1. 什么是大端和小端？

• 大端模式：高位字節(jié)排放在內(nèi)存的低地址端，低位字節(jié)排放在內(nèi)存的高地址段。
• 小端模式：低位字節(jié)排放在內(nèi)存的低地址端，高位字節(jié)排放在內(nèi)存的高地址端。

2. 一個NSObject對象占用多少內(nèi)存

• 系統(tǒng)分配了16個字節(jié)給NSObject對象（通過malloc_size函數(shù)獲得）
• 但NSObject對象內(nèi)部只使用了8個字節(jié)的空間（64bit環(huán)境下）

 NSObject *obj = [[NSObject alloc] init];
 NSLog(@"%zd", class_getInstanceSize([NSObject class]));
 NSLog(@"%zd", malloc_size((__bridge void *)obj));

3. ImageIO學習

- (void)viewDidLoad {
    [super viewDidLoad];

    
    UIImageView *iv = [[UIImageView alloc] initWithFrame:CGRectMake(60, 120, [UIScreen mainScreen].bounds.size.width - 120, 160)];
    [self.view addSubview:iv];
    
//
//    UIImage *image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"11.jpeg" ofType:nil]];
//    NSData *data = UIImageJPEGRepresentation(image, 1.0);
//    SDImageFormat type = [NSData sd_imageFormatForImageData:data];
//    NSLog(@"%zd", type);
//
//    NSString *typeStr = (NSString *)[NSData sd_UTTypeFromImageFormat:type];
//    NSLog(@"%@", typeStr);
    
//    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);

    NSString *path = [[NSBundle mainBundle] pathForResource:@"show.gif" ofType:nil];
    NSURL *url = [NSURL fileURLWithPath:path];

    CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)url, NULL);

    long count = CGImageSourceGetCount(source);
    NSLog(@"圖片個數(shù)%ld", count);
    //獲取第幾張圖片
    CGImageRef firstImage = CGImageSourceCreateImageAtIndex(source, 23, NULL);

    NSArray *arr = CFBridgingRelease(CGImageSourceCopyTypeIdentifiers());
    NSLog(@"支持的類型\n%@", arr);

    NSString *type = CFBridgingRelease(CGImageSourceGetType(source));
    NSLog(@"所加載圖片的類型為：%@", type);

    // 獲取某一幀圖片的縮略圖
    CGImageRef thumbnailImage = CGImageSourceCreateThumbnailAtIndex(source, 0, NULL);
    NSLog(@"%@", thumbnailImage);
    
    CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(source, 0, NULL);
    
    NSInteger orientationValue = 1;
    CFTypeRef val = CFDictionaryGetValue(properties, kCGImagePropertyPixelHeight);
    // 圖片的高度
    if (val) CFNumberGetValue(val, kCFNumberLongType, &_height);
    val = CFDictionaryGetValue(properties, kCGImagePropertyPixelWidth);
    // 圖片的寬度
    if (val) CFNumberGetValue(val, kCFNumberLongType, &_width);
    val = CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
    // 圖片的方向
    if (val) CFNumberGetValue(val, kCFNumberNSIntegerType, &orientationValue);
    
    CFRelease(source);
    _orientation = (CGImagePropertyOrientation)orientationValue;
    
    
    iv.image = [UIImage imageWithCGImage:thumbnailImage];
}