js 图片 缩放

function scaleImage(imgUrl, scale) {
    return new Promise((resolve, reject) => {
        const img = new Image();
        img.crossOrigin = "Anonymous"; // 如果图片跨域需要设置
        img.onload = () => {
            const canvas = document.createElement('canvas');
            const ctx = canvas.getContext('2d');
            const newWidth = img.width * scale;
            const newHeight = img.height * scale;
            canvas.width = newWidth;
            canvas.height = newHeight;
            ctx.drawImage(img, 0, 0, newWidth, newHeight);
            canvas.toBlob((blob) => {
                if (blob) {
                    resolve(URL.createObjectURL(blob));
                } else {
                    reject(new Error('图片缩放失败'));
                }
            }, 'image/jpeg');
        };
        img.onerror = () => reject(new Error('图片加载失败'));
        img.src = imgUrl;
    });
}

// 使用示例
scaleImage('path/to/image.jpg', 0.5).then(scaledImageUrl => {
    // 使用缩放后的图片URL
}).catch(error => {
    console.error(error);
});