iOS 從相機或相冊獲取圖片並裁剪

今天遇到一個用戶頭像上傳的問題，需要從相冊或者相機中讀取圖片。代碼很簡單，抽取關鍵部分，如下：

//load user image
- (void)UesrImageClicked
{
    UIActionSheet *sheet;
   
    // 判斷是否支持相機
    if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
    {
        sheet  = [[UIActionSheet alloc] initWithTitle:@"選擇圖像" delegate:self cancelButtonTitle:nil destructiveButtonTitle:@"取消" otherButtonTitles:@"拍照", @"從相冊選擇", nil];
    }
    else {
        sheet = [[UIActionSheet alloc] initWithTitle:@"選擇圖像" delegate:self cancelButtonTitle:nil destructiveButtonTitle:@"取消" otherButtonTitles:@"從相冊選擇", nil];
    }
   
    sheet.tag = 255;
   
    [sheet showInView:self.view];
}

#pragma mark - action sheet delegte
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
    if (actionSheet.tag == 255) {
        NSUInteger sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        // 判斷是否支持相機
        if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
            switch (buttonIndex) {
                case 0:
                    return;
                case 1: //相機
                    sourceType = UIImagePickerControllerSourceTypeCamera;
                    break;
                case 2: //相冊
                    sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
                    break;
            }
        }
        else {
            if (buttonIndex == 0) {
                return;
            } else {
                sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
            }
        }
        // 跳轉到相機或相冊頁面
        UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init];
        imagePickerController.delegate = self;
        imagePickerController.allowsEditing = YES;
        imagePickerController.sourceType = sourceType;
       
        [self presentViewController:imagePickerController animated:YES completion:^{}];
    }
}

#pragma mark - image picker delegte
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
 [picker dismissViewControllerAnimated:YES completion:^{}];
   
    UIImage *image = [info UIImagePickerControllerOriginalImage];   
    userImageView.image = image;
   
    NSData *imageData = UIImageJPEGRepresentation(image, COMPRESSED_RATE);
    UIImage *compressedImage = [UIImage imageWithData:imageData];
   
    [HttpRequestManager uploadImage:compressedImage httpClient:self.httpClient delegate:self];
   
}

創建一張表單，選擇相機或者相冊，然後用回調函數處理返回的圖片。

但是返回的圖像並不是正方形，顯示在用戶頭像的View裡面產生明顯的拉伸。研究了很久各種裁剪算法，甚至想創建一個view來處理。突然發現代碼中從相機、相冊獲取圖片時采用的的

UIImagePickerControllerOriginalImage

於是跟蹤進去一看：

UIKIT_EXTERN NSString *const UIImagePickerControllerMediaType;      // an NSString (UTI, i.e. kUTTypeImage)

UIKIT_EXTERN NSString *const UIImagePickerControllerOriginalImage;  // a UIImage

UIKIT_EXTERN NSString *const UIImagePickerControllerEditedImage;    // a UIImage

UIKIT_EXTERN NSString *const UIImagePickerControllerCropRect;      // an NSValue (CGRect)

UIKIT_EXTERN NSString *const UIImagePickerControllerMediaURL;      // an NSURL

UIKIT_EXTERN NSString *const UIImagePickerControllerReferenceURL        NS_AVAILABLE_IOS(4_1);  // an NSURL that references an

很簡單，用UIImagePickerControllerEditedImage，萬事搞定。