iOS图片，视频上传视频内容旋转

#前言
我最近在接手一个智能盒子的iOS应用，上面有一个功能是这样的。把你本地的照片和视频可以甩屏到你绑定的盒子上。
我的上一位前辈做的时候必须要求再同一个局域网，但是当我做的时候要求不同的局域网也要实现这样的一个功能，优化用户的使用感受。

#那么 我们下面就进入正题。

#内容一：图片上传
我做的图片上传是用的AF，原理就是把你想上传的照片取出来，如果有文件大小的要求就先做相应的图片压缩。
然后用AFHTTPSessionManager 类去做的上传，下面就是代码：

AFHTTPSessionManager *session = [AFHTTPSessionManager manager];[session.requestSerializer willChangeValueForKey:@"timeoutInterval"];session.requestSerializer.timeoutInterval = 60.f;[session.requestSerializer didChangeValueForKey:@"timeoutInterval"];session.responseSerializer = [AFHTTPResponseSerializer serializer];NSString *imageTitle =_imageSource[pageIndex].title;imageTitle = [imageTitle substringToIndex:imageTitle.length-4];NSDictionary *params = @{@"fileType":@"jpg",@"fileName":imageTitle};[session POST:@"你上传的接口地址" parameters:params constructingBodyWithBlock:^(id<AFMultipartFormData>  _Nonnull formData) {for (NSString *key in dict.allKeys) {[formData appendPartWithFileData:[dict objectForKey:key] name:@"myFile" fileName:[NSString stringWithFormat:@"%@.jpg",key] mimeType:@"image/jpeg"];}} progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {}];

这里主要就是和你们的后台确认好相应的参数设置就好了。

#内容二：视频上传
视频上传和图片上传其实是类似的，只不过就是参数的设置不一样而已。也是用上面的方法。关键也是设置好参数。
在这里我想说的是，有的时候视频太大要做相应的压缩处理。因为我之前对视频这面接触的比较少，也上网找了一些资料然后看到这样的一个方法：

- (void)lowQuailtyWithInputURL:(NSURL*)inputURLoutputURL:(NSURL*)outputURLblockHandler:(void (^)(AVAssetExportSession*))handler
{
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];AVAssetExportSession *session = [[AVAssetExportSession alloc] initWithAsset:asset     presetName:AVAssetExportPresetMediumQuality];session.outputURL = outputURL;session.outputFileType = AVFileTypeQuickTimeMovie;[session exportAsynchronouslyWithCompletionHandler:^(void){handler(session);}];
}

通过这个方法就可以对视频进行相应的压缩处理。

#下面就是视频内容的旋转问题了。
一开始我听到了这个需求的时候我的脑子里真的是瞬间万马飞奔啊！！ 这是什么鬼需求啊！鬼知道我经历了什么？
我想，那我就上网找一下吧！我找了一下，还真的有这么样的技术博客。但是一上来就是把他的代码网上一贴。我先大概的浏览了一下那代码的长度。写的我实在是没有耐心去仔细的看到底是怎么实现的。我就关掉了。可是后来一看，也没有别的什么博客供我参考了。在我走投无路的时候，我看到了这么一个博客，说是Apple自己就有Demo，我就抱着好奇的态度去看了看。下载了那个Demo仔细的研究了一下。果然就好使了。 那么，接下来就说一下。

再旋转视频之前我们先要确认一下，这个视频是要旋转多少度。

 AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];NSInteger degress;if([tracks count] > 0) {AVAssetTrack *videoTrack = [tracks objectAtIndex:0];CGAffineTransform t = videoTrack.preferredTransform;//这里的矩阵有旋转角度，转换一下即可if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0){// Portraitdegress = 90;}else if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0){// PortraitUpsideDowndegress = 270;}else if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0){// LandscapeRightdegress = 0;}else if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0){// LandscapeLeftdegress = 180;}}

这样我们就可以通过degress来确认旋转的角度了。
那么我们接下来就开始旋转视频

AVMutableVideoCompositionInstruction *instruction = nil;AVMutableVideoCompositionLayerInstruction *layerInstruction = nil;CGAffineTransform t1;CGAffineTransform t2;AVAssetTrack *assetVideoTrack = nil;AVAssetTrack *assetAudioTrack = nil;// Check if the asset contains video and audio tracksif ([[asset tracksWithMediaType:AVMediaTypeVideo] count] != 0) {assetVideoTrack = [asset tracksWithMediaType:AVMediaTypeVideo][0];}if ([[asset tracksWithMediaType:AVMediaTypeAudio] count] != 0) {assetAudioTrack = [asset tracksWithMediaType:AVMediaTypeAudio][0];}CMTime insertionPoint = kCMTimeZero;NSError *error = nil;// Step 1// Create a composition with the given asset and insert audio and video tracks into it from the assetif (!mutableComposition) {// Check whether a composition has already been created, i.e, some other tool has already been applied// Create a new compositionmutableComposition = [AVMutableComposition composition];// Insert the video and audio tracks from AVAssetif (assetVideoTrack != nil) {AVMutableCompositionTrack *compositionVideoTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetVideoTrack atTime:insertionPoint error:&error];}if (assetAudioTrack != nil) {AVMutableCompositionTrack *compositionAudioTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetAudioTrack atTime:insertionPoint error:&error];}}
//    // Step 2
//    // Translate the composition to compensate the movement caused by rotation (since rotation would cause it to move out of frame)
//    t1 = CGAffineTransformMakeTranslation(assetVideoTrack.naturalSize.height, 0.0);
//    // Rotate transformation
//    t2 = CGAffineTransformRotate(t1, degreesToRadians(90));if (degress == 0) {t1 = CGAffineTransformMakeTranslation(0.0, 0.0);t2 = CGAffineTransformRotate(t1, degreesToRadians(0));}else if (degress == 90){t1 = CGAffineTransformMakeTranslation(assetVideoTrack.naturalSize.height, 0.0);t2 = CGAffineTransformRotate(t1, degreesToRadians(90));}else if (degress == 180){t1 = CGAffineTransformMakeTranslation(assetVideoTrack.naturalSize.width, assetVideoTrack.naturalSize.height);t2 = CGAffineTransformRotate(t1, degreesToRadians(180));}else if (degress == 270){t1 = CGAffineTransformMakeTranslation(0,assetVideoTrack.naturalSize.height*1.78);t2 = CGAffineTransformRotate(t1, degreesToRadians(-90));}// Step 3// Set the appropriate render sizes and rotational transformsif (!mutableVideoComposition) {// Create a new video compositionmutableVideoComposition = [AVMutableVideoComposition videoComposition];if (degress == 0 || degress == 180) {mutableVideoComposition.renderSize = CGSizeMake(assetVideoTrack.naturalSize.width,assetVideoTrack.naturalSize.height);}else{mutableVideoComposition.renderSize = CGSizeMake(assetVideoTrack.naturalSize.height,assetVideoTrack.naturalSize.width);}mutableVideoComposition.frameDuration = CMTimeMake(1, 30);// The rotate transform is set on a layer instructioninstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mutableComposition duration]);layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:(mutableComposition.tracks)[0]];[layerInstruction setTransform:t2 atTime:kCMTimeZero];} else {mutableVideoComposition.renderSize = CGSizeMake(mutableVideoComposition.renderSize.height, mutableVideoComposition.renderSize.width);// Extract the existing layer instruction on the mutableVideoCompositioninstruction = (mutableVideoComposition.instructions)[0];layerInstruction = (instruction.layerInstructions)[0];// Check if a transform already exists on this layer instruction, this is done to add the current transform on top of previous editsCGAffineTransform existingTransform;if (![layerInstruction getTransformRampForTime:[mutableComposition duration] startTransform:&existingTransform endTransform:NULL timeRange:NULL]) {[layerInstruction setTransform:t2 atTime:kCMTimeZero];} else {// Note: the point of origin for rotation is the upper left corner of the composition, t3 is to compensate for originCGAffineTransform t3 = CGAffineTransformMakeTranslation(-1*assetVideoTrack.naturalSize.height/2, 0.0);CGAffineTransform newTransform = CGAffineTransformConcat(existingTransform, CGAffineTransformConcat(t2, t3));[layerInstruction setTransform:newTransform atTime:kCMTimeZero];}}// Step 4// Add the transform instructions to the video compositioninstruction.layerInstructions = @[layerInstruction];mutableVideoComposition.instructions = @[instruction];

到这个时候呢视频的旋转已经完成了。
上面我们不是写了一个视频压缩的方法吗？把这个时候生成的mutableVideoComposition赋值给session.videoComposition = mutableVideoComposition;就好了。这样就是先旋转视频然后直接压缩完成我们的需求。