图片格式

#pragma mark 图片格式
+ (NSString *)typeForImageData:(NSData *)data {
    
    
    uint8_t c;
    
    [data getBytes:&c length:1];
    
    
    
    switch (c) {
            
        case 0xFF:
            
            return @"image/jpeg";
            
        case 0x89:
            
            return @"image/png";
            
        case 0x47:
            
            return @"image/gif";
            
        case 0x49:
            
        case 0x4D:
            
            return @"image/tiff";
            
    }
    
    return nil;
    
}