iOS相机功能开发全解析

### iOS 相机功能开发全解析 #### 1. UIImagePickerController 基础使用 当在真机上运行应用并点击按钮时，会弹出一个简单的相机界面，可用于拍照并选择照片用于应用，若不满意还能重拍。以下是具体操作步骤和代码实现： - **获取照片**：设置视图控制器以成功展示 `UIImagePickerController` 后，需处理视图控制器对 `UIImagePickerController` 选择完成的响应。使用 `imagePickerController:didFinishPickingMediaWithInfo:` 委托方法来获取照片、更新图像视图并关闭图像选择器。 ```objc -(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage]; self.imageView.image = image; self.imageView.contentMode = UIViewContentModeScaleAspectFill; [self dismissViewControllerAnimated:YES completion:NULL]; } ``` 设置图像视图的 `contentMode` 为 `UIViewContentModeScaleAspectFill` 可确保图片在保持宽高比的同时填充整个视图，通常会裁剪图片而非拉伸。也可使用 `UIViewContentModeScaleAspectFit`，它能显示完整图片且保持宽高比，但不一定填充整个视图。 - **处理取消选择**：还需实现 `imagePickerControllerDidCancel:` 委托方法来处理图像选择的取消操作，只需关闭图像选择器视图。 ```objc - (void) imagePickerControllerDidCancel: (UIImagePickerController *) picker { [self dismissViewControllerAnimated:YES completion:NULL]; } ``` #### 2. 基本编辑功能实现 可将相机界面设置为可编辑，使用户能裁剪和构图拍摄的照片。操作步骤如下： - **允许编辑**：将 `UIImagePickerController` 的 `allowsEditing` 属性设置为 `YES`。 ```objc - (IBAction)takePicture:(id)sender { // ... if (self.imagePicker == nil) { self.imagePicker = [[UIImagePickerController alloc] init]; self.imagePicker.delegate = self; self.imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera; self.imagePicker.allowsEditing = YES; } [self presentViewController:self.imagePicker animated:YES completion:NULL]; } ``` - **获取编辑后的图像**：修改 `imagePickerController:didFinishPickingMediaWithInfo:` 方法以获取编辑后的图像。 ```objc -(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { UIImage *image = [info objectForKey:UIImagePickerControllerEditedImage]; self.imageView.image = image; self.imageView.contentMode = UIViewContentModeScaleAspectFill; [self dismissViewControllerAnimated:YES completion:NULL]; } ``` #### 3. 保存照片到相册 可使用 `UIImageWriteToSavedPhotosAlbum()` 函数将拍摄的照片保存到设备的相册。操作步骤如下： - **修改获取照片方法**：在 `imagePickerController:didFinishPickingMediaWithInfo:` 方法中添加保存代码。 ```objc -(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { UIImage *image = (UIImage *)[info objectForKey:UIImagePickerControllerEditedImage]; UIImageWriteToSavedPhotosAlbum (image, nil, nil , nil); self.imageView.image = image; self.imageView.contentMode = UIViewContentModeScaleAspectFill; [self dismissViewControllerAnimated:YES completion:NULL]; } ``` - **隐私授权**：从 iOS 6 开始，访问相册有隐私限制，应用需获得用户明确授权。在应用的 `Info.plist` 文件中添加 `NSPhotoLibraryUsageDescription` 键，并提供应用请求访问相册的原因说明。 #### 4. 录制视频功能实现 `UIImagePickerController` 不仅可用于拍摄静态图像，还能处理视频。以下是设置 `UIImagePickerController` 处理静态图像和视频的步骤： - **允许视频录制**：更新 `takePicture:` 方法，设置图像选择器允许的媒体类型为相机的所有可用类型。 ```objc - (IBAction)takePicture:(id)sender { // Make sure camera is available if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera] == NO) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Camera Unavailable" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil, nil]; [alert show]; return; } if (self.imagePicker == nil) { self.imagePicker = [[UIImagePickerController alloc] init]; self.imagePicker.delegate = self; self.imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera; self.imagePicker.mediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera]; self.imagePicker.allowsEditing = YES; } [self presentViewController:self.imagePicker animated:YES completion:NULL]; } ``` - **导入框架**：将 `Mobile Core Services` 框架链接到项目，并在视图控制器的头文件中导入其 API。 ```objc // // ViewController.h // Recipe 9-2 Recording Videos // #import <UIKit/UIKit.h> #import <MobileCoreServices/MobileCoreServices.h> @interface ViewController : UIViewController<UIImagePickerControllerDelegate, UINavigationControllerDelegate> @property (weak, nonatomic) IBOutlet UIImageView *imageView; @property (weak, nonatomic) IBOutlet UIButton *cameraButton; @property (strong, nonatomic) UIImagePickerController *imagePicker; - (IBAction)takePicture:(id)sender; @end ``` - **处理视频录制完成**：修改 `imagePickerController:didFinishPickingMediaWithInfo:` 方法，根据媒体类型处理视频和照片。 ```objc -(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { NSString *mediaType = [info objectForKey: UIImagePickerControllerMediaType]; if (CFStringCompare((__bridge CFStringRef) mediaType, kUTTypeMovie, 0) == kCFCompareEqualTo) { // Movie Captured NSString *moviePath = (NSString *) [[info objectForKey: UIImagePickerControllerMediaURL] path]; if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum (moviePath)) { UISaveVideoAtPathToSavedPhotosAlbum (moviePath, nil, nil, nil); } } else { // Picture Taken UIImage *image = (UIImage *)[info objectForKey:UIImagePickerControllerEditedImage]; UIImageWriteToSavedPhotosAlbum (image, nil, nil , nil); self.imageView.image = image; self.imageView.contentMode = UIViewContentModeScaleAspectFill; } [self dismissViewControllerAnimated:YES completion:NULL]; } ``` #### 5. 视频编辑功能实现 虽然 `UIImagePickerController` 可录制和保存视频文件，但无法编辑。可使用 `UIVideo