JavaScript - canvas - 放大镜

效果

示例

项目结构:

源码:

html 复制代码
<!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 image
                const 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";
                
                // Hovered
                canvas.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-aliasing
                        canvasPieceContext.drawImage(canvas, (x - 50), (y - 50), 100, 100, 0, 0, (100 * 2), (100 * 2));
                    }
                }
            }
        </script>
    </body>
</html>
相关推荐
dy17173 小时前
element-plus表格默认展开有子的数据
前端·javascript·vue.js
一朵梨花压海棠go8 小时前
html+js实现表格本地筛选
开发语言·javascript·html·ecmascript
一只小风华~9 小时前
Vue: Class 与 Style 绑定
前端·javascript·vue.js·typescript·前端框架
十碗饭吃不饱9 小时前
net::ERR_EMPTY_RESPONSE
java·javascript·chrome·html5
Zz_waiting.10 小时前
Javaweb - 14.6 - Vue3 数据交互 Axios
开发语言·前端·javascript·vue·axios
每天吃饭的羊11 小时前
state和ref
前端·javascript·react.js
GEO_YScsn11 小时前
Vite:Next-Gen Frontend Tooling 的高效之道——从原理到实践的性能革命
前端·javascript·css·tensorflow
GISer_Jing11 小时前
滴滴二面(准备二)
前端·javascript·vue·reactjs
摇滚侠11 小时前
Vue3入门到实战,最新版vue3+TypeScript前端开发教程,笔记03
javascript·笔记·typescript
GISer_Jing11 小时前
滴滴二面准备(一)
前端·javascript·面试·ecmascript