使用圖像

為了便于操作對(duì)象，iOS中定義了圖像類：
UIImage（UIKit框架中定義的圖像類）
CGImage（在Core Graphics框架（或Quartz 2D）中定義的圖像類）
CIImage(Core Image)
以上三者之間可以相互轉(zhuǎn)化。

創(chuàng)建圖像的四種方式

1.從資源文件中直接加載
2.從應(yīng)用程序沙盒目錄加載
3.從云服務(wù)器端獲取
4.從設(shè)備圖片庫(kù)選取或從照相機(jī)抓取

例圖

Swift代碼

import UIKit

let FILE_NAME = "WeChat_1468557469.png"

class ViewController: UIViewController {

    @IBOutlet weak var imageView: UIImageView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        //把資源文件中的圖片復(fù)制到沙河中document目錄下
        self.createEditableCopyOfDatabaseIfNeeded()
        self.imageView.image = UIImage(named:"WeChat_1468557469.png")
        
    }
    func createEditableCopyOfDatabaseIfNeeded() {
        // NSFileManager采用單例設(shè)計(jì)模式
        let fileManager = NSFileManager.defaultManager()
        let writalbeDBPath = applicationDocumentsDirectoryFile()
        let dbexits = fileManager.fileExistsAtPath(writalbeDBPath)
        //如果文件不存在，則copy一個(gè)圖文到沙盒中
        if !dbexits {
        }
    }

    func applicationDocumentsDirectoryFile() -> String {
        let documentDirectorys:NSArray = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
        let documetDirectory = documentDirectorys[0] as!String
        let path = documetDirectory.stringByAppendingString(FILE_NAME)
        
        return path
    }
    
    @IBAction func loadBundle(sender: AnyObject) {
        let path = NSBundle.mainBundle().pathForResource("WeChat_1468557469", ofType: "png")
        var image = UIImage(contentsOfFile: path!)
        self.imageView.image = UIImage(named:"WeChat_1468557469.png")

    }
    @IBAction func loadSandbox(sender: AnyObject) {
        let path = self.applicationDocumentsDirectoryFile()
        self.imageView.image = UIImage(contentsOfFile:path)

    }

    @IBAction func loadWebService(sender: AnyObject) {
        NSLog("從云服務(wù)器中加載圖片")
    }

}

OC代碼

//對(duì)文件進(jìn)行預(yù)處理，判斷在Documents目錄下是否存在plist文件，如果不存在則從資源目錄下復(fù)制一個(gè)。
-(void)createEditableCopyOfDatabaseIfNeeded
{
    NSFileManager *fileManager=[NSFileManager defaultManager];
    NSString *writableDBPath=[self applicationDocumentsDirectoryFile];
    
    BOOL dbexits=[fileManager fileExistsAtPath:writableDBPath];
    if (!dbexits) {
        NSString *defaultDBPath=[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"Contacts.plist"];
        
        NSError *error;
        BOOL success=[fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
        
        if (!success) {            
            NSAssert1(0,@"錯(cuò)誤寫入文件：‘%@’",[error localizedDescription]);
        }
    }
}

//獲取放置在沙箱Documents目錄下的文件的完整路徑
-(NSString *)applicationDocumentsDirectoryFile
{
    NSString *documentDirectory=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path=[documentDirectory stringByAppendingPathComponent:@"Contacts.plist"];
   
    return path;
}