.fillStyle = '#b2182b' | |
| ctx.beginPath() | |
| ctx.arc(init.x, init.y, 5, 0, 2 * Math.PI) | |
| ctx.fill() | |
| } | |
| canvas = document.getElementById("myCanvas") | |
| ctx = canvas.getContext("2d") | |
| const width = canvas.width | |
| const height = canvas.height | |
| ctx.strokeRect(0, 0, width, height); | |
| const init = { x: width / 2, y: height / 2 } | |
| const anim = setInterval(() => { | |
| // Clear the canvas | |
| ctx.clearRect(0, 0, width, height) | |
| // Fill in the canvas in grey | |
| ctx.fillStyle = '#4d4d4d' | |
| ctx.fillRect(0, 0, width, height); | |
| // Draw a white circle that contains the point | |
| const radius = Math.sqrt(Math.abs(init.x - width / 2) ** 2 + Math.abs(init.y - height / 2) ** 2) + 5 | |
| ctx.beginPath() | |
| ctx.arc(width / 2, height / 2, radius, 0, 2 * Math.PI) | |
| ctx.fillStyle = 'white' | |
| ctx.fill() | |
| // Draw the point | |
| drawPoint() | |
| // Update the center of the point | |
| init.x += getRandomInt(-5, 5) | |
| init.y += getRandomInt(-5, 5) | |
| // Stop the animation if the point touches an edge of the canvas | |
| if (init.x <= 0 || init.x >= width || init.y <= 0 || init.y >= height) { | |
| clearInterval(anim) | |
| } | |
| }, 80) | |
| </script> | |
| </body> | |
| </html> |
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