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：
[cpp]view plaincopy
1.//load user image
2.- (void)UesrImageClicked
3.{
4. UIActionSheet *sheet;
5.
6.// 判断是否支持相机
7.if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControlle
rSourceTypeCamera])
8. {
9. sheet = [[UIActionSheet alloc] initWithTitle:@"选择图像
" delegate:self cancelButtonTitle:nil destructiveButtonTitle:@"取消
" otherButtonTitles:@"拍照", @"从相册选择", nil];
10. }
11.else {
12. sheet = [[UIActionSheet alloc] initWithTitle:@"选择图像
" delegate:self cancelButtonTitle:nil destructiveButtonTitle:@"取消
" otherButtonTitles:@"从相册选择", nil];
13. }
14.
15. sheet.tag = 255;
16.
17. [sheet showInView:self.view];
18.}
19.
20.
21.#pragma mark - action sheet delegte
22.- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInt
eger)buttonIndex
23.{
24.if (actionSheet.tag == 255) {
25. NSUInteger sourceType = UIImagePickerControllerSourceTypePhotoLibrar
y;
26.// 判断是否支持相机
27.if([UIImagePickerController isSourceTypeAvailable:UIImagePickerContr
ollerSourceTypeCamera]) {
28.switch (buttonIndex) {
29.case 0:
30.return;
31.case 1: //相机
32. sourceType = UIImagePickerControllerSourceTypeCamera;
33.break;
34.case 2: //相册
35. sourceType = UIImagePickerControllerSourceTypePhotoLibra
ry;
36.break;
37. }
38. }
39.else {
40.if (buttonIndex == 0) {
41.return;
42. } else {
43. sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlb
um;
44. }
45. }
46.// 跳转到相机或相册页面
47. UIImagePickerController *imagePickerController = [[UIImagePickerCont
roller alloc] init];
48. imagePickerController.delegate = self;
49. imagePickerController.allowsEditing = YES;
50. imagePickerController.sourceType = sourceType;
51.
52. [self presentViewController:imagePickerController animated:YES compl
etion:^{}];
53. }
54.}
55.
56.#pragma mark - image picker delegte
57.- (void)imagePickerController:(UIImagePickerController *)picker didFinishPic
kingMediaWithInfo:(NSDictionary *)info
58.{
59. [picker dismissViewControllerAnimated:YES completion:^{}];
60.
61. UIImage *image = [info UIImagePickerControllerOriginalImage];
62. userImageView.image = image;
63.
64. NSData *imageData = UIImageJPEGRepresentation(image, COMPRESSED_RATE);
65. UIImage *compressedImage = [UIImage imageWithData:imageData];
66.
67. [HttpRequestManager uploadImage:compressedImage httpClient:self.httpClie
nt delegate:self];
68.
69.}
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。