title: vImageBoxConvolve_ARGB8888 backgroundColor parameter
body: <p>I use the vImageBoxConvolve_ARGB8888 function in order to blur a UIImage. The code is shown below:</p>
  
  <pre><code>public func blur(_ size: Int) -&gt; UIImage! {       
      let boxSize = size - (size % 2) + 1
      let image = self.cgImage
      let inProvider = image?.dataProvider
  
      let height = vImagePixelCount((image?.height)!)
      let width = vImagePixelCount((image?.width)!)
      let rowBytes = image?.bytesPerRow
  
      var inBitmapData = inProvider?.data
      let inData = UnsafeMutableRawPointer(mutating: CFDataGetBytePtr(inBitmapData))
      var inBuffer = vImage_Buffer(data: inData, height: height, width: width, rowBytes: rowBytes!)
  
      let outData = malloc((image?.bytesPerRow)! * (image?.height)!)
      var outBuffer = vImage_Buffer(data: outData, height: height, width: width, rowBytes: rowBytes!)
  
      var error = vImageBoxConvolve_ARGB8888(&amp;inBuffer, &amp;outBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, vImage_Flags(kvImageEdgeExtend))
      error = vImageBoxConvolve_ARGB8888(&amp;outBuffer, &amp;inBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, vImage_Flags(kvImageEdgeExtend))
      error = vImageBoxConvolve_ARGB8888(&amp;inBuffer, &amp;outBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, vImage_Flags(kvImageEdgeExtend))
      inBitmapData = nil
      let colorSpace = CGColorSpaceCreateDeviceRGB()
      let context = CGContext(data: outBuffer.data, width: Int(outBuffer.width), height: Int(outBuffer.height), bitsPerComponent: 8, bytesPerRow: outBuffer.rowBytes, space: colorSpace, bitmapInfo: (image?.bitmapInfo.rawValue)!, releaseCallback: {(ptr1, ptr2) in
      }, releaseInfo: outData)!
      var imageRef = context.makeImage()
      let bluredImage = UIImage(cgImage: imageRef!)
      imageRef = nil
      free(outData)
      context.flush()
      context.synchronize()
      return bluredImage
  }
  </code></pre>
  
  <p>The vImageBoxConvolve_ARGB8888 function accepts a background color parameter (the 8th parameter) which is of type UnsafePointer. Here the parameter in nil, but I want to set it in red color. I have no idea how to do that. If someone could give any tips I would appreciate. Thanks in advance.</p>