截屏与图片的截屏

• 布局图:
  

• 主要代码:

// ViewController.h
#import <UIKit/UIKit.h>

@interface ViewController : UIViewController


@end

// ViewController.m
#import "ViewController.h"

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIImageView *imageV;

@property (nonatomic, assign)CGPoint startP;

@property (nonatomic, weak) UIView *coverView;

@end

@implementation ViewController

// 懒加载:1.什么时候用到什么时候才去创建
//      2.保持当前的View在内存当中只有一份.
//      3.保持用到View时,肯定是有值的.
-(UIView *)coverView {

    if (_coverView == nil) {
        //创建UIView
        UIView *coverView = [[UIView alloc] init];
        coverView.backgroundColor = [UIColor blackColor];
        coverView.alpha = 0.7;
        _coverView = coverView;
        [self.view addSubview:coverView];
    }
    return _coverView;

}

- (IBAction)pan:(UIPanGestureRecognizer *)pan {

    //获取当前手指所在的点
    CGPoint curP = [pan locationInView:self.imageV];
    //判断手势的状态
    if(pan.state == UIGestureRecognizerStateBegan) {
        //记录当前手指的开始点
        self.startP = curP;

    } else if(pan.state == UIGestureRecognizerStateChanged) {

        //rect
        CGFloat w = curP.x - self.startP.x;
        CGFloat h = curP.y - self.startP.y;
        CGRect rect = CGRectMake(self.startP.x, self.startP.y, w, h);

        self.coverView.frame = rect;

    } else if(pan.state == UIGestureRecognizerStateEnded) {


        // 生成一张图片
        // 1.开启位图上下文
        UIGraphicsBeginImageContext(self.imageV.bounds.size);

        // 2.设置裁剪区域
        UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.coverView.frame];
        [path addClip];

        // 3.把UIImageV当中的内容渲染到上下文当中
        // 拿到当前上下文
        CGContextRef ctx = UIGraphicsGetCurrentContext();
        [self.imageV.layer renderInContext:ctx];

        // 4.从上下文当中获取图片
        UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

        // 5.关闭上下文
        UIGraphicsEndImageContext();

        self.imageV.image = newImage;

        [self.coverView removeFromSuperview];
    }

}



- (void)viewDidLoad {
    [super viewDidLoad];
}


-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    // 截屏
//    [self screenCapture];
}

// 截屏
- (void)screenCapture {
    // 生成图片
    // 1.开启一个位图上下文
    UIGraphicsBeginImageContext(self.view.bounds.size);
    // 拿到当前上下文,即当前位图上下文
    CGContextRef ctx =  UIGraphicsGetCurrentContext();
    // 2.把View的内容绘制到上下文当中
    // UIView内容想要绘制到上下文当中, 必须使用渲染的方式
    [self.view.layer renderInContext:ctx];
    // 3.从上下文当中生成一张图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    // 4.关闭上下文
    UIGraphicsEndImageContext();
    // 把图片转成二进制流
    // NSData *data = UIImageJPEGRepresentation(newImage, 1); // 1代表不压缩
    NSData *data = UIImagePNGRepresentation(newImage);

    [data writeToFile:@"/Users/apple/Desktop/newImage.png" atomically:YES];
}

@end

• 赠送一个福利

// UIImage+Image.h
#import <UIKit/UIKit.h>

@interface UIImage (Image)


// 根据颜色生成一张尺寸为1*1的相同颜色图片
+ (UIImage *)imageWithColor:(UIColor *)color;


@end

// UIImage+Image.m
#import "UIImage+Image.h"

@implementation UIImage (Image)

+ (UIImage *)imageWithColor:(UIColor *)color {
    // 描述矩形
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);

    // 开启位图上下文
    UIGraphicsBeginImageContext(rect.size);
    // 获取位图上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    // 使用color演示填充上下文
    CGContextSetFillColorWithColor(context, [color CGColor]);
    // 渲染上下文
    CGContextFillRect(context, rect);
    // 从上下文中获取图片
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    // 结束上下文
    UIGraphicsEndImageContext();

    return theImage;
}


@end

• 效果: