（IOS）截图Demo

思路是建一个UIView的子类，获取划动出的矩形，用协议将矩形传递给代理对象，依据该矩形完成图像数据的截取，并显示出来。

截图视图类：

#import <UIKit/UIKit.h>@protocol UICutImgDelegate;@interface BIDCutView : UIView
{CGPoint startPoint;CGRect targetRect;id <UICutImgDelegate> _delegate;
}
@property (assign , nonatomic) id delegate;
@end@protocol UICutImgDelegate <NSObject>
-(void)cutImgWithRect:(CGRect) aRect;
-(void)clear;
@end

#import "BIDCutView.h"@implementation BIDCutView@synthesize delegate=_delegate;- (id)initWithFrame:(CGRect)frame
{self = [super initWithFrame:frame];if (self) {// Initialization code
    }return self;
}- (void)drawRect:(CGRect)rect
{CGContextRef ctx = UIGraphicsGetCurrentContext();CGContextSetLineWidth(ctx, 1.5);CGContextSetStrokeColorWithColor(ctx, [UIColor purpleColor].CGColor);CGFloat lengths[2] = {15.0,5.0};CGContextSetLineDash(ctx, 2, lengths, 2);CGContextStrokeRect(ctx, targetRect);  //画虚线矩形
}-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{[self.delegate clear];startPoint=[[touches anyObject] locationInView:self];
}-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{CGPoint currentPoint=[[touches anyObject] locationInView:self];targetRect = CGRectMake(startPoint.x, startPoint.y, currentPoint.x-startPoint.x, currentPoint.y-startPoint.y);[self setNeedsDisplay];
}-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{if (self.delegate && [self.delegate respondsToSelector:@selector(cutImgWithRect:)]) {[self.delegate cutImgWithRect:targetRect];}
}
@end

视图控制器：（作为截图视图的代理对象）

#import <UIKit/UIKit.h>
#import "BIDCutView.h"@interface BIDRootViewController : UIViewController <UICutImgDelegate>@end

#import "BIDRootViewController.h"
#import "BIDSimpleTouchFun.h"
#import "BIDDiscount.h"@implementation BIDRootViewController-(void)loadView
{[super loadView];
　　//self.view=[[[BIDDrawViewalloc] initWithFrame:CGRectMake(0, 0, 320, 460)] autorelease];

    BIDCutView *cutView=[[BIDCutView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];cutView.backgroundColor=[UIColor colorWithPatternImage:[UIImage imageNamed:@"abc.jpg"]];cutView.delegate = self;[self.view addSubview:cutView];[cutView release];
}
- (void)viewDidLoad
{[super viewDidLoad];
}- (void)didReceiveMemoryWarning
{[super didReceiveMemoryWarning];
}-(void)cutImgWithRect:(CGRect)aRect
{UIImage *img=[UIImage imageNamed:@"abc.jpg"];CGImageRef imgRef = img.CGImage;CGImageRef targetImgRef = CGImageCreateWithImageInRect(imgRef, aRect);  //图像的截取UIImage *targetImg=[UIImage imageWithCGImage:targetImgRef];UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, aRect.size.width, aRect.size.height)];imgView.image = targetImg; //把截取得的图像显示到视图中去imgView.tag=1000;[self.view addSubview:imgView];[imgView release];
}-(void)clear
{UIImageView *imgView=(UIImageView *)[self.view viewWithTag:1000];[imgView removeFromSuperview];
}