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

//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;