iOS 取得单张系统图片

这里主要用到了UIImagePickerController

不多废话，直接上代码

//
//  RootViewController.m
//  GetImageFromPhotoAlbum
//
//  Created by 王云龙 on 16/1/18.
//  Copyright © 2016年 王云龙. All rights reserved.
//

#import "RootViewController.h"
#import "SecViewController.h"

@interface RootViewController ()<UIActionSheetDelegate,UINavigationControllerDelegate, UIImagePickerControllerDelegate>

{
    UIImageView *_imageView;
    UIImageView *_imageViewR;
}

@end

@implementation RootViewController


/**
 *  1.导航器
 *  2.UIImagePickerController
 *  3.iOS文件存取，沙盒机制
 */

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
#pragma mark - 导航器设置
    [self.navigationController.navigationBar setTranslucent:NO];//设置navigationbar的半透明
    NSLog(@"frame = %@,bounds = %@",NSStringFromCGRect(self.view.frame),NSStringFromCGRect(self.view.window.bounds));
    self.title = @"navigationcontroller";//设置navigationbar上显示的标题
    [self.navigationController.navigationBar setBarTintColor:[UIColor purpleColor]];//设置navigationbar的颜色
    
    UIBarButtonItem *left = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(leftAction:)];
    self.navigationItem.leftBarButtonItem = left; //设置navigationbar左边按钮
    
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemCamera target:self action:@selector(rightAction:)];//设置navigationbar右边按钮
    [self.navigationController.navigationBar setTintColor:[UIColor whiteColor]];//设置navigationbar上左右按钮字体颜色
    
#pragma mark - 画面初始化
    _imageViewR = [[UIImageView alloc]initWithFrame:CGRectMake(16, 20, 100, 100)];
    _imageViewR.backgroundColor = [UIColor grayColor];
    [self.view addSubview:_imageViewR];
    
    _imageView = [[UIImageView alloc]initWithFrame:CGRectMake(16, 140, self.view.frame.size.width-32, self.view.frame.size.width-32)];
    _imageView.backgroundColor = [UIColor grayColor];
    [self.view addSubview:_imageView];
    
    UIButton *btn = [UIButton buttonWithType:UIButtonTypeSystem];
    btn.frame = CGRectMake(16, CGRectGetMaxY(_imageView.frame)+20, self.view.frame.size.width-32, 35);
    btn.layer.cornerRadius = 5;
    btn.layer.masksToBounds = YES;
    [btn setTitle:@"获取相册图片" forState:UIControlStateNormal];
    [btn addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    
}

#pragma mark - 导航控制器的跳转
-(void)leftAction:(UIBarButtonItem*)sender{
    //只能跳到没有没有导航控制器的controller
    SecViewController *secVC = [[SecViewController alloc]init];
    [self.navigationController pushViewController:secVC animated:YES];
}

-(void)rightAction:(UIBarButtonItem*)sender{
    //相册
    UIImagePickerController *imagePickController = [[UIImagePickerController alloc]init];
    imagePickController.delegate = self;
    imagePickController.allowsEditing = YES;
    imagePickController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    [self presentViewController:imagePickController animated:YES completion:nil
     ];
    
    
}

#pragma mark - 相册中取得图片并显示
-(void)btnAction:(UIButton*)sender{
    
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"获取图片" message:nil preferredStyle:UIAlertControllerStyleActionSheet];
    
    //判断支持类型
    //相册和图库的区别
    //http://zhidao.baidu.com/link?url=DGZvUPsBPpArTyqP5ff2BcbVL1s_OUuH9A4TfB3Bn0xTP_iylo7Y45wAShBGZXDW85cicNPaeXSQlLiPzYCvCbDmA9gPHX5042sNfrN5ZFu
    
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
        NSLog(@"支持相机");
    else
        NSLog(@"不支持相机");
    
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary])
        NSLog(@"支持图库");
    else
        NSLog(@"不支持图库");
    
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeSavedPhotosAlbum])
        NSLog(@"支持相册");
    else
        NSLog(@"不支持相册");
    
    
    
    //判断是否支持相机
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
        UIAlertAction*defualtAction = [UIAlertAction actionWithTitle:@"拍照" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            UIImagePickerController *imagePickerController = [[UIImagePickerController alloc]init];
            imagePickerController.delegate = self;
            imagePickerController.allowsEditing = YES;
            imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
            [self presentViewController:imagePickerController animated:YES completion:^{}];
        }];
        [alertController addAction:defualtAction];
    }
    UIAlertAction *defaultAction1 = [UIAlertAction actionWithTitle:@"从相册选择" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        //相册
        UIImagePickerController *imagePickController = [[UIImagePickerController alloc]init];
        imagePickController.delegate = self;
        imagePickController.allowsEditing = YES;
        imagePickController.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
        [self presentViewController:imagePickController animated:YES completion:nil
         ];
        
    }];
    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:nil];
    [alertController addAction:cancelAction];
    [alertController addAction:defaultAction1];
    
    //弹出视图
    [self presentViewController:alertController animated:YES completion:nil];
    
}

#pragma mark - 文件保存到本地
//http://blog.csdn.net/jianjianyuer/article/details/8556024
-(void)saveImage:(UIImage*)currentImage withName:(NSString*)name{
    //图片读取的两个方法
    //http://blog.csdn.net/lovenjoe/article/details/7484217
    //NSData存储二进制数据
    //http://blog.csdn.net/jjmm2009/article/details/39004149
    NSData *imageData = UIImagePNGRepresentation(currentImage);
    
    //沙盒介绍
    //http://www.cnblogs.com/taintain1984/archive/2013/03/19/2969201.html
    NSString *fullPath = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:name];
    
    //沙盒文件操作
    //http://www.cocoachina.com/bbs/read.php?tid-78784.html
    
    //将图片写入
    [imageData writeToFile:fullPath atomically:YES];
}

#pragma mark - UIImagePickerController的代理方法。
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info{
    
    [picker dismissViewControllerAnimated:YES completion:nil];
    //得到原始图片，未编辑的
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    
    //判断是否图片已经读取过
    NSString*referenceURL = [info objectForKey:UIImagePickerControllerReferenceURL];
    NSLog(@"%@",referenceURL);
    //保存图片到本地
    //文件名为时间戳，防止重名
    NSDate *datenow = [NSDate date];
    NSString *timeSp = [NSString stringWithFormat:@"%lf",[datenow timeIntervalSince1970]];
    NSString *fileName = [NSString stringWithFormat:@"%@.png",timeSp];
    
    [self saveImage:image withName:fileName];
    
    NSString *fullPath = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:fileName];
    
    
    UIImage *saveImage = [[UIImage alloc]initWithContentsOfFile:fullPath];

    //设置图片显示
    [_imageView setImage:saveImage];
    [_imageViewR setImage:image];
}

-(void)imagePickerControllerDidCancel:(UIImagePickerController *)picker{
    [picker dismissViewControllerAnimated:YES completion:nil];
}


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


@end

注意点

需要设置的三个重要属性

delegate:代理，必须设置，否则选择图片后页面跳转不会来，也取不到选取的图片

allowEditing:最好设置为yes，否则看不到原图，只能在图片墙上选取图片

souceType:图片来源，有三个，照片流，图库，相机，区别和用法请参考代码

两个重要的代理方法

请参考代码，但是两个代理方法中都要写模态跳转，系统是不会自己跳回来的。