在 iOS 上载到服务器之前调整图像大小

Question

我正在尝试在照片应用中调整图像大小，但尚未成功。我是 iOS 上调整照片大小的新手，但我发誓我做对了，但我的日志显示：

Error: <WUTModelImageUploadReq> 
   [photo]: <nil>
   [extension]: <nil>
</WUTModelImageUploadReq>

我正在尝试将 'scaleImage' 设置为 AsyncPostFeed.m

中的图像

这是我的代码：

UIImage+Scaling.m

@implementation UIImage (Scaling)

- (UIImage *)scaleImageToSize:(CGSize)newSize {

 UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);

 CGFloat originX = 0.0;
 CGFloat originY = 0.0;

 CGRect destinationRect =
 CGRectMake(originX, originY, newSize.width, newSize.height);

 [self drawInRect:destinationRect];

 UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

 UIGraphicsEndImageContext();

 return newImage;
}

@end

WUTPostViewController.m:

- (void)viewDidLoad {
   [super viewDidLoad];

   UIImage *selectedImage = _imageForPost;

   CGSize scaleSize = CGSizeMake(200.0f, 200.0f);

   UIImage *scaleImage =
   [selectedImage scaleImageToSize:scaleSize];

   [self.imageViewForPost setImage:scaleImage];

   ...
}

WUTPostViewController.h:

@interface WUTPostViewController : WUTCommonViewController     <UITextViewDelegate,UIAlertViewDelegate>


@property (strong, nonatomic) IBOutlet UILabel *lblUserName;
@property (strong, nonatomic) IBOutlet UIImageView *imageViewForPost;
@property (strong, nonatomic) IBOutlet UITextView *tvDesription;

@property (strong,nonatomic) UIImage *imageForPost;
@property (strong,nonatomic) UIImage *scaleImage;

- (void)wsPostLikeSuccessCallbackForPostId;
- (void)wsPostLikeFailCallbackWithMessage:(NSString *)errorMessage;


@end

AsyncPostFeed.m:

- (void)uploadPhoto {

   WUTModelImageUploadReq *imageUploadReq = [[WUTModelImageUploadReq alloc]init];
   // I'm trying to set scaleImage here
   imageUploadReq.photo = [self encodeToBase64String:[UIImage imageWithData:UIImageJPEGRepresentation(self.viewControllerPost.scaleImage, 0.07f)]];

   imageUploadReq.extension = @"jpg";

   NSLog(@"Error: %@", imageUploadReq);


   void (^wsSuccessHandler)(AFHTTPRequestOperation *operation, NSDictionary* responseObject) = ^(AFHTTPRequestOperation *operation, id responseObject){
    NSLog(@"Pull Feed responseObject %@",responseObject);

    NSError *error;
    WUTModelPostImageResponse *wsResponse = [[WUTModelPostImageResponse alloc]initWithDictionary:(NSDictionary *)responseObject error:&error];

    if (error) {
        errorMessage = @"Failure to upload image.";
        NSLog(@"Error: %@", error);
        [self postExecuteFail];
    }else{
        if (wsResponse.success) {
            WUTModelImage *imageTemp = [wsResponse.data firstObject];
            [postItem setObject:imageTemp.photo forKey:@"photo"];
            [self uploadPostFeed];

        }else{
            errorMessage = @"Failure to upload image.";
            NSLog(@"Error: %@", error);
            [self postExecuteFail];
        }
     }
  };

Answer 1

请检查第一张图片是否为空

 CGSize size1=CGSizeMake(300,300);
 UIGraphicsBeginImageContext(size1);
 [selectgalleryimage drawInRect:CGRectMake(0, 0,size1.width, size1.height)];
 UIImage *SELECTED_IMG1 = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();

Answer 2

更新
看起来你忘了将局部变量 scaleImage 设置为 scaleImage 属性 of WUTPostViewController class.
试试这段代码（最后一行应该可以解决问题）：

- (void)viewDidLoad {
   [super viewDidLoad];

   UIImage *selectedImage = _imageForPost;

   CGSize scaleSize = CGSizeMake(200.0f, 200.0f);

   UIImage *scaleImage =
   [selectedImage scaleImageToSize:scaleSize];

   [self.imageViewForPost setImage:scaleImage];
   self.scaleImage = scaleImage;

   ...
}

原答案
您的调整大小算法是正确的。我在我的项目中使用了它并且它完美地工作。
看起来您向 nil 对象发送了 scaleImageToSize: 消息。这就是为什么这条消息的结果是 nil.
您可以通过以下方式更新代码来验证此假设：

- (void)viewDidLoad {
   [super viewDidLoad];

   UIImage *selectedImage = _imageForPost;
   NSAssert(selectedImage != nil, @"Selected image is nil");

   CGSize scaleSize = CGSizeMake(200.0f, 200.0f);

   UIImage *scaleImage =
   [selectedImage scaleImageToSize:scaleSize];

   [self.imageViewForPost setImage:scaleImage];

   ...
}

如您所见，我添加了 NSAssert 调用，因此如果所选图像为零，您的应用程序将崩溃并显示提供的消息。
如果触发了 NSAssert，那么您需要查找问题的根本原因。基本上你需要验证 _imageForPost 变量在调用 viewDidLoad 方法之前被初始化。

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