将CMSampleBuffer转换为UIImage

Question

这里有一个函数（来自Apple文档），可以将CMSampleBuffer转换成UIImage：

func imageFromSampleBuffer(sampleBuffer: CMSampleBuffer) -> UIImage {
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    var imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0)

    // Get the number of bytes per row for the pixel buffer
    var baseAddress = CVPixelBufferGetBaseAddress(imageBuffer)

    // Get the number of bytes per row for the pixel buffer
    var bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer)
    // Get the pixel buffer width and height
    var width = CVPixelBufferGetWidth(imageBuffer)
    var height = CVPixelBufferGetHeight(imageBuffer)

    // Create a device-dependent RGB color space
    var colorSpace = CGColorSpaceCreateDeviceRGB()

    // Create a bitmap graphics context with the sample buffer data
    let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.NoneSkipLast.rawValue)
    var context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo)
    // Create a Quartz image from the pixel data in the bitmap graphics context
    var quartzImage = CGBitmapContextCreateImage(context);
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Create an image object from the Quartz image
    var image = UIImage(CGImage: quartzImage)!

    return image
}

当我试图使用UIImageView来可视化UIImage时，却什么也看不到。有任何想法吗？

- Joe

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你在 Xcode 输出中遇到了错误吗？ - Aaron Bratcher

Answer 1

我在当前项目中刚刚完成了同样的功能，以下是我是如何使其工作的（经过大量谷歌搜索和一些试错）：

let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.NoneSkipFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue)

同时，确保在主线程中呈现UIImageView（您可能在相机会话线程中获取CMSampleBuffer），因为UIKit只能在主线程中执行。否则，您将不得不等待非常非常长的时间才能显示图像。

- yuji

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如何在最佳实践中从“bitmapInfo”获取UIImage？ - Alston

Answer 2

@Zigglzworth 需要设置kCVPixelFormatType_32BGRA来捕获视频数据输出。

        let videoOutput = AVCaptureVideoDataOutput()
        videoOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_32BGRA]

- Chuong Tran

Answer 3

这是一个针对Swift 3.0的解决方案，扩展了，创建了一个变量，为您提供可选的。

import AVFoundation

extension CMSampleBuffer {
    var uiImage: UIImage? {
        guard let imageBuffer = CMSampleBufferGetImageBuffer(self) else { return nil }

        CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))
        let baseAddress = CVPixelBufferGetBaseAddress(imageBuffer)
        let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer)
        let width = CVPixelBufferGetWidth(imageBuffer)
        let height = CVPixelBufferGetHeight(imageBuffer)
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.noneSkipFirst.rawValue | CGBitmapInfo.byteOrder32Little.rawValue)
        guard let context = CGContext(data: baseAddress,
                                      width: width,
                                      height: height,
                                      bitsPerComponent: 8,
                                      bytesPerRow: bytesPerRow,
                                      space: colorSpace,
                                      bitmapInfo: bitmapInfo.rawValue) else { return nil }
        guard let cgImage = context.makeImage() else { return nil }

        CVPixelBufferUnlockBaseAddress(imageBuffer,CVPixelBufferLockFlags(rawValue: 0));

        return UIImage(cgImage: cgImage)
    }
}

- CodeBender

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我收到以下错误信息：<Error>: CGBitmapContextCreate: invalid data bytes/row: should be at least 5120 for 8 integer bits/component, 3 components, kCGImageAlphaNoneSkipFirst - Zigglzworth

@Zigglzworth 您可能有一张灰度图像。您可以相应地调整值。 - CodeBender

嗯，这不是应该……不确定为什么这对我没用。 - Zigglzworth

你能否把图片发布到某个地方？ - CodeBender

@CodeBender 非常感谢 :) - Nikhil Manapure

如何将其转换回 CMSampleBuffer？ - famfamfam