JavaScript - canvas

JavaScript - canvas - 放大镜

效果

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示例

项目结构：

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源码：

<!DOCTYPE html>
<html><head><meta charset="utf-8" /><title>放大镜</title><style type="text/css">div {width: 200px;height: 200px;display: inline-block;}</style></head><body><canvas id="canvas"></canvas><canvas id="piece" width="200" height="200" style="border: 1px solid black;"></canvas><script type="text/javascript">window.onload = (event) => {// console.log(event);main();}function main() {const canvas = document.querySelector("#canvas");const canvasContext = canvas.getContext("2d");const canvasPiece = document.querySelector("#piece");const canvasPieceContext = canvasPiece.getContext("2d");// canvasPieceContext.imageSmoothingEnabled = false;// Load imageconst image = new Image();image.onload = (event) => {// console.log(event);canvas.width = image.width;canvas.height = image.height;canvasContext.drawImage(image, 0, 0);}image.src = "img/transformers.jpg";// Hoveredcanvas.onmousemove = (event) => {// console.log(event);const x = event.layerX;const y = event.layerY;// 两倍放大{// https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage// drawImage(image, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight)// https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas#zooming_and_anti-aliasingcanvasPieceContext.drawImage(canvas, (x - 50), (y - 50), 100, 100, 0, 0, (100 * 2), (100 * 2));}}}</script></body>
</html>