UIImagePickerController
－－ the only sanctioned way to get videos/movies or images/pictures on supported devices
<UIImagePickerControllerDelegate,UINavigationControllerDelegate>

用UIImagePickerController选择、显示图片或视频，主要注意UIImagePickerController几个属性的设置

一：UI 显示样式，显示的格式确定

1：sourceType

@property(nonatomic) UIImagePickerControllerSourceType sourceType
enum {
UIImagePickerControllerSourceTypePhotoLibrary,
UIImagePickerControllerSourceTypeCamera,
UIImagePickerControllerSourceTypeSavedPhotosAlbum
};
typedef NSUInteger UIImagePickerControllerSourceType;

sourceType用来确定用户界面显示的样式：

共三种格式（模拟器上的效果图）

UIImagePickerControllerSourceTypePhotoLibrary,
UIImagePickerControllerSourceTypeCamera,
 UIImagePickerControllerSourceTypeSavedPhotosAlbum

为了区分是否支持视频格式，一般要用到下面这个函数，以便确定mediaTypes。
+ (BOOL)isSourceTypeAvailable:(UIImagePickerControllerSourceType)sourceType
2:   mediaTypes
@property(nonatomic,copy) NSArray *mediaTypes
mediaTypes用来确定再picker里显示那些类型的多媒体文件，图片？视频？
+ (NSArray *)availableMediaTypesForSourceType:(UIImagePickerControllerSourceType)sourceType
二：选取动作处理
UIImagePickerControllerDelegate
通过代理来完成用户在选中图片，或者choose视频时的处理方式：
共有三个可选的代理方法

– imagePickerController:didFinishPickingMediaWithInfo:  
 – imagePickerControllerDidCancel:  
 – imagePickerController:didFinishPickingImage:editingInfo:   Deprecated in iPhone OS 3.0
 - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info


info中包括选取的照片，视频的主要信息

NSString *const UIImagePickerControllerMediaType;         选取的类型 public.image  public.movie
 NSString *const UIImagePickerControllerOriginalImage;    修改前的UIImage object.
 NSString *const UIImagePickerControllerEditedImage;      修改后的UIImage object.
 NSString *const UIImagePickerControllerCropRect;           原始图片的尺寸NSValue object containing a CGRect data type
 NSString *const UIImagePickerControllerMediaURL;          视频在文件系统中 的 NSURL地址


保存视频主要时通过获取其NSURL 然后转换成NSData
实例代码如下：

- (void) pickImage: (id) sender
 {
 UIImagePickerController *ipc = [[UIImagePickerController alloc] init];
         if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]){
      ipc.sourceType =  UIImagePickerControllerSourceTypePhotoLibrary;
       ipc.mediaTypes =[UIImagePickerController availableMediaTypesForSourceType:ipc.sourceType];   
         } 
 ipc.delegate = self;
 ipc.allowsImageEditing = NO;
 [self presentModalViewController:ipc animated:YES]; 
 }
 - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
 {
 NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];
 if ([mediaType isEqualToString:@"public.image"]){
 // UIImage *selectedImage = [info objectForKey:UIImagePickerControllerOriginalImage];
 UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
     NSLog(@"found an image");
 [UIImageJPEGRepresentation(image, 1.0f) writeToFile:[self findUniqueSavePath] atomically:YES];
     SETIMAGE(image);
 CFShow([[NSFileManager defaultManager] directoryContentsAtPath:[NSHomeDirectory() stringByAppendingString:@"/Documents"]]);
 }
 else if ([mediaType isEqualToString:@"public.movie"]){
 NSURL *videoURL = [info objectForKey:UIImagePickerControllerMediaURL];
 NSLog(@"found a video");
         NSData *webData = [NSData dataWithContentsOfURL:videoURL];
 //NSData *video = [[NSString alloc] initWithContentsOfURL:videoURL];
 [webData writeToFile:[self findUniqueMoviePath] atomically:YES];
 CFShow([[NSFileManager defaultManager] directoryContentsAtPath:[NSHomeDirectory() stringByAppendingString:@"/Documents"]]);
 // NSLog(videoURL);
 }
 [picker dismissModalViewControllerAnimated:YES];
 }