我正在尝试在照片应用程序中调整图像大小，但尚未成功。我不熟悉在 iOS 上调整照片大小，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];
        }
     }
  };

最佳答案

更新
看起来您忘记了将局部变量 scaleImage 设置为 WUTPostViewController 类的 scaleImage 属性。
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;

   ...
}

原始答案
您的调整大小算法是正确的。我在我的项目中使用了相同的东西并且它完美地工作。
看起来您将 scaleImageToSize: 消息发送到 nil 对象。这就是此消息的结果为 nil 的原因。 您可以通过以这种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 nil，您的应用程序将崩溃并显示提供的消息。
如果 NSAssert 被触发，那么您需要查找问题的根本原因。基本上，您需要在调用 viewDidLoad 方法之前验证 _imageForPost 变量是否已初始化。

关于ios - 在 iOS 上上传到服务器之前调整图像大小，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31713311/