图像攻略

1、绘制简单的形状

#import <UIKit/UIKit.h>

@interface MyView : UIView

@property (strong, nonatomic)UIImage *image;

@end

 1 #import "MyView.h"
 2 
 3 @implementation MyView
 4 
 5 - (id)initWithFrame:(CGRect)frame
 6 {
 7     self = [super initWithFrame:frame];
 8     if (self) {
 9         // Initialization code
10     }
11     return self;
12 }
13 
14 // Only override drawRect: if you perform custom drawing.
15 // An empty implementation adversely affects performance during animation.
16 - (void)drawRect:(CGRect)rect
17 {
18     CGContextRef context = UIGraphicsGetCurrentContext();
19     // Draw rectangle
20     CGRect drawingRect = CGRectMake(0.0, 20.0f, 100.0f, 180.0f);
21     const CGFloat *rectColorComponents = CGColorGetComponents([[UIColor greenColor] CGColor]);
22     CGContextSetFillColor(context, rectColorComponents);
23     CGContextFillRect(context, drawingRect);
24     // Draw ellipse
25     CGRect ellipseRect = CGRectMake(140.0f, 200.0f, 75.0f, 50.0f);
26     const CGFloat *ellipseColorComponenets = CGColorGetComponents([[UIColor blueColor] CGColor]);
27     CGContextSetFillColor(context, ellipseColorComponenets);
28     CGContextFillEllipseInRect(context, ellipseRect);
29     // Draw parallelogram
30     CGContextBeginPath(context);
31     CGContextMoveToPoint(context, 0.0f, 0.0f);
32     CGContextAddLineToPoint(context, 100.0f, 0.0f);
33     CGContextAddLineToPoint(context, 140.0f, 100.0f);
34     CGContextAddLineToPoint(context, 40.0f, 100.0f);
35     CGContextClosePath(context);
36     CGContextSetGrayFillColor(context, 0.4f, 0.85f);
37     CGContextSetGrayStrokeColor(context, 0.0, 0.0);
38     CGContextFillPath(context);
39     
40     if (self.image)
41     {
42         CGFloat imageWidth = self.frame.size.width / 2;
43         CGFloat imageHeight = self.frame.size.height / 2;
44         CGRect imageRect = CGRectMake(imageWidth, imageHeight, imageWidth, imageHeight);
45         [self.image drawInRect:imageRect];
46     }
47 }
48 
49 @end

2、屏幕截图编程

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
#import "MyView.h"

@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet MyView *myView;

@end

 1 #import "ViewController.h"
 2 
 3 @interface ViewController ()
 4 
 5 @end
 6 
 7 @implementation ViewController
 8 
 9 - (void)viewDidLoad
10 {
11     [super viewDidLoad];
12     // Do any additional setup after loading the view, typically from a nib.
13 }
14 
15 - (void)didReceiveMemoryWarning
16 {
17     [super didReceiveMemoryWarning];
18     // Dispose of any resources that can be recreated.
19 }
20 
21 - (BOOL) canBecomeFirstResponder
22 {
23     return YES;
24 }
25 
26 - (void) viewWillAppear: (BOOL)animated
27 {
28     [self.view becomeFirstResponder];
29     [super viewWillAppear:animated];
30 }
31 
32 - (void) viewWillDisappear: (BOOL)animated
33 {
34     [self.view resignFirstResponder];
35     [super viewWillDisappear:animated];
36 }
37 
38 - (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
39 {
40     if (event.subtype == UIEventSubtypeMotionShake)
41     {
42         // Device was shaken
43         
44         // Acquire image of current layer
45         UIGraphicsBeginImageContext(self.view.bounds.size);
46         CGContextRef context = UIGraphicsGetCurrentContext();
47         [self.view.layer renderInContext:context];
48         //截图方法
49         UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
50         UIGraphicsEndImageContext();
51         
52         self.myView.image =  image;
53         //UIView重新调用drawRect方法，从而包含最新的变化。
54         [self.myView setNeedsDisplay];
55 
56     }
57 }
58 
59 @end