Creating thumbnail from local video in swift

问题

How to create thumbnail in swift from a local video file ?

For example if the video file path is located here :

file:///Users/Dev/Library/Developer/CoreSimulator/Devices/F33222DF-D8F0-448B-A127-C5B03C64D0DC/data/Containers/Data/Application/4BC62DBF-0108-453C-9324-5BC0E356FE24/tmp/trim.059D11E6-F0EF-43DB-9E97-CA4F1F95D6B6.MOV

Thank you.

回答1:

Translated with some edits from:

First frame of a video using AVFoundation

    var err: NSError? = nil
    let asset = AVURLAsset(URL: NSURL(fileURLWithPath: "/that/long/path"), options: nil)
    let imgGenerator = AVAssetImageGenerator(asset: asset)
    let cgImage = imgGenerator.copyCGImageAtTime(CMTimeMake(0, 1), actualTime: nil, error: &err)
    // !! check the error before proceeding
    let uiImage = UIImage(CGImage: cgImage)
    let imageView = UIImageView(image: uiImage)
    // lay out this image view, or if it already exists, set its image property to uiImage

回答2:

BaseZen's answer translated Swift 3 / Swift 4

You need to set the location of the video you want to make a thumbnail of as the url asset path, like:

Don't forget to import AVFoundation

func generateThumbnail(path: URL) -> UIImage? {
    do {
        let asset = AVURLAsset(url: path, options: nil)
        let imgGenerator = AVAssetImageGenerator(asset: asset)
        imgGenerator.appliesPreferredTrackTransform = true
        let cgImage = try imgGenerator.copyCGImage(at: CMTimeMake(value: 0, timescale: 1), actualTime: nil)
        let thumbnail = UIImage(cgImage: cgImage)
        return thumbnail
    } catch let error {
        print("*** Error generating thumbnail: \(error.localizedDescription)")
        return nil
    }
}

For everyone having issues with this I have created the following drop in example hosted on Github

回答3:

This is a cleaned up version of David's answer and tested against iOS 11 / Swift 4.x.

Please note the different calls for handling the initial time based on which version of Swift you are using.

func generateThumbnail(url: URL) -> UIImage? {
    do {
        let asset = AVURLAsset(url: url)
        let imageGenerator = AVAssetImageGenerator(asset: asset)
        imageGenerator.appliesPreferredTrackTransform = true
        // Select the right one based on which version you are using
        // Swift 4.2
        let cgImage = try imageGenerator.copyCGImage(at: .zero,
                                                     actualTime: nil)
        // Swift 4.0
        let cgImage = try imageGenerator.copyCGImage(at: kCMTimeZero,
                                                     actualTime: nil)


        return UIImage(cgImage: cgImage)
    } catch {
        print(error.localizedDescription)

        return nil
    }
}

1. Creates an AVURLAsset from the provided URL
2. Creates an AVAssetImageGenerator using the newly created AVURLAsset, is responsible for making the thumbnail
3. appliesPreferredTrackTransform informs the generator to apply the matrix to the thumbnail generation. The default value is false.
4. Attempts to create a CGImage at the first frame of the video track
5. Creates a UIImage using the newly created CGImage & returns it
6. If the image generation step fails, an error is caught and presented to the console along with a nil UIImage

回答4:

BaseZen's answer translated to Swift 2:

import UIKit
import AVFoundation

do {
    let asset = AVURLAsset(URL: NSURL(fileURLWithPath: "/that/long/path"), options: nil)
    let imgGenerator = AVAssetImageGenerator(asset: asset)
    imgGenerator.appliesPreferredTrackTransform = true
    let cgImage = try imgGenerator.copyCGImageAtTime(CMTimeMake(0, 1), actualTime: nil)
    let uiImage = UIImage(CGImage: cgImage)
    let imageView = UIImageView(image: uiImage)
    // lay out this image view, or if it already exists, set its image property to uiImage
} catch let error as NSError {
    print("Error generating thumbnail: \(error)")
}

回答5:

It's better to write less and simple code for understanding. This is what I convert the solutions in Swift (3.1 ... 4.2)

import AVFoundation

func videoPreviewUIImage(moviePath: URL) -> UIImage? {
    let asset = AVURLAsset(url: moviePath)
    let generator = AVAssetImageGenerator(asset: asset)
    generator.appliesPreferredTrackTransform = true
    let timestamp = CMTime(seconds: 2, preferredTimescale: 60)
    if let imageRef = try? generator.copyCGImage(at: timestamp, actualTime: nil) {
        return UIImage(cgImage: imageRef)
    } else {
        return nil
    }
}

Hope it will help someone.

回答6:

func saveImageDocumentDirectoryWithDate(tempImage:UIImage, block : @escaping (_ url: URL?) -> Void ){

    let documentsDirectoryURL = try! FileManager().url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)

    let random : String =  randomString(length: 5)

    let fileURL = documentsDirectoryURL.appendingPathComponent(String(format:"CPImage%@.png",random))
    do { try tempImage.pngData()?.write(to: fileURL) }
    catch { block(nil) }
    block(fileURL)}

来源：https://stackoverflow.com/questions/31779150/creating-thumbnail-from-local-video-in-swift