在将图像数组转换为视频时裁剪图像

Question

在我的应用程序中，我将图像数组转换为视频。为此，我正在使用以下代码。

NSFileManager *fileMgr = [NSFileManager defaultManager];
    NSString *documentsDirectory = [NSHomeDirectory()
                                    stringByAppendingPathComponent:@"Documents"];
    NSString *videoOutputPath = [documentsDirectory stringByAppendingPathComponent:@"test_output.mp4"];
    //NSLog(@"-->videoOutputPath= %@", videoOutputPath);
    // get rid of existing mp4 if exists...
    if ([fileMgr removeItemAtPath:videoOutputPath error:&error] != YES)
        NSLog(@"Unable to delete file: %@", [error localizedDescription]);

    NSUInteger fps = 30;


    //////////////     end setup    ///////////////////////////////////

    NSLog(@"Start building video from defined frames.");

    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
                                  [NSURL fileURLWithPath:videoOutputPath] fileType:AVFileTypeQuickTimeMovie
                                                              error:&error];
    NSParameterAssert(videoWriter);

    NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:288], AVVideoWidthKey,
                                   [NSNumber numberWithInt:352], AVVideoHeightKey,
                                   nil];

    AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
                                            assetWriterInputWithMediaType:AVMediaTypeVideo
                                            outputSettings:videoSettings];


    AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                     assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput
                                                     sourcePixelBufferAttributes:nil];

    NSParameterAssert(videoWriterInput);
    NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
    videoWriterInput.expectsMediaDataInRealTime = YES;
    [videoWriter addInput:videoWriterInput];

    //Start a session:
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];

    CVPixelBufferRef buffer = NULL;


    //convert uiimage to CGImage.
    int frameCount = 0;


    //for(VideoFrame * frm in imageArray)
    NSLog(@"**************************************************");
    for(UIImage * img in finalArrayVal)
    {
        //UIImage * img = frm._imageFrame;
        buffer = [self pixelBufferFromCGImage:[img CGImage]];

        BOOL append_ok = NO;
        int j = 0;
        while (!append_ok && j < 30) {
            if (adaptor.assetWriterInput.readyForMoreMediaData)  {
                //print out status:
                NSLog(@"Processing video frame (%d,%lu)",frameCount,(unsigned long)[finalArrayVal count]);

                CMTime frameTime = CMTimeMake(frameCount,(int32_t) fps);
                append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
                if(!append_ok){
                    NSError *error = videoWriter.error;
                    if(error!=nil) {
                        NSLog(@"Unresolved error %@,%@.", error, [error userInfo]);
                    }
                }
            }
            else {
                printf("adaptor not ready %d, %d\n", frameCount, j);
                [NSThread sleepForTimeInterval:0.1];
            }
            j++;
        }
        if (!append_ok) {
            printf("error appending image %d times %d\n, with error.", frameCount, j);
        }
        frameCount++;
    }
    NSLog(@"**************************************************");

    //Finish the session:
    [videoWriterInput markAsFinished];
    [videoWriter finishWriting];

它将图像数组转换为视频文件。但是当我尝试将其转换为视频时，它会像下面一样裁剪图像的一部分。

输入图像：

输出视频截图：

您可以看到图像的上部被高度忽略。请注意，我已在相机中为 defaultAVCaptureSessionPreset 设置了 AVCaptureSessionPreset352x288。在这里，我需要将完整图像转换为视频中的帧。谁能提供解决上述问题的解决方案。

Answer 1

研究后，我替换了下面的行以发送附加参数（图像大小）

 buffer = [myController pixelBufferFromImage:[img CGImage] andSize:imageSize];

而不是这个：

buffer = [self pixelBufferFromCGImage:[img CGImage]];

并在myController中添加了这个方法

+ (CVPixelBufferRef) pixelBufferFromImage: (CGImageRef) image andSize:(CGSize) size
{
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,nil];
    CVPixelBufferRef pxbuffer = NULL;
    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, size.width,
                                          size.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,&pxbuffer);
    NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);
    CVPixelBufferLockBaseAddress(pxbuffer, 0);
    void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
    NSParameterAssert(pxdata != NULL);
    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pxdata, size.width,
                                                 size.height, 8, 4*size.width, rgbColorSpace,
                                                 kCGImageAlphaNoneSkipFirst);
    NSParameterAssert(context);
    CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image),
                                           CGImageGetHeight(image)), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);
    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
    return pxbuffer;
}