How to initialise CVPixelBufferRef in Swift

Question

We used to initialize CVPixelBufferRef like below.

  CVPixelBufferRef pxbuffer = NULL;

But in Swift we can not use NULL, so we tried following but of course XCODE want us to have it initalized to use it

let pxbuffer: CVPixelBufferRef

but how ?

In Obj_C we were creating buffer like this, but as I was trying to explain above when converting to Swift I have been stopped at first line.

 CVPixelBufferRef pxbuffer = NULL;

CVPixelBufferCreate(kCFAllocatorDefault, picGenislik,
                    frameHeight, kCVPixelFormatType_32ARGB, (__bridge         CFDictionaryRef) options,
                    &pxbuffer);

Any reference that takes `NULL` / `nil` is optional variable, please check my answer there I have created an optional `pixelBuffer` — Inder Kumar Rathore, Oct 10 '15 at 11:56

Inder Kumar Rathore · Answer 1 · 2015-10-10T11:54:39.807

11

Use CVPixelBufferCreate(_:_:_:_:_:_:) to create the object

Adding some demo code, hope this helps you. Also do read Using Legacy C APIs with Swift

var keyCallBack: CFDictionaryKeyCallBacks
var valueCallBacks: CFDictionaryValueCallBacks

var empty: CFDictionaryRef = CFDictionaryCreate(kCFAllocatorDefault, nil, nil, 0, &keyCallBack, &valueCallBacks)

var attributes = CFDictionaryCreateMutable(kCFAllocatorDefault,
    1,
    &keyCallBack,
    &valueCallBacks);


var iOSurfacePropertiesKey = kCVPixelBufferIOSurfacePropertiesKey

withUnsafePointer(&iOSurfacePropertiesKey) { unsafePointer in
    CFDictionarySetValue(attributes, unsafePointer, empty)
}

var width = 10
var height = 12
var pixelBuffer: CVPixelBufferRef? = nil
var status: CVReturn = CVPixelBufferCreate(kCFAllocatorDefault, width, height, kCVPixelFormatType_32BGRA, attributes, &pixelBuffer)

edited Oct 10 '15 at 11:54

answered Oct 10 '15 at 11:26

Inder Kumar Rathore

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I tried CVPixelBufferCreate(kCFAllocatorDefault, width, height, kCVPixelFormatType_32ARGB, options, pxbuffer) after let pxbuffer: CVPixelBufferRef bu no luck there. It did not like pxbuffer. – Hope Oct 10 '15 at 11:31
Your latest addition is made me progress a bit more thanks. But, I wonder why it takes that much code just to open a place in memory for pixel calculations. I do not like reading much thats why maybe. – Hope Oct 10 '15 at 13:21

Samer Murad · Answer 2 · 2017-04-25T09:23:07.570

Here is another way to do it (Swift 3):

var pixelBuffer: UnsafeMutablePointer<CVPixelBuffer?>!
if pixelBuffer == nil {
pixelBuffer = UnsafeMutablePointer<CVPixelBuffer?>.allocate(capacity: MemoryLayout<CVPixelBuffer?>.size)
}
CVPixelBufferCreate(kCFAllocatorDefault, width, height, kCVPixelFormatType_32BGRA, attributes, pixelBuffer)

and then you can access the buffer object like this:

pixelBuffer.pointee

EDIT:

    pixelBuffer = UnsafeMutablePointer<CVPixelBuffer?>.allocate(capacity: MemoryLayout<CVPixelBuffer?>.size)

Creates a memory leak if you don't manually deallocate the pointer when you're done with it, to avoid this change your code to the following:

var pixelBuffer : CVPixelBuffer? = nil
CVPixelBufferCreate(kCFAllocatorDefault, cgimg.width, cgimg.height, kCVPixelFormatType_32BGRA, nil, &pixelBuffer)

You may want to deallocate the pixelBuffer with pixelBuffer.deallocate(capacity: MemoryLayout.size) — Rocket Garden, Apr 25 '17 at 08:56
@RocketGarden You are right, thank you for pointing that, I provided a better solution — Samer Murad, Apr 25 '17 at 09:24

score 0 · Answer 3 · answered Mar 02 '17 at 20:05

func getCVPixelBuffer(_ image: CGImage) -> CVPixelBuffer? {
    let imageWidth = Int(image.width)
    let imageHeight = Int(image.height)

    let attributes : [NSObject:AnyObject] = [
        kCVPixelBufferCGImageCompatibilityKey : true as AnyObject,
        kCVPixelBufferCGBitmapContextCompatibilityKey : true as AnyObject
    ]

    var pxbuffer: CVPixelBuffer? = nil
    CVPixelBufferCreate(kCFAllocatorDefault,
                        imageWidth,
                        imageHeight,
                        kCVPixelFormatType_32ARGB,
                        attributes as CFDictionary?,
                        &pxbuffer)

    if let _pxbuffer = pxbuffer {
        let flags = CVPixelBufferLockFlags(rawValue: 0)
        CVPixelBufferLockBaseAddress(_pxbuffer, flags)
        let pxdata = CVPixelBufferGetBaseAddress(_pxbuffer)

        let rgbColorSpace = CGColorSpaceCreateDeviceRGB();
        let context = CGContext(data: pxdata,
                                width: imageWidth,
                                height: imageHeight,
                                bitsPerComponent: 8,
                                bytesPerRow: CVPixelBufferGetBytesPerRow(_pxbuffer),
                                space: rgbColorSpace,
                                bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue)

        if let _context = context {
            _context.draw(image, in: CGRect.init(x: 0, y: 0, width: imageWidth, height: imageHeight))
        }
        else {
            CVPixelBufferUnlockBaseAddress(_pxbuffer, flags);
            return nil
        }

        CVPixelBufferUnlockBaseAddress(_pxbuffer, flags);
        return _pxbuffer;
    }

    return nil
}

How to initialise CVPixelBufferRef in Swift

3 Answers3

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