『ios』视频编辑入门【添加水印】

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添加水印也是拿AVFoundation搞得，好像拿GPUImage也可以搞。
这块内容对自己来说就是空白，只能一点一点分析别人的源码。

1.拿到资源

  NSDictionary *opts = [NSDictionary dictionaryWithObject:@(YES) forKey:AVURLAssetPreferPreciseDurationAndTimingKey];
  //视频资源
    videoAsset = [AVURLAsset URLAssetWithURL:videoPath options:opts]; 
   //声音采集
    AVURLAsset * audioAsset = [[AVURLAsset alloc] initWithURL:videoPath options:opts];

2.创建视频合成文件

 AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];

3.视频轨道插入素材

  AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                        preferredTrackID:kCMPersistentTrackID_Invalid];

    [videoTrack insertTimeRange:CMTimeRangeFromTimeToTime(startTime, endTime)
                        ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
                         atTime:kCMTimeZero error:nil];

4.音频轨道

    AVMutableCompositionTrack * audioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    //音频采集通道
    AVAssetTrack * audioAssetTrack = [[audioAsset tracksWithMediaType:AVMediaTypeAudio] firstObject];
    [audioTrack insertTimeRange:CMTimeRangeFromTimeToTime(startTime, endTime) ofTrack:audioAssetTrack atTime:kCMTimeZero error:nil];

5.合成视频

//一个指令，决定一个timeRange内每个轨道的状态，包含多个layerInstruction
    AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    mainInstruction.timeRange = CMTimeRangeFromTimeToTime(kCMTimeZero, videoTrack.timeRange.duration);
//在一个指令的时间范围内，某个轨道的状态
   AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
    AVAssetTrack *videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
   BOOL isVideoAssetPortrait_  = NO;
    CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;
    if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {
        //        videoAssetOrientation_ = UIImageOrientationRight;
        isVideoAssetPortrait_ = YES;
    }
    if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {
        //        videoAssetOrientation_ =  UIImageOrientationLeft;
        isVideoAssetPortrait_ = YES;
    }
//调整视频方向
 [videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
    [videolayerInstruction setOpacity:0.0 atTime:endTime];
 mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];

6.AVMutableVideoComposition：管理所有视频轨道，可以决定最终视频的尺寸，裁剪需要在这里进行

  AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];
    
    CGSize naturalSize;
    if(isVideoAssetPortrait_){
        naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
    } else {
        naturalSize = videoAssetTrack.naturalSize;
    }
    
    float renderWidth, renderHeight;
    renderWidth = naturalSize.width;
    renderHeight = naturalSize.height;
    mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
    mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
    mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
    mainCompositionInst.frameDuration = CMTimeMake(1, 25);

7.水印 AVVideoCompositionCoreAnimationTool

   //水印
    CALayer *imgLayer = [CALayer layer];
    imgLayer.contents = (id)img.CGImage;
//    imgLayer.bounds = CGRectMake(0, 0, size.width, size.height);
    imgLayer.bounds = CGRectMake(0, 0, 210, 50);
    imgLayer.position = CGPointMake(size.width/2.0, size.height/2.0);
    
    //第二个水印
    CALayer *coverImgLayer = [CALayer layer];
    coverImgLayer.contents = (id)coverImg.CGImage;
//    [coverImgLayer setContentsGravity:@"resizeAspect"];
    coverImgLayer.bounds =  CGRectMake(50, 200,210, 50);
    coverImgLayer.position = CGPointMake(size.width/4.0, size.height/4.0);
    
    // 2 - The usual overlay
    CALayer *overlayLayer = [CALayer layer];
    [overlayLayer addSublayer:subtitle1Text];
    [overlayLayer addSublayer:imgLayer];
    overlayLayer.frame = CGRectMake(0, 0, size.width, size.height);
    [overlayLayer setMasksToBounds:YES];
    
    CALayer *parentLayer = [CALayer layer];
    CALayer *videoLayer = [CALayer layer];
    parentLayer.frame = CGRectMake(0, 0, size.width, size.height);
    videoLayer.frame = CGRectMake(0, 0, size.width, size.height);
    [parentLayer addSublayer:videoLayer];
    [parentLayer addSublayer:overlayLayer];
    [parentLayer addSublayer:coverImgLayer];
    
    //设置封面
    CABasicAnimation *anima = [CABasicAnimation animationWithKeyPath:@"opacity"];
    anima.fromValue = [NSNumber numberWithFloat:1.0f];
    anima.toValue = [NSNumber numberWithFloat:0.0f];
    anima.repeatCount = 0;
    anima.duration = 5.0f;  //5s之后消失
    [anima setRemovedOnCompletion:NO];
    [anima setFillMode:kCAFillModeForwards];
    anima.beginTime = AVCoreAnimationBeginTimeAtZero;
    [coverImgLayer addAnimation:anima forKey:@"opacityAniamtion"];
    //主要是下面这个方法
    composition.animationTool = [AVVideoCompositionCoreAnimationTool
                                 videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];

8.获取文件路径导出视频

  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    
    NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.mp4",fileName]];
    unlink([myPathDocs UTF8String]);
    NSURL* videoUrl = [NSURL fileURLWithPath:myPathDocs];
    exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                presetName:AVAssetExportPresetHighestQuality];
    exporter.outputURL=videoUrl;
    exporter.outputFileType = AVFileTypeQuickTimeMovie;
    exporter.shouldOptimizeForNetworkUse = YES;
    exporter.videoComposition = mainCompositionInst;
    [exporter exportAsynchronouslyWithCompletionHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            //这里是输出视频之后的操作，做你想做的
            [self exportDidFinish:exporter];
        });
    }];

- (void)exportDidFinish:(AVAssetExportSession*)session {
    if (session.status == AVAssetExportSessionStatusCompleted) {
        NSURL *outputURL = session.outputURL;
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            __block PHObjectPlaceholder *placeholder;
            if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(outputURL.path)) {
                NSError *error;
                [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
                    PHAssetChangeRequest* createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromVideoAtFileURL:outputURL];
                    placeholder = [createAssetRequest placeholderForCreatedAsset];
                } error:&error];
                if (error) {
                    [SVProgressHUD showErrorWithStatus:[NSString stringWithFormat:@"%@",error]];
                }
                else{
                    [SVProgressHUD showSuccessWithStatus:@"视频已经保存到相册"];
                }
            }else {
                [SVProgressHUD showErrorWithStatus:NSLocalizedString(@"视频保存相册失败，请设置软件读取相册权限", nil)];
            }
        });
    }
}