ios - 如何从视频中提取图像？

Question

谁能告诉我如何从视频中提取图像？到目前为止，我一直在尝试遵循这些:

• Getting iPhone video thumbnails
• Getting a thumbnail from a video url or data in iPhone SDK
• How do I extract a screenshot from a video in the iPhone SDK?
• iPhone Read UIimage (frames) from video with AVFoundation , iphone sdk > 3.0 . Video Thumbnail?

等之后我做了这个:

源代码:

- (void)viewDidLoad
{
    videoPicker = [[UIImagePickerController alloc] init];
    [videoPicker setDelegate:self];
    videoPicker.sourceType =  UIImagePickerControllerSourceTypePhotoLibrary;
    NSArray *mediaTypesAllowed = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
    videoPicker.mediaTypes = mediaTypesAllowed;
    videoPicker.view.hidden = YES;
}


-(IBAction)imgPickerController
{
    [self presentModalViewController:videoPicker animated:YES];
    videoPicker.view.hidden = NO;
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    // e.g.
    NSString *tempFilePath = [(NSURL *)[info valueForKey:UIImagePickerControllerMediaURL] absoluteString];

    NSLog(@"didFinishPickingMediaWithInfo: %@",tempFilePath);

    // e.g. /private/var/mobile/Applications/D1E784A4-EC1A-402B-81BF-F36D3A08A332/tmp/capture/capturedvideo.MOV
    tempFilePath = [tempFilePath substringFromIndex:16];

    NSLog(@"didFinishPickingMediaWithInfo: %@",tempFilePath);
    NSLog(@"===Try to save video to camera roll.===");
    NSLog(@"UIVideoAtPathIsCompatibleWithSavedPhotosAlbum: %@",UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(tempFilePath)? @"YES":@"NO");

    // Check if the video file can be saved to camera roll.
    if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(tempFilePath))
    {
        // YES. Copy it to the camera roll.
        UISaveVideoAtPathToSavedPhotosAlbum(tempFilePath, self, @selector(video:didFinishSavingWithError:contextInfo:),(__bridge_retained void *)tempFilePath );
    }

    [self dismissModalViewControllerAnimated:YES];
}

- (void)video:(NSString *)videoPath didFinishSavingWithError:(NSError *)error contextInfo:(NSString *)contextInfo
{
    NSLog(@"didFinishSavingWithError--videoPath in camera roll:%@",videoPath);
    NSLog(@"didFinishSavingWithError--videoPath in temp directory:%@",contextInfo);

    // The thumbnail jpg should located in this directory.
    NSString *thumbnailDirectory = [[contextInfo stringByDeletingLastPathComponent] stringByDeletingLastPathComponent];

    // Debug info. list all files in the directory of the video file.
    // e.g. /private/var/mobile/Applications/D1E784A4-EC1A-402B-81BF-F36D3A08A332/tmp/capture
    NSLog(@"%@",[contextInfo stringByDeletingLastPathComponent]);
    NSLog(@"%@",[[[NSFileManager defaultManager] contentsOfDirectoryAtPath:[contextInfo stringByDeletingLastPathComponent] error:nil] description]);

    // Debug info. list all files in the parent directory of the video file, i.e. the "~/tmp" directory.
    // e.g. /private/var/mobile/Applications/D1E784A4-EC1A-402B-81BF-F36D3A08A332/tmp
    NSLog(@"%@",thumbnailDirectory);
    NSLog(@"%@",[[[NSFileManager defaultManager] contentsOfDirectoryAtPath:thumbnailDirectory error:nil] description]);
    ///////////////////

    // Find the thumbnail for the video just recorded.
    NSString *file,*latestFile;

    NSDate *latestDate = [NSDate distantPast];
    NSDirectoryEnumerator *dirEnum = [[NSFileManager defaultManager] enumeratorAtPath:[[contextInfo stringByDeletingLastPathComponent]stringByDeletingLastPathComponent]];

    // Enumerate all files in the ~/tmp directory
    while (file = [dirEnum nextObject])
    {
        // Only check files with jpg extension.
        if ([[file pathExtension] isEqualToString: @"jpg"]) 
        {
            NSLog(@"***latestDate:%@",latestDate);
            NSLog(@"***file name:%@",file);
            NSLog(@"***NSFileSize:%@", [[dirEnum fileAttributes] valueForKey:@"NSFileSize"]);
            NSLog(@"***NSFileModificationDate:%@", [[dirEnum fileAttributes] valueForKey:@"NSFileModificationDate"]);

            // Check if current jpg file is the latest one.
            if ([(NSDate *)[[dirEnum fileAttributes] valueForKey:@"NSFileModificationDate"] compare:latestDate] == NSOrderedDescending)
            {
                latestDate = [[dirEnum fileAttributes] valueForKey:@"NSFileModificationDate"];
                latestFile = file;
                NSLog(@"***latestFile changed:%@",latestFile);
            }
        }
    }

    // The thumbnail path.
    latestFile = [NSTemporaryDirectory() stringByAppendingPathComponent:latestFile];
    NSLog(@"****** The thumbnail file should be this one:%@",latestFile);

    UIImage *img = [[UIImage alloc] initWithContentsOfFile:latestFile];
    UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(150, 150, 100, 100)];
    [imgView setImage:img];
    imgView.layer.borderWidth = 2.0;
    [self.view addSubview:imgView];

    // Your code ...
    // Your code ...
    // Your code ...
}

在完成所有这些之后，我仍然无法到达我想到达的地方。我仍然无法获取图像。我现在被卡住了。请有人帮助我!!!谢谢 :)

Answer 1

从电影中提取缩略图的简单方法是使用 MPMoviePlayerController 类及其 - thumbnailImageAtTime:timeOption: 方法。

例如，您有一个文件路径 url:

NSURL *tempFilePathURL = ...;
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL: tempFilePathURL];
UIImage *thumbnail = [player thumbnailImageAtTime:THUMBNAIL_TIME timeOption:MPMovieTimeOptionExact];
[player release];

我在我的代码中使用了它并且它有效。