Question

所以我有一个函数从URL获取图像，如下所示：

- (UIImage *) getImageFromURL:(NSString *)fileURL {
    UIImage * result;

    NSData * img_data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
    result = [UIImage imageWithData:img_data];

    return result;
}

然后是一个从UIImage中保存图像的函数，如下所示：

    -(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    if ([[extension lowercaseString] isEqualToString:@"png"]) {
        [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
    } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
        [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
        NSLog(@"Image named %@ wrote to %@", imageName, directoryPath);
    } else {
        NSLog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
    }
}

我面临的问题是，当我通过saveImage函数运行UIImage时，我认为它不会保存图像。这是因为当我检查UIImage imageNamed：@“Documents / filenamesavedas.jpeg”时，它返回（null）。但是图像可以正确下载。

这是我的文档目录路径功能：

- (NSString *)getDocumentsDirectoryPath {
    NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSLog(documentsDirectoryPath);
    return documentsDirectoryPath;
}

以下是我下载并尝试保存图片的位置：

   dispatch_async(jsonQueue, ^{
        // check to see if data authenticate runs successfully. 
    NSString *documentsDirectoryPath = [util getDocumentsDirectoryPath];
    UIImage *imageToSave = [util getImageFromURL:[properties objectForKey:@"current_group_logoURL"]];
    [util saveImage:imageToSave withFileName:[properties objectForKey:@"home_venue_logo"] ofType:@"jpeg" inDirectory:documentsDirectoryPath];
    NSLog(@"Group Logo URL %@", [properties objectForKey:@"current_group_logoURL"]);
    NSLog(@"Current Group Image %@", [properties objectForKey:@"home_venue_logo"]);        
        UIImage *testToSeeItHasDownloaded = imageToSave;
        NSString *imageLocation = [documentsDirectoryPath stringByAppendingPathComponent:[properties objectForKey:@"home_venue_logo"]];
        NSData *data = [NSData dataWithContentsOfFile:imageLocation];
        UIImage *testToSeeImageHasSaved = [UIImage imageWithData:data];
        NSLog(@"testToSeeImagehasDownloaded: %@", testToSeeItHasDownloaded);
        NSLog(@"image location to save to: %@", imageLocation);
        NSLog(@"testToSeeImagehasSaved: %@", testToSeeImageHasSaved );    

    });

控制台返回：

2012-10-22 16:27:45.642 asdaf[46819:1d807] Group Logo URL http://somesite.com/50a0e42619424ba551a956511c098656.jpeg
2012-10-22 16:27:45.642 asdaf[46819:1d807] Current Group Image 50a0e42619424ba551a956511c098656.jpeg
2012-10-22 16:27:45.649 asdaf[46819:1d807] testToSeeImagehasDownloaded: <UIImage: 0xb09ed50>
2012-10-22 16:27:45.649 asdaf[46819:1d807] testToSeeImagehasSaved: (null)

testToSeeImagehasSaved应该返回null。但是我做错了什么？谢谢。

Answer 1

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
//documentsDirectory is your documents directory path

//Now append your image name in this path
NSString *imagePath = [documentsDirectory stringByAppendingPathComponent:@"ImageName.jpeg"];

//convert your image in NSData
NSData *imageData = UIImagePNGRepresentation(image);
//Now write it at path
[imageData writeToFile:imagePath atomically:NO];

您可以采用相同的方式获取此图片

NSData *data = [NSData dataWithContentsOfFile:imagePath];
UIImage *image = [UIImage imageWithData:data];

修改

-(void)saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *imageName = [imageName stringByAppendingString:extension]; //Note extension should be like .png, .jpg, .jpeg dont forget dot (.). NSString *imagePath = [documentsDirectory stringByAppendingPathComponent:imageName]; NSData *imageData = UIImagePNGRepresentation(image); [imageData writeToFile:imagePath atomically:NO]; }

我现在还不知道您的整个代码，但是当您必须将图像保存在文档目录中时，为什么要传递UIImage对象。您也可以在方法中传递NSData。你做得更多。

你的问题是你每次都在保存.jpg图像，并且在检索时你试图在相同的路径上找到.jpeg图像，这就是你获得空值的原因。请在保存方法中查看此行 -

[UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];

Answer 2

这条线看起来不对我：

UIImage *testToSeeImageHasSaved = [UIImage imageNamed: [@"Documents/" stringByAppendingString: [properties objectForKey:@"home_venue_logo"]]];

我认为你必须这样做：

UIImage* image = [UIImage imageWithContentsOfFile:"YOUR_FILE_PATH"];

[UIImage imageNamed:"image_name"]仅适用于附加到项目中的图片

Answer 3

当您将其保存在文档文件夹中时，它不会将其保存在“文档”目录中，而是将其保存在

中

path=/var/mobile/Applications/144B3628-5258-4939-8B80-006EC5BE45B2/Library/Caches/6_1.png

因此要恢复图像，您应该使用

NSString *uniquePath = [directory stringByAppendingPathComponent: filename];
image = [UIImage imageWithContentsOfFile: uniquePath];

其中directory是用于保存它的路径，文件名是jpeg的名称。

Answer 4

[UIImage imageNamed:@"Documents/filenamesavedas.jpeg"]

没有路径它会搜索你的包中有特定名称的文件。

使用对NSFileManager的调用找到该文件，并使用预期的路径和文件名。

试图将jpeg保存到app的Documents目录

4 个答案:

试图将jpeg保存到a​​pp的Documents目录

4 个答案:

试图将jpeg保存到app的Documents目录