尝试 addImage:forDuration:withAttributes 时 QTMovie 索引出界异常

Question

我正在尝试使用 QTKit 在 Cocoa 中创建一部电影。这部电影应该由我创建的一堆 NSImage 组成。我遇到了一些问题。总体问题是这部电影没有制作出来。我得到一个看起来是空的文件，只包含几百个字节，但没有电影可言。不管怎样，代码是：

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    NSLog(@"Creating .mov out of NSImage(s)");

    NSError *error = nil;

    // Create empty QTMovie with writable data reference
    QTMovie *movie = [[QTMovie alloc] initToWritableFile:@"Temp.mov" error:&error];

    // If an error occurred, print it
    if ( error )
        NSLog(@"Error creating movie: %@", [error localizedDescription]);

    // Sanity-check to see that our movie is writable
    assert([[movie attributeForKey:QTMovieEditableAttribute] boolValue] == YES);

    // Load our image
    NSImage *image = [NSImage imageNamed:@"screen-1"];

    // Check that our image is loaded
    assert(image != nil);

    // Add the image to our movie, duration is 6000 / 600 = 10 seconds?
    NSDictionary *attributesForImage = [NSDictionary dictionaryWithObjectsAndKeys:@"tiff", QTAddImageCodecType, nil];
    [movie addImage:image forDuration:QTMakeTime(6000, 600) withAttributes:attributesForImage];

    // Store our movie in a file called "Done.mov"
    // flattening it seems like a good idea
    NSDictionary *attributesForExport = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],
                                QTMovieFlatten, nil];
    error = nil;
    BOOL didSucceed = [movie writeToFile:@"Done.mov" withAttributes:attributesForExport error:&error];

    if ( ! didSucceed || error )
        NSLog(@"Did not succeed. Error was: %@", [error localizedDescription]);
    else
    {
        // If we did succeed, error should be nil, right?
        assert(error == nil);

        NSLog(@"Did succeed.");
    }

    // Cleanup
    [movie release];
    [[NSFileManager defaultManager] removeItemAtPath:@"Temp.mov" error:nil];
    [NSApp terminate:nil];
}

需要关注的行是[movie addImage...。这就是错误发生的地方。我得到以下例外：

eException', reason: '*** -[NSArray objectAtIndex:]: index (0) beyond bounds (0)'
*** Call stack at first throw:
(
0   CoreFoundation                      0x90e806ba __raiseError + 410
1   libobjc.A.dylib                     0x97cde509 objc_exception_throw + 56
2   CoreFoundation                      0x90ec5321 -[__NSArray0 objectAtIndex:] + 209
3   QTKit                               0x9387492c -[QTMovie_QuickTime addImage:forDuration:atTime:withAttributes:] + 708
4   QTKitServer                         0x000208ba do_addImageAtTimeWithAttributes + 327
5   QTKitServer                         0x0000cb03 _XaddImageAtTimeWithAttributes + 291
6   QTKitServer                         0x000021bb QTKitServer_server + 113
7   QTKitServer                         0x0001e194 mach_port_callback + 84
8   CoreFoundation                      0x90dee772 __CFMachPortPerform + 338
9   CoreFoundation                      0x90dea4db __CFRunLoopRun + 6523
10  CoreFoundation                      0x90de8464 CFRunLoopRunSpecific + 452
11  CoreFoundation                      0x90dee3a4 CFRunLoopRun + 84
12  QTKitServer                         0x0001e702 main + 1068
13  QTKitServer                         0x00002141 start + 53
)

我用谷歌搜索了很多，但没有找到真正回答这个问题的东西。该代码非常简单，它看起来与大多数代码示例完全相同。图像加载正常，但根本没有添加。有什么想法吗？如果相关的话，它是一个 JPEG 图像。

Answer 1

你的代码没问题。 [NSImage imageNamed:] 返回的 NSImage 实例似乎存在问题。
尝试将该行替换为（假设您的图像已复制到捆绑包的资源文件夹中）：

NSString* imagePath = [[[NSBundle mainBundle] resourcePath]     
                      stringByAppendingPathComponent:@"screen-1.jpg"];
NSImage* image = [[NSImage alloc] initWithContentsOfFile:imagePath];

将其添加到电影后，不要忘记添加 [image release] 。