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[] = {15.0,5.0};
CGContextSetLineDash(ctx, , lengths, );
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(, , , )];
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(, , 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=;
[self.view addSubview:imgView];
[imgView release];
} -(void)clear
{
UIImageView *imgView=(UIImageView *)[self.view viewWithTag:];
[imgView removeFromSuperview];
}
效果：