Question

在我的应用程序中，当我使用UIImagePickerController时，我调整从拾取器中获取的图像的大小，以便从它开始的非常大的尺寸减少它。在iPhone和iPod Touch上，它工作正常，并且存在轻微的延迟。但是，由于iPad屏幕要大得多，因此根据像素调整大小，因此需要更长时间。

这是我的代码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    CGRect screenBounds = [[UIScreen mainScreen] bounds];
    CGFloat screenScale = [[UIScreen mainScreen] scale];
    CGSize screenSize = CGSizeMake(screenBounds.size.width * screenScale, screenBounds.size.height * screenScale);

    UIGraphicsBeginImageContext(screenSize);
    [image drawInRect:CGRectMake(0,0,screenSize.width,screenSize.height)];
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults];
    [currentDefaults setObject:UIImagePNGRepresentation(newImage) forKey:@"newImageKey"];
    [currentDefaults synchronize];

    [popoverController dismissPopoverAnimated:YES];
    [picker dismissModalViewControllerAnimated:YES];
}

有没有办法更快地调整大小或以其他方式执行此操作，以便在系统调整大图像大小时用户不会注意到延迟？

谢谢！

Answer 1

一般来说，我建议你做两件事。首先，考虑使用块来使调整大小和保存操作发生在主线程之外（这需要iOS 4.0及更高版本）。你的方法看起来像这样（在我的头顶而不是编译）

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    CGRect screenBounds = [[UIScreen mainScreen] bounds];
    CGFloat screenScale = [[UIScreen mainScreen] scale];
    CGSize screenSize = CGSizeMake(screenBounds.size.width * screenScale, screenBounds.size.height * screenScale);

    UIGraphicsBeginImageContext(screenSize);
    [image drawInRect:CGRectMake(0,0,screenSize.width,screenSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults];
    [currentDefaults setObject:UIImagePNGRepresentation(newImage) forKey:@"newImageKey"];
    [currentDefaults synchronize];
});

[popoverController dismissPopoverAnimated:YES];
[picker dismissModalViewControllerAnimated:YES];
}

我强烈建议的第二件事是不将结果图像存储在NSUserDefaults中。 NSUserDefaults仅用于小型键值存储。如果要存储图像，请使用NSFileManager将它们存储在磁盘上，并将路径存储为NSUserDefaults中的值。

调整UIImage的大小需要很长时间？

1 个答案: