iOS 部分API理解

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UIImageView *imageView = [[UIImageView alloc]initWithImage:[[UIImage imageNamed:@"AppIconImage"] imageWithRenderingMode:UIImageRenderingModeAutomatic]];   //根据图片所在的位置不同来自动选择渲染模式
    
    UIImageView *imageView1 = [[UIImageView alloc]initWithImage:[[UIImage imageNamed:@"AppIconImage"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]];  //默认采用图片的原始颜色来进行图片渲染
    imageView1.frame = CGRectMake(0, 50, imageView1.frame.size.width, imageView1.size.height);
    
    UIImageView *imageView2 = [[UIImageView alloc]initWithImage:[[UIImage imageNamed:@"AppIconImage"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate]];  //采用蓝色作为渲染颜色，忽略原始图片的颜色
    imageView2.frame = CGRectMake(0, 150, imageView1.frame.size.width, imageView1.size.height);
    
    [self.view addSubview:imageView];
    [self.view addSubview:imageView1];
    [self.view addSubview:imageView2];
    
}

//以下三个函数都用来处理绝对值的。只不过处理的类型不一样。

int abs(int i);                   // 处理int类型的取绝对值
double fabs(double i); //处理double类型的取绝对值
float fabsf(float i);           //处理float类型的取绝对值