本文将带你了解iOS开发之CGAffineTransform  视频旋转，希望本文对大家学IOS有所帮助。

  
  
  
   记录下视频旋转

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- (void)test:(NSURL *)url transformUrl:(NSURL *)exportUrl {
[self rotateVideoAssetWithFileURL:url dstFileURL:exportUrl];
}

- (void)rotateVideoAssetWithFileURL:(NSURL *)fileURL dstFileURL:(NSURL *)dstFileURL {
    
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], AVURLAssetPreferPreciseDurationAndTimingKey, nil];
    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:fileURL options:options];
    
    AVAssetTrack *videoAssetTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    AVAssetTrack *audioAssetTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    if (videoAssetTrack == nil || audioAssetTrack == nil) {
        NSLog(@"error is %@", @"video or audio assetTrack is nil");
        return;
    }
    
    AVMutableVideoComposition* videoComposition = [AVMutableVideoComposition videoComposition];
    videoComposition.frameDuration = videoAssetTrack.minFrameDuration;
    CGSize renderSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
    videoComposition.renderSize = renderSize;
    
    //create a video instruction
    AVMutableVideoCompositionInstruction *videoCompositionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    videoCompositionInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);
    
    AVMutableVideoCompositionLayerInstruction *videoCompositionLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoAssetTrack];
    
    //仿射变换的坐标为iOS的屏幕坐标x向右为正y向下为正
    CGAffineTransform transform = [self videoAssetTrackTransform:videoAssetTrack];
    [videoCompositionLayerInstruction setTransform:transform atTime:kCMTimeZero];
    
    //add the transformer layer instructions, then add to video composition
    videoCompositionInstruction.layerInstructions = [NSArray arrayWithObject:videoCompositionLayerInstruction];
    videoComposition.instructions = [NSArray arrayWithObject: videoCompositionInstruction];
    
    AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];
#warning when use (not AVAssetExportPresetPassthrough) AVAssetExportSession export video which is contain video and audio must add video track first,
#warning when add audio track frist error is -11841.
    AVMutableCompositionTrack *videoCompositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    NSError *error = nil;
    [videoCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:videoAssetTrack atTime:kCMTimeZero error:&error];
    if (error) {
        NSLog(@"error is %@", error);
        return;
    }
    error = nil;
    AVMutableCompositionTrack *audioCompositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    [audioCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:audioAssetTrack atTime:kCMTimeZero error:&error];
    if (error) {
        NSLog(@"error is %@", error);
        return;
    }
    NSLog(@"the assetDuration is %lld", asset.duration.value/asset.duration.timescale);
    
    AVAssetExportSession *assetExportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality] ;
    assetExportSession.shouldOptimizeForNetworkUse = YES;
    assetExportSession.videoComposition = videoComposition;
    assetExportSession.outputURL = dstFileURL;
    assetExportSession.outputFileType = AVFileTypeMPEG4;
    
    __weak AVAssetExportSession *weakAssetExportSession = assetExportSession;
    __weak typeof(self)weakSelf = self;
    [assetExportSession exportAsynchronouslyWithCompletionHandler:^
     {
         if ([weakAssetExportSession status] != AVAssetExportSessionStatusCompleted) {
             NSLog(@"the error is %@", [weakAssetExportSession error]);
             NSLog(@"the status is %ld", (long)[weakAssetExportSession status]);
             NSLog(@"the outPutPath is %@", [weakAssetExportSession.outputURL absoluteString]);
             NSLog(@"the error is %@", [weakAssetExportSession error].userInfo);
         }
         dispatch_async(dispatch_get_main_queue(), ^{
#warning here can not use weakAssetExportSession.outputURL weakAssetExportSession.outputURL some time is null but video is exit.
             [weakSelf exportDidFinish:dstFileURL];
         });
     }];
}

- (CGAffineTransform)videoAssetTrackTransform:(AVAssetTrack *)videoAssetTrack {
    int degrees = -180;//[self degressFromVideoFileWithVideoAssetTrack:videoAssetTrack];
    CGAffineTransform transform = CGAffineTransformIdentity;
    if (degrees != 0) {
        CGAffineTransform translateToCenter = CGAffineTransformIdentity;
        if (degrees == 90) {
            // 顺时针旋转90°
            translateToCenter = CGAffineTransformMakeTranslation(videoAssetTrack.naturalSize.height, 0.0);
            transform = CGAffineTransformRotate(translateToCenter, M_PI_2);
        } else if(degrees == 180){
            // 顺时针旋转180°
            translateToCenter = CGAffineTransformMakeTranslation(videoAssetTrack.naturalSize.width, videoAssetTrack.naturalSize.height);
            transform = CGAffineTransformRotate(translateToCenter, M_PI);
        } else if(degrees == 270){
            // 顺时针旋转270°
            translateToCenter = CGAffineTransformMakeTranslation(0.0, videoAssetTrack.naturalSize.width);
            transform = CGAffineTransformRotate(translateToCenter, M_PI_2 + M_PI);
        }else if(degrees == -180){
            // 绕x轴旋转180度
            //仿射变换的坐标为iOS的屏幕坐标x向右为正y向下为正
#if 1
//            transform = CGAffineTransformTranslate(transform, videoAssetTrack.naturalSize.width, videoAssetTrack.naturalSize.height);
            //transform = CGAffineTransformRotate(transform, 90/180.0f*M_PI); // 旋转90度
            //transform = CGAffineTransformScale(transform, 1.0, -1.0); // 上下颠倒视频
            
//            translateToCenter = CGAffineTransformMakeTranslation(videoAssetTrack.naturalSize.height, 0.0);
//            transform = CGAffineTransformRotate(translateToCenter, -M_PI_2);
            
            transform = CGAffineTransformScale(transform, -1.0, 1.0);  // 左右颠倒视频
            transform = CGAffineTransformTranslate(transform, -videoAssetTrack.naturalSize.width, 0);
//            transform = CGAffineTransformRotate(translateToCenter, -M_PI_2);

            //transform = CGAffineTransformScale(transform, 1.0, 1.0); // 使用原始大小
            
            //原始视频
            //         ___
            //        |   |
            //        |   |
            //     -------------------- +x
            //    |
            //    |
            //    |
            //    |
            //    |
            //    |
            //    |
            //    +y
            
            //transform = CGAffineTransformScale(transform, 1.0, -1.0); // 上下颠倒视频
            
            //     -------------------- +x
            //    |   |   |
            //    |   |___|
            //    |
            //    |
            //    |
            //    |
            //    |
            //    +y
            
            //transform = CGAffineTransformTranslate(transform, 0, -videoAssetTrack.naturalSize.height);// 将视频平移到原始位置
            
            //         ___
            //        |   |
            //        |   |
            //     -------------------- +x
            //    |
            //    |
            //    |
            //    |
            //    |
            //    |
            //    |
            //    +y
            
//            transform = CGAffineTransformScale(transform, 1.0, -1.0); // 上下颠倒视频
//            transform = CGAffineTransformTranslate(transform, 0, -videoAssetTrack.naturalSize.height);
#else
            transform = videoAssetTrack.preferredTransform;
            transform = CGAffineTransformTranslate(transform, 0, -videoAssetTrack.naturalSize.height);
#endif
        }
    }
    
#if 0 - cropVideo
    //Here we shift the viewing square up to the TOP of the video so we only see the top
    CGAffineTransform t1 = CGAffineTransformMakeTranslation(videoAssetTrack.naturalSize.height, 0 );
    
    //Use this code if you want the viewing square to be in the middle of the video
    //CGAffineTransform t1 = CGAffineTransformMakeTranslation(videoAssetTrack.naturalSize.height, -(videoAssetTrack.naturalSize.width - videoAssetTrack.naturalSize.height) /2 );
    
    //Make sure the square is portrait
    transform = CGAffineTransformRotate(t1, M_PI_2);
#endif
    
    return transform;
}

- (int)degressFromVideoFileWithVideoAssetTrack:(AVAssetTrack *)videoAssetTrack {
    int degress = 0;
    CGAffineTransform t = videoAssetTrack.preferredTransform;
    if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0){
        // Portrait
        degress = 90;
    } else if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0){
        // PortraitUpsideDown
        degress = 270;
    } else if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0){
        // LandscapeRight
        degress = 0;
    } else if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0){
        // LandscapeLeft
        degress = 180;
    } else if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0){
        // LandscapeLeft
        degress = 180;
    } else if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == -1.0){
        // x-axis
        degress = -180;
    }
    
    return degress;
}

- (void)exportDidFinish:(NSURL *)fileURL {
    NSLog(@"fileURL is %@", fileURL);    
    
     dispatch_async(dispatch_get_main_queue(), ^{
     
     if ([XCFileManager isExistsAtPath:[self.videoUrl path]]) {
     
     
     NSURL *outputURL = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:@"temp.mov"]];
     
     [self convertVideoToLowQuailtyWithInputURL:fileURL outputURL:outputURL handler:^(AVAssetExportSession *exportSession)
     {
     dispatch_async(dispatch_get_main_queue(), ^{
     self.recordState = FMRecordStateFinish;
     });
     
     if (exportSession.status == AVAssetExportSessionStatusCompleted) {
     
     self.videoUrl = outputURL;
     self.videoFirstImage = firstImage;
     
     }else {
     printf("error\n");
     }
     }];
     
     
     }
     
     });
     
}

   

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