IOS学习笔记（二）取图片

实现动态选取矩形区域内image的功能：

主要思路：因为要随着用户的矩形区域选择，动态显示图片，还要把选择的矩形区域用虚线标识出来，所以要用到重绘（drawRect），then，就需要定义一个UIView的子视图，重写drawRect方法。显示选择区域的部分，用touchBegan，touchMove，touchEnd方法实现。

MyImageView.h

1 @interface MyImageView : UIView

2 @property CGPoint startPoint;

3 @property CGRect rectangle;

4 @property(strong,nonatomic)NSMutableArray *lineArray;

5 @property(strong,nonatomic)UIImage *image;

6 //-(void)setBackgroundImage;

7 @end

MyImageView.m

MyImageView.m

 1 @implementation MyImageView

 2 @synthesize startPoint = _startPoint;

 3 @synthesize rectangle = _rectangle;

 4 @synthesize lineArray = _lineArray;

 5 @synthesize image = _image;

 6 - (id)initWithFrame:(CGRect)frame

 7 {

 8     self = [super initWithFrame:frame];

 9     if (self) {

10         // Initialization code

11 //        UIImage *image = [UIImage imageNamed:@"iphone.jpg"];

12 //        //CGPoint drawPoint = CGPointMake(0, 0);

13 //        [image drawInRect:self.frame];

14     }

15     return self;

16 }

17 

18 // Only override drawRect: if you perform custom drawing.

19 // An empty implementation adversely affects performance during animation.

20 - (void)drawRect:(CGRect)rect

21 {

22     //UIGraphicsBeginImageContext

23     // Drawing code

24     CGContextRef context = UIGraphicsGetCurrentContext();

25     

26     CGFloat dashPhase = 5.0;//dash:破折号 phase:相位

27     CGFloat dashPattern[10] = {10.0,10.0};//

28     size_t dashCount = 2;//dashPattern中的数的个数

29     CGContextSetLineDash(context, dashPhase, dashPattern, dashCount);

30     //CGPoint drawPoint = CGPointMake(0, 0);

31     CGContextAddRect(context, self.rectangle);

32     CGContextSetRGBStrokeColor(context,0,0, 0, 0.5);

33     CGContextSetLineWidth(context, 0.5);

34     CGContextStrokePath(context);

35     

36     

37     CGPoint drawPoint = self.frame.origin;

38     [self.image drawAtPoint:drawPoint];

39     CGContextStrokePath(context);

40     

41 }

42 -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

43 {

44     NSMutableArray *pointArray = [[NSMutableArray alloc]init];

45     UITouch *touch = [touches anyObject];

46     self.startPoint = [touch locationInView:self];

47     NSValue *pointValue = [NSValue valueWithCGPoint:self.startPoint];

48     [pointArray addObject:pointValue];

49     [self.lineArray addObject:pointArray];

50     [pointArray release];

51     

52 }

53 -(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

54 {

55 //    UIGraphicsBeginImageContext(self.rectangle.size);

56 //    UIGraphicsGetCurrentContext();

57 //    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

58 //    self.image = image;

59     UIImage *image = [UIImage imageNamed:@"iphone.jpg"];

60     CGImageRef sourceImageRef = [image CGImage];  

61     CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, self.rectangle);  

62     UIImage *newImage = [UIImage imageWithCGImage:newImageRef];  

63     self.image = newImage;

64     [self setNeedsDisplay];

65 }

66 -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event

67 {

68     UITouch *touch = [touches anyObject];

69     CGPoint endPoint = [touch locationInView:self];

70     NSValue *pointValue = [NSValue valueWithCGPoint:endPoint];

71     NSMutableArray *pointArray = [self.lineArray lastObject];

72     [pointArray addObject:pointValue];

73     float dx =  endPoint.x - self.startPoint.x;

74     float dy = endPoint.y - self.startPoint.y;

75     if(dx > 0 && dy > 0)

76     {

77         self.rectangle = CGRectMake(self.startPoint.x, self.startPoint.y, dx, dy);

78         [self setNeedsDisplay];

79     }

80     

81 }

82 @end