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
爱学习的茄子1 小时前
JavaScript事件循环深度解析:理解异步执行的本质
前端·javascript·面试
1024小神1 小时前
cocos游戏开发中多角色碰撞,物理反弹后改变方向的实现逻辑
前端·javascript
ruanhongbiao1 小时前
饿了么el-upload上传组件报错:TypeError: ***.upload.addEventListener is not a function
javascript·elementui
_一两风1 小时前
JS执行机制-event loop
javascript
止观止1 小时前
JavaScript对象创建9大核心技术解析
开发语言·javascript·ecmascript
1024小神1 小时前
cocos游戏开发中,如何制作一个空气墙
前端·javascript
爱编程的喵1 小时前
深入理解JavaScript事件循环机制:从同步到异步的完整解析
前端·javascript
20261 小时前
11. vite打包优化
前端·javascript·vite
1024小神2 小时前
Cocos游戏开发中,检测两个物体碰撞,并实现物理反弹逻辑
前端·javascript
一一一8712 小时前
javaScript数据存储, 对象和原型与原型链
javascript