tianyunperfect
/
web-base--


			
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							<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>webp</title>
    <style>
        #image-display {
            max-width: 100%;
            max-height: 100%;
            border: 1px solid gray;
        }
    </style>
</head>
<body>
<h1>粘贴图片并展示</h1>
<p>右键粘贴图片，本地图片或网络图片地址都可以，将被压缩为webp格式并展示，压缩前：<span id="preSize"></span>, 压缩后：<span id="afterSize"></span><span id="status"></span>&nbsp;。&nbsp;
    <button onclick="rotateImage()">旋转90度</button> &nbsp;。&nbsp;
<!--    <button onclick="bigImage()">放大</button> &nbsp;。&nbsp;-->
<!--    <button onclick="smallImage()">缩小</button> &nbsp;。&nbsp;-->
</p>
<div id="image-container">
    <img id="image-display" src="" alt="Image Display">
</div>
<script>
    const imageDisplay = document.getElementById("image-display");

    function formatSize(sizeInBytes) {
        const sizeInKb = sizeInBytes / 1024;
        const sizeInMb = sizeInBytes / 1048576;
        if (sizeInMb >= 1) {
            return `${sizeInMb.toFixed(2)} MB`;
        } else {
            return `${sizeInKb.toFixed(2)} KB`;
        }
    }

    // 监听粘贴事件
    document.addEventListener("paste", (event) => {
        handleClipboardItems(event.clipboardData.items);
    });

    // 监听拖拽事件
    document.addEventListener("dragover", (event) => {
        event.preventDefault();
    });

    document.addEventListener("drop", (event) => {
        event.preventDefault();
        handleClipboardItems(event.dataTransfer.items);
    });


    function compressImageToSize(blobFile, targetSize = 300 * 1024, maxIterations = 5, minQuality = 0.01) {
        let currentQuality = 0.8; // 初始压缩质量
        let iteration = 0; // 当前迭代次数
        function compressImage(blobFile, quality = 0.8) {
            // 返回一个Promise对象
            return new Promise((resolve, reject) => {
                // 创建一个Image对象
                const image = new Image();
                // 当Image对象加载完成时，执行以下操作
                image.onload = () => {
                    const canvas = document.createElement("canvas");
                    canvas.width = image.naturalWidth;
                    canvas.height = image.naturalHeight;
                    const context = canvas.getContext("2d");
                    context.drawImage(image, 0, 0);
                    canvas.toBlob((webpBlob) => {
                        // 解决Promise，并传递压缩后的Blob对象
                        resolve(webpBlob);
                    }, "image/webp", quality);
                    // 如果在转换过程中发生错误，拒绝Promise
                };
                image.src = URL.createObjectURL(blobFile);
            });
        }

        function attemptCompression() {
            return new Promise((resolve, reject) => {
                // 递归调用compressImage函数进行压缩
                compressImage(blobFile, currentQuality).then(compressedBlob => {
                    // 检查压缩后的文件大小是否满足条件
                    if (compressedBlob.size <= targetSize) {
                        // 如果压缩后的文件大小小于或等于目标大小，则解决Promise
                        resolve(compressedBlob);
                    } else if (iteration < maxIterations && currentQuality > minQuality) {
                        // 如果还未达到最大迭代次数且质量还可以降低，则递减质量并再次尝试压缩
                        currentQuality *= 0.8; // 每次迭代降低质量的百分比
                        blobFile = compressedBlob; // 使用上一次压缩的结果作为下一次的输入
                        iteration++; // 增加迭代次数
                        attemptCompression().then(resolve).catch(reject);
                    } else {
                        // 如果已经达到最大迭代次数或者质量已经很低，拒绝Promise
                        reject(new Error("Unable to compress the image to the target size."));
                    }
                }).catch(reject);
            });
        }

        // 启动压缩过程
        return new Promise((resolve, reject) => {
            attemptCompression().then(resolve).catch(reject);
        });
    }

    // 处理粘贴板或拖拽项
    function handleClipboardItems(items) {
        if (!items) {
            return;
        }
        // 查找图片数据
        for (let i = 0; i < items.length; i++) {
            if (items[i].type.indexOf("image") !== -1) {
                document.getElementById("preSize").innerText = "";
                document.getElementById("afterSize").innerText = "";
                // 获取图片文件或URL
                const blobFile = items[i].getAsFile();

                // 将图片展示
                document.getElementById("status").innerText = " 压缩中……";
                document.getElementById("preSize").innerText = formatSize(blobFile.size);

                // 压缩为webp格式
                compressImageToSize(blobFile).then(webpBlob => {
                    // 将压缩后的webp图片展示在页面上
                    // imageDisplay.src = URL.createObjectURL(webpBlob);
                    const reader = new FileReader();
                    reader.onloadend = () => {imageDisplay.src = reader.result;};
                    reader.readAsDataURL(webpBlob);
                    showSize(webpBlob);
                });


                // 防止页面跳转
                event.preventDefault();
                break
            }
        }
    }

    function showSize(webpBlob) {
        document.getElementById("status").innerText = " 已压缩 ☺";
        document.getElementById("afterSize").innerText = formatSize(webpBlob.size);
    }

    // 选择90度旋转
    function rotateImage() {
        const image = document.getElementById("image-display");
        const canvas = document.createElement("canvas");
        const context = canvas.getContext("2d");

        // 旋转90度
        canvas.width = image.height;
        canvas.height = image.width;
        context.rotate(90 * Math.PI / 180);
        context.drawImage(image, 0, -canvas.width);

        // 将旋转后的图片展示在页面上
        const rotatedImageUrl = canvas.toDataURL();
        image.src = rotatedImageUrl;
    }


</script>
</body>
</html>