js file取得图片大小

function getImageSize(url) {
    return new Promise((resolve, reject) => {
        const img = new Image();
        img.onload = () => resolve({ width: img.width, height: img.height });
        img.onerror = reject;
        img.src = url;
    });
}

// 使用示例
getImageSize('path/to/image.jpg')
    .then(size => console.log('Image size:', size))
    .catch(error => console.error('Error loading image:', error));

function getImageSizeFromFile(file) {
    return new Promise((resolve, reject) => {
        const reader = new FileReader();
        reader.onload = (event) => {
            const img = new Image();
            img.onload = () => resolve({ width: img.width, height: img.height });
            img.onerror = reject;
            img.src = event.target.result;
        };
        reader.onerror = reject;
        reader.readAsDataURL(file);
    });
}

// 使用示例
const fileInput = document.querySelector('input[type="file"]');
fileInput.addEventListener('change', (event) => {
    const file = event.target.files[0];
    getImageSizeFromFile(file)
        .then(size => console.log('Image size:', size))
        .catch(error => console.error('Error loading image:', error));
});

function getFileSize(url) {
    return new Promise((resolve, reject) => {
        const xhr = new XMLHttpRequest();
        xhr.open('HEAD', url, true);
        xhr.onreadystatechange = function() {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    resolve(parseInt(xhr.getResponseHeader('content-length'), 10));
                } else {
                    reject(new Error('Could not get file size'));
                }
            }
        };
        xhr.send(null);
    });
}

// 使用示例
getFileSize('path/to/image.jpg')
    .then(size => console.log('File size:', size))
    .catch(error => console.error('Error getting file size:', error));