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
