iOS在圖片中添加水印

- (void)viewDidLoad

{

    [super viewDidLoad];

    //背景圖片

    UIImage *bgImage=[UIImage imageNamed:@"QQ20140413-4"];

    /**

     *  創建一個基於位圖的上下文

       size 新圖片的尺寸

       opaque:YES ：不透明  NO:透明

     */

    UIGraphicsBeginImageContextWithOptions(bgImage.size, YES, 0.0);

    // 畫背景圖片

    [bgImage drawInRect:CGRectMake(0, 0, bgImage.size.width, bgImage.size.height)];

    //畫logo

    UIImage *logoImage=[UIImage imageNamed:@"logo"];

    CGFloat logoW=logoImage.size.width*0.3;

    CGFloat logoH=logoImage.size.height*0.3;

    CGFloat logoX=bgImage.size.width-logoW-10;

    CGFloat logoY=bgImage.size.height-logoH-10;

    [logoImage drawInRect:CGRectMake(logoX, logoY, logoW, logoH)];

    // 畫的新圖片 從上下文中取得製作完畢的uiImage對象

   UIImage *newImage= UIGraphicsGetImageFromCurrentImageContext();

    // 結束上下文

    UIGraphicsEndImageContext();

    //添加到視圖

    UIImageView *iconImage=[[UIImageView alloc]init];

    iconImage.frame=CGRectMake(0, 100, bgImage.size.width, bgImage.size.height);

    iconImage.image=newImage;

    [self.view addSubview:iconImage];

    //將iconImage壓縮成二進制文件

    NSData *iconData=UIImagePNGRepresentation(newImage);

    //寫入文件

    NSString *path=[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"abc.png"];

    [iconData writeToFile:path atomically:YES];

}