从(到)“选择的"获取 URL图像，iOS [英] Getting a URL from (to) a "picked" image, iOS

问题描述

使用下面的代码，我可以从图像中提取元数据(预先添加到我的项目中)，并将信息呈现为文本.这正是我想要做的.SYMetadata 是通过 URL 指向图像创建的.initWithAbsolutePathURL.我想对 UIImage 或者正在加载到 UIImage 的图像做同样的事情.如何获取选择器选择的图像的 URL?或者我如何从这个传入的图像创建一个资产"?

With this code below, I can extract metadata from an image (pre-added to my project), and render the info as text. This is exactly what I want to do. The SYMetadata is created by pointing to an image via URL. initWithAbsolutePathURL. I want to do the same thing with a UIImage or maybe the image that is being loaded to the UIImage. How do I get the URL to the image that the picker selects? Or how do I create an "asset" from this incoming image?

文档描述了initWithAsset.还没有想出如何使用它，或者这是否是达到我目的的正确方法.非常感谢任何帮助.

The documentation describes initWithAsset. Have not figured out how to use it yet though, or if this is the right way to go for my purpose. Any help greatly appreciated.

NSURL *imageURL = [[NSBundle mainBundle] URLForResource:@"someImage" withExtension:@"jpg"];
SYMetadata *metadata = [[SYMetadata alloc] initWithAbsolutePathURL:imageURL];
[textView setText:[[metadata allMetadatas] description]];

注意:我尝试在pickerDidFinish"方法中添加这样的 NSURL imageURL = [info valueForKey:@"UIImagePickerControllerReferenceURL"];，但元数据为空在我将这个 URL 添加到上面的代码之后.

Note: I tried adding an NSURL like this imageURL = [info valueForKey:@"UIImagePickerControllerReferenceURL"];, in the "pickerDidFinish" method but the metadata is null after I add this URL to the above code.

推荐答案

如果你使用的是 imagePickerController，delegate 方法会给你你所需要的

If you are using the imagePickerController, the delegate method will give you what you need

- (void) imagePickerController:(UIImagePickerController *)picker
 didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    if ([[info allKeys] containsObject:UIImagePickerControllerReferenceURL]){
        // you will get this key if your image comes from a library
        [self setMetaDataFromAssetLibrary:info];
    } else if ([[info allKeys] containsObject:UIImagePickerControllerMediaMetadata]){
        // if the image comes from the camera you get the metadata in it's own key
        self.rawMetaData = [self metaDataFromCamera:info];
    }
}

来自资产库 - 请记住，完成需要时间并且具有异步完成块，因此您可能需要添加完成标志以确保在更新之前您不会访问该属性.

From Asset Library - bear in mind that it takes time to complete and has an asynchronous completion block, so you might want to add a completion flag to ensure you don't access the property before it has been updated.

- (void) setMetaDataFromAssetLibrary:(NSDictionary*)info
{
    NSURL *assetURL = [info objectForKey:UIImagePickerControllerReferenceURL];

    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [library assetForURL:assetURL
             resultBlock:^(ALAsset *asset)  {
                 self.rawMetaData = asset.defaultRepresentation.metadata;
             }
            failureBlock:^(NSError *error) {
                NSLog (@"error %@",error);
            }];
}

来自相机:

    - (NSDictionary*)metaDataFromCamera:(NSDictionary*)info
   {
        NSMutableDictionary *imageMetadata = [info objectForKey:UIImagePickerControllerMediaMetadata];
       return imageMetadata;
   }

这里是如何从 UIImage 获取元数据

Here is how to get metadata from a UIImage

  - (NSDictionary*)metaDataFromImage:(UIImage*)image
   {
        NSData *jpegData = [NSData dataWithData:UIImageJPEGRepresentation(image, 1.0)];
        return [self metaDataFromData:jpegData];
    }

但请注意 - UIImage 已经可以从原始数据中剥离大部分元数据......你最好从用于创建 UIImage 的 NSData 中获取元数据......

But take care - a UIImage can already stripped of much of the metadata from the original.. you will be better off getting the metadata from the NSData that was used to create the UIImage...

    - (NSDictionary*)metaDataFromData:(NSData*)data
{
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
    CFDictionaryRef imageMetaData = CGImageSourceCopyPropertiesAtIndex(source,0,NULL);
    return (__bridge NSDictionary *)(imageMetaData);
}

这篇关于从(到)“选择的"获取 URL图像，iOS的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！