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。