【代码笔记】iOS-根据size截取屏幕中间矩形区域

#import "RootViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    if (self) {

        // Custom initialization

    }

    return self;

}

- (void)viewDidLoad

{

    [super viewDidLoad];

    // Do any additional setup after loading the view.

    //初始化界面

    [self addView];

}

#pragma -mark -functions

//初始化界面

-(void)addView

{

    UIImageView *imageView=[[UIImageView alloc]initWithFrame:CGRectMake(50, 100, 200, 200)];

    imageView.backgroundColor=[UIColor redColor];

    //显示截取的图

    imageView.image=[self cutCenterImage:[UIImage imageNamed:@"1.jpg"] size:CGSizeMake(200, 200)];

    [self.view addSubview:imageView];

}

#pragma mark 根据size截取图片中间矩形区域的图片 这里的size是正方形

-(UIImage *)cutCenterImage:(UIImage *)image size:(CGSize)size{

    CGSize imageSize = image.size;

    CGRect rect;

    //根据图片的大小计算出图片中间矩形区域的位置与大小

    if (imageSize.width > imageSize.height) {

        float leftMargin = (imageSize.width - imageSize.height) * 0.5;

        rect = CGRectMake(leftMargin, 0, imageSize.height, imageSize.height);

    }else{

        float topMargin = (imageSize.height - imageSize.width) * 0.5;

        rect = CGRectMake(0, topMargin, imageSize.width, imageSize.width);

    }

    CGImageRef imageRef = image.CGImage;

    //截取中间区域矩形图片

    CGImageRef imageRefRect = CGImageCreateWithImageInRect(imageRef, rect);

    UIImage *tmp = [[UIImage alloc] initWithCGImage:imageRefRect];

    CGImageRelease(imageRefRect);

    UIGraphicsBeginImageContext(size);

    CGRect rectDraw = CGRectMake(0, 0, size.width, size.height);

    [tmp drawInRect:rectDraw];

    // 从当前context中创建一个改变大小后的图片

    tmp = UIGraphicsGetImageFromCurrentImageContext();

    // 使当前的context出堆栈

    UIGraphicsEndImageContext();

    return tmp;

}

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}