UIImage+CVPixelBuffer.swift

import UIKit

extension UIImage {
  /**
   Resizes the image to width x height and converts it to an RGB CVPixelBuffer.
  */
  public func pixelBuffer(width: Int, height: Int) -> CVPixelBuffer? {
    var maybePixelBuffer: CVPixelBuffer?
    let attrs = [kCVPixelBufferCGImageCompatibilityKey: kCFBooleanTrue,
                 kCVPixelBufferCGBitmapContextCompatibilityKey: kCFBooleanTrue]
    let status = CVPixelBufferCreate(kCFAllocatorDefault,
                                     width,
                                     height,
                                     kCVPixelFormatType_32ARGB,
                                     attrs as CFDictionary,
                                     &maybePixelBuffer)

    guard status == kCVReturnSuccess, let pixelBuffer = maybePixelBuffer else {
      return nil
    }

    CVPixelBufferLockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))
    let pixelData = CVPixelBufferGetBaseAddress(pixelBuffer)

    guard let context = CGContext(data: pixelData,
                                  width: width,
                                  height: height,
                                  bitsPerComponent: 8,
                                  bytesPerRow: CVPixelBufferGetBytesPerRow(pixelBuffer),
                                  space: CGColorSpaceCreateDeviceRGB(),
                                  bitmapInfo: CGImageAlphaInfo.noneSkipFirst.rawValue)
    else {
      return nil
    }

    context.translateBy(x: 0, y: CGFloat(height))
    context.scaleBy(x: 1, y: -1)

    UIGraphicsPushContext(context)
    self.draw(in: CGRect(x: 0, y: 0, width: width, height: height))
    UIGraphicsPopContext()
    CVPixelBufferUnlockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))

    return pixelBuffer
  }
}