Apply visual effect to images pixel by pixel in Swift

Question

I have an university's assignment to create visual effect and apply them to video frames captured through the devices camera. I currently can get the image and display but can't change the pixel color values.

I transform the sample buffer to the imageRef variable and if I transform it to UIImage everything is alright.

But now I want to take that imageRef an change its color's values pixel by pixel, in this example change to negative colors (I have to do more complicated stuff so I can't use CIFilters) but when I execute the commented part it crashed due to bad access.

import UIKit
import AVFoundation

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {

  let captureSession = AVCaptureSession()
  var previewLayer : AVCaptureVideoPreviewLayer?

  var captureDevice : AVCaptureDevice?

  @IBOutlet weak var cameraView: UIImageView!

  override func viewDidLoad() {
    super.viewDidLoad()

    captureSession.sessionPreset = AVCaptureSessionPresetMedium

    let devices = AVCaptureDevice.devices()

    for device in devices {
      if device.hasMediaType(AVMediaTypeVideo) && device.position == AVCaptureDevicePosition.Back {
        if let device = device as? AVCaptureDevice {
          captureDevice = device
          beginSession()
          break
        }
      }
    }
  }

  func focusTo(value : Float) {
    if let device = captureDevice {
      if(device.lockForConfiguration(nil)) {
        device.setFocusModeLockedWithLensPosition(value) {
          (time) in
        }
        device.unlockForConfiguration()
      }
    }
  }

  override func touchesBegan(touches: NSSet!, withEvent event: UIEvent!) {
    var touchPercent = Float(touches.anyObject().locationInView(view).x / 320)
    focusTo(touchPercent)
  }

  override func touchesMoved(touches: NSSet!, withEvent event: UIEvent!) {
    var touchPercent = Float(touches.anyObject().locationInView(view).x / 320)
    focusTo(touchPercent)
  }

  func beginSession() {
    configureDevice()

    var error : NSError?
    captureSession.addInput(AVCaptureDeviceInput(device: captureDevice, error: &error))

    if error != nil {
      println("error: \(error?.localizedDescription)")
    }

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

    previewLayer?.frame = view.layer.frame
    //view.layer.addSublayer(previewLayer)

    let output = AVCaptureVideoDataOutput()
    let cameraQueue = dispatch_queue_create("cameraQueue", DISPATCH_QUEUE_SERIAL)
    output.setSampleBufferDelegate(self, queue: cameraQueue)
    output.videoSettings = [kCVPixelBufferPixelFormatTypeKey: kCVPixelFormatType_32BGRA]

    captureSession.addOutput(output)
    captureSession.startRunning()
  }

  func configureDevice() {
    if let device = captureDevice {
      device.lockForConfiguration(nil)
      device.focusMode = .Locked
      device.unlockForConfiguration()
    }
  }

  // MARK : - AVCaptureVideoDataOutputSampleBufferDelegate

  func captureOutput(captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {
    let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
    CVPixelBufferLockBaseAddress(imageBuffer, 0)

    let baseAddress = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0)
    let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer)
    let width = CVPixelBufferGetWidth(imageBuffer)
    let height = CVPixelBufferGetHeight(imageBuffer)
    let colorSpace = CGColorSpaceCreateDeviceRGB()

    var bitmapInfo = CGBitmapInfo.fromRaw(CGImageAlphaInfo.PremultipliedFirst.toRaw())! | CGBitmapInfo.ByteOrder32Little

    let context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo)
    let imageRef = CGBitmapContextCreateImage(context)

    CVPixelBufferUnlockBaseAddress(imageBuffer, 0)

    let data = CGDataProviderCopyData(CGImageGetDataProvider(imageRef)) as NSData
    let pixels = data.bytes

    var newPixels = UnsafeMutablePointer()

    //for index in stride(from: 0, to: data.length, by: 4) {

      /*newPixels[index] = 255 - pixels[index]
      newPixels[index + 1] = 255 - pixels[index + 1]
      newPixels[index + 2] = 255 - pixels[index + 2]
      newPixels[index + 3] = 255 - pixels[index + 3]*/
    //}

    bitmapInfo = CGImageGetBitmapInfo(imageRef)
    let provider = CGDataProviderCreateWithData(nil, newPixels, UInt(data.length), nil)

    let newImageRef = CGImageCreate(width, height, CGImageGetBitsPerComponent(imageRef), CGImageGetBitsPerPixel(imageRef), bytesPerRow, colorSpace, bitmapInfo, provider, nil, false, kCGRenderingIntentDefault)

    let image = UIImage(CGImage: newImageRef, scale: 1, orientation: .Right)
    dispatch_async(dispatch_get_main_queue()) {
      self.cameraView.image = image
    }
  }
}

Apply visual effect to images pixel by pixel in Swift

Answers (1)

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