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

#import "MyView.h"

@implementation MyView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    // Draw rectangle
    CGRect drawingRect = CGRectMake(0.0, 20.0f, 100.0f, 180.0f);
    const CGFloat *rectColorComponents = CGColorGetComponents([[UIColor greenColor] CGColor]);
    CGContextSetFillColor(context, rectColorComponents);
    CGContextFillRect(context, drawingRect);
    // Draw ellipse
    CGRect ellipseRect = CGRectMake(140.0f, 200.0f, 75.0f, 50.0f);
    const CGFloat *ellipseColorComponenets = CGColorGetComponents([[UIColor blueColor] CGColor]);
    CGContextSetFillColor(context, ellipseColorComponenets);
    CGContextFillEllipseInRect(context, ellipseRect);
    // Draw parallelogram
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, 0.0f, 0.0f);
    CGContextAddLineToPoint(context, 100.0f, 0.0f);
    CGContextAddLineToPoint(context, 140.0f, 100.0f);
    CGContextAddLineToPoint(context, 40.0f, 100.0f);
    CGContextClosePath(context);
    CGContextSetGrayFillColor(context, 0.4f, 0.85f);
    CGContextSetGrayStrokeColor(context, 0.0, 0.0);
    CGContextFillPath(context);
    
    if (self.image)
    {
        CGFloat imageWidth = self.frame.size.width / 2;
        CGFloat imageHeight = self.frame.size.height / 2;
        CGRect imageRect = CGRectMake(imageWidth, imageHeight, imageWidth, imageHeight);
        [self.image drawInRect:imageRect];
    }
}

@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

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (BOOL) canBecomeFirstResponder
{
    return YES;
}

- (void) viewWillAppear: (BOOL)animated
{
    [self.view becomeFirstResponder];
    [super viewWillAppear:animated];
}

- (void) viewWillDisappear: (BOOL)animated
{
    [self.view resignFirstResponder];
    [super viewWillDisappear:animated];
}

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
    if (event.subtype == UIEventSubtypeMotionShake)
    {
        // Device was shaken
        
        // Acquire image of current layer
        UIGraphicsBeginImageContext(self.view.bounds.size);
        CGContextRef context = UIGraphicsGetCurrentContext();
        [self.view.layer renderInContext:context];
        //截图方法
        UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        
        self.myView.image =  image;
        //UIView重新调用drawRect方法，从而包含最新的变化。
        [self.myView setNeedsDisplay];

    }
}

@end