iOS 从相机或相册获取图片并裁剪

今天遇到一个用户头像上传的问题，需要从相册或者相机中读取图片。代码很简单，抽取关键部分，如下：

//load user image
- (void)UesrImageClicked
{
UIActionSheet *sheet;

// 判断是否支持相机
if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
{
sheet  = [[UIActionSheet alloc] initWithTitle:@"选择图像" delegate:self cancelButtonTitle:nil destructiveButtonTitle:@"取消" otherButtonTitles:@"拍照", @"从相册选择", nil];
}
else {
sheet = [[UIActionSheet alloc] initWithTitle:@"选择图像" delegate:self cancelButtonTitle:nil destructiveButtonTitle:@"取消" otherButtonTitles:@"从相册选择", 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;
// 判断是否支持相机
if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
switch (buttonIndex) {
case 0:
return;
case 1: //相机
sourceType = UIImagePickerControllerSourceTypeCamera;
break;
case 2: //相册
sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
break;
}
}
else {
if (buttonIndex == 0) {
return;
} else {
sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
}
}
// 跳转到相机或相册页面
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];

}

创建一张表单，选择相机或者相册，然后用回调函数处理返回的图片。

但是返回的图像并不是正方形，显示在用户头像的View里面产生明显的拉伸。研究了很久各种裁剪算法，甚至想创建一个view来处理。突然发现代码中从相机、相册获取图片时采用的的

UIImagePickerControllerOriginalImage

于是跟踪进去一看：

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

恍然大悟，很简单，用UIImagePickerControllerEditedImage，万事搞定。