AVCaptureStillImageOutput.pngStillImageNSDataRepresentation？

Question

我是第一次使用 AVCaptureStillImageOutput，我在某个时候保存了一张 JPEG 图像。 我想保存 PNG 图像而不是 JPEG 图像。我需要为此做什么？

我在应用程序中有这 3 行代码：

let stillImageOutput = AVCaptureStillImageOutput()
stillImageOutput.outputSettings = [AVVideoCodecKey:AVVideoCodecJPEG]
let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(imageDataSampleBuffer)

有没有一种简单的方法来修改这些行以获得我想要的内容？ 上网查了一下好像答案是NO（除非我运气不够好），不过我还是相信一定有好的解决办法。

Answer 1

AVFoundation Programming Guide 中的示例代码展示了如何将 CMSampleBuffer 转换为 UIImage（在 Converting CMSampleBuffer to a UIImage Object 下）。从那里，您可以使用 UIImagePNGRepresentation(image) 将其编码为 PNG 数据。

这是该代码的 Swift 翻译：

extension UIImage
{
    // Translated from <https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/06_MediaRepresentations.html#//apple_ref/doc/uid/TP40010188-CH2-SW4>
    convenience init?(fromSampleBuffer sampleBuffer: CMSampleBuffer)
    {
        guard let imageBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return nil }

        if CVPixelBufferLockBaseAddress(imageBuffer, kCVPixelBufferLock_ReadOnly) != kCVReturnSuccess { return nil }
        defer { CVPixelBufferUnlockBaseAddress(imageBuffer, kCVPixelBufferLock_ReadOnly) }

        let context = CGBitmapContextCreate(
            CVPixelBufferGetBaseAddress(imageBuffer),
            CVPixelBufferGetWidth(imageBuffer),
            CVPixelBufferGetHeight(imageBuffer),
            8,
            CVPixelBufferGetBytesPerRow(imageBuffer),
            CGColorSpaceCreateDeviceRGB(),
            CGBitmapInfo.ByteOrder32Little.rawValue | CGImageAlphaInfo.PremultipliedFirst.rawValue)

        guard let quartzImage = CGBitmapContextCreateImage(context) else { return nil }
        self.init(CGImage: quartzImage)
    }
}

Answer 2

这是上述代码的 Swift 4 版本。

extension UIImage
{
    convenience init?(fromSampleBuffer sampleBuffer: CMSampleBuffer)
    {
        guard let imageBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return nil }

        if CVPixelBufferLockBaseAddress(imageBuffer, .readOnly) != kCVReturnSuccess { return nil }
        defer { CVPixelBufferUnlockBaseAddress(imageBuffer, .readOnly) }

        let context = CGContext(
        data: CVPixelBufferGetBaseAddress(imageBuffer),
        width: CVPixelBufferGetWidth(imageBuffer),
        height: CVPixelBufferGetHeight(imageBuffer),
        bitsPerComponent: 8,
        bytesPerRow: CVPixelBufferGetBytesPerRow(imageBuffer),
        space: CGColorSpaceCreateDeviceRGB(),
        bitmapInfo: CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)

        guard let quartzImage = context!.makeImage() else { return nil }
        self.init(cgImage: quartzImage)
    }
}