H5 Canvas 举牌小人

news2024/11/23 10:19:38

之前看到这种的举牌小人的图片觉得很有意思，最近有时间所以就尝试写写看。

在线链接
https://linyisonger.github.io/H5.Examples/?name=./080.Canvas%20%E4%B8%BE%E7%89%8C%E5%B0%8F%E4%BA%BA.html
生成效果
请添加图片描述
实现代码

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="./assets/global.css">

    <style>
        .content {
            display: flex;
        }

        .content textarea {
            width: 300px;
            resize: none;
            border-radius: 0;
            outline: none;
            border-right-width: 0;
        }

        .content .save-btn {
            padding: 10px;
            background-color: #eefdfd;
            font-size: 15px;
            cursor: pointer;
            user-select: none;
            border-color: rgb(133, 133, 133);
            border-width: 1px; 
        }

        .content .save-btn:disabled {
            background-color: #b3b3b3;
        }
    </style>
</head>

<body>
    <div class="content">
        <textarea rows="2" placeholder="请输入需要生成的举牌文字"></textarea>

        <button class="save-btn" disabled>保存图片</button>
    </div>

    <canvas id="preview"></canvas>


    <script type="module">
        import { Randoms } from "https://gcore.jsdelivr.net/npm/@3r/tool/lib/randoms.js";

        /** @type {HTMLCanvasElement} */
        let canvas = document.querySelector("#preview")
        let ctx = canvas.getContext('2d')


        /**
         * 随机人物
         */
        function randomPerson() {
            let length = 41;
            let width = 80;
            let height = 165
            let index = Randoms.int(0, length)
            return {
                sx: index * width,
                sy: 0,
                sw: width,
                sh: height,
            }
        }

        /**
         * 绘制字符
         */
        function drawChar(char, x, y, w, h) {
            let charCenterX = x + 38
            let charCenterY = y + 28
            ctx.drawImage(image, ...Object.values(randomPerson()), x, y, w, h)
            ctx.font = '18px Helvetica'
            ctx.textAlign = "center"
            ctx.textBaseline = "middle"
            ctx.save();
            ctx.translate(charCenterX, charCenterY);
            ctx.rotate(Math.PI / 6);
            ctx.fillText(char, 0, 0)
            ctx.restore();
        }

        /**
         * 渲染文字
         * 1.分行决定渲染图片大小
         * 2.逐行偏移
         */
        function drawText(text) {
            ctx.clearRect(0, 0, canvas.width, canvas.height)

            let rows = text.split('\n')
            // 预处理
            let drawCharParams = []
            let maxX = 0;
            let maxY = 0;
            let width = 80;
            let height = 165;
            for (let i = 0; i < rows.length; i++) {
                let cols = rows[i].split('')
                let offsetX = (rows.length - i - 1) * (width / 2)
                let offsetY = i * (width / 2);
                for (let j = 0; j < cols.length; j++) {
                    const char = cols[j];
                    if (char === ' ') continue // 空字符跳过 
                    let x = j * 40 + offsetX;
                    let y = j * 15 + offsetY;
                    maxX = Math.max(maxX, x)
                    maxY = Math.max(maxY, y)
                    drawCharParams.push([char, x, y, width, height])
                }
            }
            // 更新画布大小
            canvas.setAttribute('style', `width:${maxX + width}px;height:${maxY + height}px`)
            canvas.width = canvas.clientWidth;
            canvas.height = canvas.clientHeight;
            // 处理
            for (let i = 0; i < drawCharParams.length; i++) {
                drawChar(...drawCharParams[i])
            }

        }


        let image = new Image()
        image.src = './assets/upup.png'

        let textareaDom = document.querySelector(".content textarea")
        textareaDom.addEventListener('change', (e) => {
            let text = e.target.value
            drawText(text)
        })

        let saveBtnDom = document.querySelector('.save-btn')
        saveBtnDom.addEventListener('click', (e) => {
            let a = document.createElement('a');
            a.href = window.URL.createObjectURL(base64ToBlob(canvas.toDataURL("image/png", 0.8)));
            a.setAttribute('download', '举牌小人.png');
            a.click();
        })

        image.onload = () => {
            saveBtnDom.disabled = false
        }
        // base64 转 Blob
        function base64ToBlob(base64) {
            let arr = base64.split(',');
            let mime = arr[0].match(/:(.*?);/)[1];
            let bstr = atob(arr[1]);
            let n = bstr.length;
            let u8arr = new Uint8Array(n);
            while (n--) {
                u8arr[n] = bstr.charCodeAt(n);
            }
            return new Blob([u8arr], { type: mime })
        }
    </script>
</body>

</html>