首页 文章

使用Swift从视频中抓取帧

提问于
浏览 次
6

我想在特定时间从视频中抓取帧 . 我正在调用我的抓帧功能，其时间指定为秒为Float64 . 问题是它没有 grab 当前帧 . 它似乎忽略了小数 . 如果我用例如1.22和1.70调用该函数，它将返回相同的帧 . 对于Swift来说，我是新手，所以我猜我没有把CMTime对象弄好 . 所以有人能看出这有什么问题吗？

func generateThumnail(url : NSURL, fromTime:Float64) -> UIImage {
    var asset :AVAsset = AVAsset.assetWithURL(url) as! AVAsset
    var assetImgGenerate : AVAssetImageGenerator = AVAssetImageGenerator(asset: asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    var error       : NSError? = nil
    var time        : CMTime = CMTimeMakeWithSeconds(fromTime, 600)        
    var img         : CGImageRef = assetImgGenerate.copyCGImageAtTime(time, actualTime: nil, error: &error)
    var frameImg    : UIImage = UIImage(CGImage: img)!
    return frameImg
}

var grabTime = 1.22
img = generateThumnail(urlVideo, fromTime: Float64(grabTime))
swift video avfoundation

3 回答

  • 12

    感谢@ eric-d发现了这篇文章：iOS Take Multiple Screen Shots

    我设法找出添加：

    assetImgGenerate.requestedTimeToleranceAfter = kCMTimeZero;
    assetImgGenerate.requestedTimeToleranceBefore = kCMTimeZero;

    ...我的功能将会做到这一点 .

    我更新的函数如下所示：

    func generateThumnail(url : NSURL, fromTime:Float64) -> UIImage {
    var asset :AVAsset = AVAsset.assetWithURL(url) as! AVAsset
    var assetImgGenerate : AVAssetImageGenerator = AVAssetImageGenerator(asset: asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    assetImgGenerate.requestedTimeToleranceAfter = kCMTimeZero;
    assetImgGenerate.requestedTimeToleranceBefore = kCMTimeZero;
    var error       : NSError? = nil
    var time        : CMTime = CMTimeMakeWithSeconds(fromTime, 600)        
    var img         : CGImageRef = assetImgGenerate.copyCGImageAtTime(time, actualTime: nil, error: &error)
    var frameImg    : UIImage = UIImage(CGImage: img)!
    return frameImg
}

var grabTime = 1.22
img = generateThumnail(urlVideo, fromTime: Float64(grabTime))
    回复于
  • 1

    我将arpo的答案纳入了我的项目，更新了Swift 3：

    fileprivate func generateThumnail(url : URL, fromTime:Float64) -> UIImage? {
    let asset :AVAsset = AVAsset(url: url)
    let assetImgGenerate : AVAssetImageGenerator = AVAssetImageGenerator(asset: asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    assetImgGenerate.requestedTimeToleranceAfter = kCMTimeZero;
    assetImgGenerate.requestedTimeToleranceBefore = kCMTimeZero;
    let time        : CMTime = CMTimeMakeWithSeconds(fromTime, 600)
    if let img = try? assetImgGenerate.copyCGImage(at:time, actualTime: nil) {
        return UIImage(cgImage: img!)
    } else {
        return nil
    }
}
    回复于
  • 0

    对于swift 4.2

    fileprivate func generateThumnail(url : URL, fromTime:Float64) -> UIImage? {
    let asset :AVAsset = AVAsset(url: url)
    let assetImgGenerate : AVAssetImageGenerator = AVAssetImageGenerator(asset: asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    assetImgGenerate.requestedTimeToleranceAfter = CMTime.zero;
    assetImgGenerate.requestedTimeToleranceBefore = CMTime.zero;
    let time : CMTime = CMTimeMakeWithSeconds(fromTime, preferredTimescale: 600)
    if let img = try? assetImgGenerate.copyCGImage(at:time, actualTime: nil) {
        return UIImage(cgImage: img)
    } else {
        return nil
    }
}
    回复于

相关问题