Get the image type from a buffer

getImageType.ts

/**
 * Get the type of an image.
 * @param image The image as a buffer.
 * @returns The type of the image.
 */
export function getImageType(image: Buffer): Promise<{ mimeType: string, extension: string }> {
    return new Promise((resolve, reject) => {
        if (image[0] === 0xFF && image[1] === 0xD8 && image[2] === 0xFF) {
            resolve({
                mimeType: 'image/jpeg',
                extension: 'jpg',
            });
        }
        else if (image[0] === 0x89 && image[1] === 0x50 && image[2] === 0x4E && image[3] === 0x47) {
            resolve({
                mimeType: 'image/png',
                extension: 'png',
            });
        }
        else if (image[0] === 0x47 && image[1] === 0x49 && image[2] === 0x46 && image[3] === 0x38) {
            resolve({
                mimeType: 'image/gif',
                extension: 'gif',
            });
        }
        else if (image[0] === 0x42 && image[1] === 0x4D) {
            resolve({
                mimeType: 'image/bmp',
                extension: 'bmp',
            });
        }
        else if (image[0] === 0x52 && image[1] === 0x49 && image[2] === 0x46 && image[3] === 0x46 && image[8] === 0x57 && image[9] === 0x45 && image[10] === 0x42 && image[11] === 0x50) {
            resolve({
                mimeType: 'image/webp',
                extension: 'webp',
            });
        }
        else {
            reject(Error('Unsupported image type.'));
        }
    });
}