iOS实现头像选取（照相或者图片库）、大小等比缩放、生成圆形头像

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//弹出actionsheet。选择获取头像的方式
//从相册获取图片
-(void)takePictureClick:(UIButton *)sender
{
//	/*注：使用，需要实现以下协议：UIImagePickerControllerDelegate,
//	 UINavigationControllerDelegate
//	 */
//	UIImagePickerController *picker = [[UIImagePickerController alloc]init];
//	//设置图片源(相簿)
//	picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
//	//设置代理
//	picker.delegate = self;
//	//设置可以编辑
//	picker.allowsEditing = YES;
//	//打开拾取器界面
//	[self presentViewController:picker animated:YES completion:nil];
  UIActionSheet* actionSheet = [[UIActionSheet alloc]
                  initWithTitle:@"请选择文件来源"
                  delegate:self
                  cancelButtonTitle:@"取消"
                  destructiveButtonTitle:nil
                  otherButtonTitles:@"照相机",@"摄像机",@"本地相簿",@"本地视频",nil];
  [actionSheet showInView:self.view];
  
}
#pragma mark -
#pragma UIActionSheet Delegate
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
  NSLog(@"buttonIndex = [%d]",buttonIndex);
  switch (buttonIndex) {
    case 0://照相机
    {
      UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
      imagePicker.delegate = self;
      imagePicker.allowsEditing = YES;
      imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
//			[self presentModalViewController:imagePicker animated:YES];
      [self presentViewController:imagePicker animated:YES completion:nil];
    }
      break;
    case 1://摄像机
    {
      UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
      imagePicker.delegate = self;
      imagePicker.allowsEditing = YES;
      imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
      imagePicker.videoQuality = UIImagePickerControllerQualityTypeLow;
//			[self presentModalViewController:imagePicker animated:YES];
      [self presentViewController:imagePicker animated:YES completion:nil];
    }
      break;
    case 2://本地相簿
    {
      UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
      imagePicker.delegate = self;
      imagePicker.allowsEditing = YES;
      imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
//			[self presentModalViewController:imagePicker animated:YES];
      [self presentViewController:imagePicker animated:YES completion:nil];
    }
      break;
    case 3://本地视频
    {
      UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
      imagePicker.delegate = self;
      imagePicker.allowsEditing = YES;
      imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
//			[self presentModalViewController:imagePicker animated:YES];
      [self presentViewController:imagePicker animated:YES completion:nil];
    }
      break;
    default:
      break;
  }
}

#pragma mark -
#pragma UIImagePickerController Delegate
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
  if ([[info objectForKey:UIImagePickerControllerMediaType] isEqualToString:(__bridge NSString *)kUTTypeImage]) {
    UIImage *img = [info objectForKey:UIImagePickerControllerEditedImage];
    [self performSelector:@selector(saveImage:)  withObject:img afterDelay:0.5];
  }
  else if ([[info objectForKey:UIImagePickerControllerMediaType] isEqualToString:(__bridge NSString *)kUTTypeMovie]) {
    NSString *videoPath = [[info objectForKey:UIImagePickerControllerMediaURL] path];
    self.fileData = [NSData dataWithContentsOfFile:videoPath];
  }
//	[picker dismissModalViewControllerAnimated:YES];
  [picker dismissViewControllerAnimated:YES completion:nil];
}

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{
//	[picker dismissModalViewControllerAnimated:YES];
    [picker dismissViewControllerAnimated:YES completion:nil];
}

- (void)saveImage:(UIImage *)image {
  //	NSLog(@"保存头像！");
  //	[userPhotoButton setImage:image forState:UIControlStateNormal];
  BOOL success;
  NSFileManager *fileManager = [NSFileManager defaultManager];
  NSError *error;
  
  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *documentsDirectory = [paths objectAtIndex:0];
  NSString *imageFilePath = [documentsDirectory stringByappendingPathComponent:@"selfPhoto.jpg"];
  NSLog(@"imageFile->>%@",imageFilePath);
  success = [fileManager fileExistsAtPath:imageFilePath];
  if(success) {
    success = [fileManager removeItemAtPath:imageFilePath error:&error];
  }
//	UIImage *smallImage=[self scaleFromImage:image toSize:CGSizeMake(80.0f, 80.0f)];//将图片尺寸改为80*80
  UIImage *smallImage = [self thumbnailWithImageWithoutScale:image size:CGSizeMake(93, 93)];
  [UIImageJPEgrepresentation(smallImage, 1.0f) writeToFile:imageFilePath atomically:YES];//写入文件
  UIImage *selfPhoto = [UIImage imageWithContentsOfFile:imageFilePath];//读取图片文件
//	[userPhotoButton setImage:selfPhoto forState:UIControlStateNormal];
  self.img.image = selfPhoto;
}

// 改变图像的尺寸，方便上传服务器
- (UIImage *) scaleFromImage: (UIImage *) image toSize: (CGSize) size
{
  UIGraphicsBeginImageContext(size);
  [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return newImage;
}

2.保持原始图片的长宽比，生成需要尺寸的图片

//2.保持原来的长宽比，生成一个缩略图
- (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)asize
{
  UIImage *newimage;
  if (nil == image) {
    newimage = nil;
  }
  else{
    CGSize oldsize = image.size;
    CGRect rect;
    if (asize.width/asize.height > oldsize.width/oldsize.height) {
      rect.size.width = asize.height*oldsize.width/oldsize.height;
      rect.size.height = asize.height;
      rect.origin.x = (asize.width - rect.size.width)/2;
      rect.origin.y = 0;
    }
    else{
      rect.size.width = asize.width;
      rect.size.height = asize.width*oldsize.height/oldsize.width;
      rect.origin.x = 0;
      rect.origin.y = (asize.height - rect.size.height)/2;
    }
    UIGraphicsBeginImageContext(asize);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);
    UIRectFill(CGRectMake(0, 0, asize.width, asize.height));//clear background
    [image drawInRect:rect];
    newimage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
  }
  return newimage;
}

3.显示圆形头像

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *documentsDirectory = [paths objectAtIndex:0];
  NSString *imageFilePath = [documentsDirectory stringByAppendingPathComponent:@"selfPhoto.jpg"];
 NSLog(@"imageFile->>%@",imageFilePath);
  UIImage *selfPhoto = [UIImage imageWithContentsOfFile:imageFilePath];//
  self.img.image = selfPhoto;
  [self.img.layer setCornerRadius:CGRectGetHeight([self.img bounds]) / 2];  //修改半径，实现头像的圆形化
  self.img.layer.masksToBounds = YES;