使用AVFoundation生成视频缩略图

概述

AVFoundation生成视频缩略图主要靠如下两个类. AVURLAsset、AVAssetImageGenerator

使用AVFoundation生成视频缩略图的步骤如下

1、根据视频的NSURL创建AVURLAsset对象

   NSString *path = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"MOV"];
   AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:path] options:nil];

2、根据AVURLAsset对象创建AVAssetImageGenerator对象

    AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
    generator.appliesPreferredTrackTransform = YES;
    generator.requestedTimeToleranceAfter = kCMTimeZero;
    generator.requestedTimeToleranceBefore = kCMTimeZero;

3、生成图像

    //CMTime是专门用于标识电影时间的结构体
    /**
     CMTimeMake(int64_t  value, int_32  timescale):
     第1个参数代表获取第几帧的截图,
     第2个参数代表每秒的帧数.因此实际截取的时间点是value/timescale.
     
     CMTimeMakeWithSeconds(Float64  seconds, int32_t  preferredTimeScale):
     第1个参数代表获取第几秒的截图,
     第2个参数则代表每秒的帧数.
     */
    CMTime time = CMTimeMakeWithSeconds(atTime, 600);
    NSError *error = nil;
    CMTime actualTime;
    
    //获取该视频指定时间点的视频截图
    /**
     该方法的第一个CMTime参数用于指定获取哪个时间点的视频截图
     第2个CMTime参数用于获取实际截图 位于哪个时间点.
     */
    CGImageRef image = [generator copyCGImageAtTime:time actualTime:&actualTime error:&error];
    
    UIImage *img = [[UIImage alloc] initWithCGImage:image];
    UIGraphicsBeginImageContext(CGSizeMake([[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width, [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height));
    [img drawInRect:CGRectMake(0, 0, [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width, [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height)];
    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRelease(image);

4、获取视频时长

//获取本地视频的时长
- (NSUInteger)durationWithVideo:(NSString *)videoPath {
    NSDictionary *opts = @{AVURLAssetPreferPreciseDurationAndTimingKey: @(NO)};
    AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:videoPath] options:opts];     //初始化视频媒体文件
    NSUInteger second = 0;
    second = ceilf((double)urlAsset.duration.value / (double)urlAsset.duration.timescale); // 获取视频总时长,单位秒
    return second;
}

5、获取每一秒的图片

self.videoDuration = [self durationWithVideo:self.videoUrlStr]; 
  //每隔1s截取一张图片
 for (int i = 0; i < self.videoDuration-1; i++) {
        UIImage *image = [self getVideoPreViewImageFromVideoPath:self.videoUrlStr withAtTime:i+0.1];
        [coverImgs addObject:image];       
 }

6、图片数组添加到scrollView

 //图片宽
    float imgWidth = self.maxWidth/10.0;
    for (int i = 0; i< self.coverImgs.count; i++) {
        UIImageView *imageView = [[UIImageView alloc] initWithImage:[self.coverImgs objectAtIndex:i]];
        [imageView setFrame:CGRectMake(i*imgWidth, 0, imgWidth, 50)];
        [self.scrollView addSubview:imageView];
    }
    [self.scrollView setContentSize:CGSizeMake(imgWidth*self.coverImgs.count, 50)];

未完待续...
Demo稍后奉上