canvas火焰按钮动画

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html

css

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html

css

body {
  display: flex;
  align-items: center;
  justify-content: center;
  position: fixed;
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  background-color: #131313;
  font-family: 'Press Start 2P', cursive;
}
#button {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  top: -5px;
  left: -5px;
  overflow: hidden;
  width: 240px;
  height: 60px;
  padding: 0;
  border: 2px solid #fff;
  background-color: #000;
  box-shadow: 5px 5px 0 #fff;
  cursor: pointer;
  outline: none;
  -webkit-appearance: none;
     -moz-appearance: none;
          appearance: none;
  transition: all 0.15s ease-in-out;
}
#button:active {
  top: 0;
  left: 0;
  box-shadow: none;
}
#button:hover {
  opacity: 0.9;
}
span {
  display: block;
  position: relative;
  color: #fff;
  font-family: 'Press Start 2P', cursive;
  font-size: 18px;
  font-weight: bold;
  text-shadow: 1px 2px 0 rgba(0,0,0,0.8);
  z-index: 1;
}
canvas {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
}

JavaScript

const MAX_COLORS = 768;
const CHUNK = 3;
const GUTTER_LINES = 5;

function getColors() {

const setColor = (colorArray, colorIndex, r, g, b) => {
    const baseIndex = colorIndex << 2;
    colorArray[baseIndex] = r;
    colorArray[baseIndex + 1] = g;
    colorArray[baseIndex + 2] = b;
    colorArray[baseIndex + 3] = 0xff;
  };

const colors = new Uint8ClampedArray(256 * 3 * 4);
  for (let i = 0; i < 256; i++) {
    setColor(colors, i, i, 0, 0);
    setColor(colors, i + 256, 0xff, i, 0);
    setColor(colors, i + 512, 0xff, 0xff, i);
  }

return colors;
}

function flipBuffers() {
  mainBuffer = 1 - mainBuffer;
  backBuffer = 1 - backBuffer;
}

function loop() {

if (isGenerate) {
    for (let n = 0; n < canvas.width / CHUNK; n++) {
      const color = Math.random() >= 0.4 ? MAX_COLORS - 1 : 0;
      for (let c = 0; c < CHUNK; c++) {
        buffers[backBuffer][numPixels - n * CHUNK - c] = color;
      }
    }
  }

for (let y = canvas.height - 1; y >= 1; y--) {
    for (let x = 1; x < canvas.width - 1; x++) {
      let sum = 0;
      const pixelIndex = y * canvas.width + x;
      sum += buffers[backBuffer][pixelIndex];
      sum += buffers[backBuffer][pixelIndex + canvas.width - 1];
      sum += buffers[backBuffer][pixelIndex + canvas.width];
      sum += buffers[backBuffer][pixelIndex + canvas.width + 1];
      sum /= 4;
      sum -= (1.0 - y / canvas.height) * 10.0;

if (sum < 0) sum = 0;
      if (sum >= MAX_COLORS) sum = MAX_COLORS - 1;

buffers[mainBuffer][pixelIndex] = sum;
    }
  }

const skippedPixels = GUTTER_LINES * canvas.width;
  for (let i = 0; i < numPixels - skippedPixels; i++) {
    const baseTargetIndex = skippedPixels + i << 2;
    const baseSourceIndex = buffers[mainBuffer][i] << 2;
    fireImage.data[baseTargetIndex] = colors[baseSourceIndex];
    fireImage.data[baseTargetIndex + 1] = colors[baseSourceIndex + 1];
    fireImage.data[baseTargetIndex + 2] = colors[baseSourceIndex + 2];
    fireImage.data[baseTargetIndex + 3] = colors[baseSourceIndex + 3];
  }

context.putImageData(fireImage, 0, 0);
  flipBuffers();
  window.requestAnimationFrame(loop);

}

const button = document.getElementById("button");
const canvas = document.getElementById("canvas");

canvas.width = button.clientWidth;
canvas.height = button.clientHeight;

const colors = getColors();
const context = canvas.getContext("2d");
const fireImage = context.createImageData(canvas.width, canvas.height);
const numPixels = fireImage.width * fireImage.height;
const buffers = [new Uint16Array(numPixels), new Uint16Array(numPixels)];

let mainBuffer = 0;
let backBuffer = 1;
let isGenerate = true;

button.addEventListener('click', () => {
  isGenerate = !isGenerate;
});
window.requestAnimationFrame(loop);

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