How to convert a UIImage to a CVPixelBuffer 32BGRA for mediapipe? - ios

Question

I am using mediapipe to develop a iOS application, now I need input an image data to the mediapipe, but mediapipe only accepted 32BGRA CVPixelBuffer.
how can I convert UIImage to 32BGRA CVPixelBuffer?
I am using this code:
let frameSize = CGSize(width: self.cgImage!.width, height: self.cgImage!.height)
var pixelBuffer:CVPixelBuffer? = nil
let status = CVPixelBufferCreate(kCFAllocatorDefault, Int(frameSize.width), Int(frameSize.height), kCVPixelFormatType_32BGRA , nil, &pixelBuffer)
if status != kCVReturnSuccess {
return nil
}
CVPixelBufferLockBaseAddress(pixelBuffer!, CVPixelBufferLockFlags.init(rawValue: 0))
let data = CVPixelBufferGetBaseAddress(pixelBuffer!)
let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)
let context = CGContext(data: data, width: Int(frameSize.width), height: Int(frameSize.height), bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(pixelBuffer!), space: rgbColorSpace, bitmapInfo: bitmapInfo.rawValue)
context?.draw(self.cgImage!, in: CGRect(x: 0, y: 0, width: self.cgImage!.width, height: self.cgImage!.height))
CVPixelBufferUnlockBaseAddress(pixelBuffer!, CVPixelBufferLockFlags(rawValue: 0))
return pixelBuffer
but I will throw an error on mediapipe mediapipe/0 (11): signal SIGABRT
If I use AVCaptureVideoDataOutput it is all well.
btw: I am using swift.

Answer 1

Maybe you can try this. Also, I have a question for you. Do you know how to use a static image?
Are used for face recognition in mediapipe? If you know, please tell me. Thank you.
func pixelBufferFromCGImage(image:CGImage) -> CVPixelBuffer? {
let options = [
kCVPixelBufferCGImageCompatibilityKey as String: NSNumber(value: true),
kCVPixelBufferCGBitmapContextCompatibilityKey as String: NSNumber(value: true),
kCVPixelBufferIOSurfacePropertiesKey as String: [:]
] as CFDictionary
let size:CGSize = .init(width: image.width, height: image.height)
var pxbuffer: CVPixelBuffer? = nil
let status = CVPixelBufferCreate(
kCFAllocatorDefault,
Int(size.width),
Int(size.height),
kCVPixelFormatType_32BGRA,
options,
&pxbuffer)
guard let pxbuffer = pxbuffer else { return nil }
CVPixelBufferLockBaseAddress(pxbuffer, [])
guard let pxdata = CVPixelBufferGetBaseAddress(pxbuffer) else {return nil}
let bitmapInfo = CGBitmapInfo(rawValue: CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)
guard let context = CGContext(data: pxdata, width: Int(size.width), height: Int(size.height), bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(pxbuffer), space: CGColorSpaceCreateDeviceRGB(), bitmapInfo:bitmapInfo.rawValue) else {
return nil
}
context.concatenate(CGAffineTransformIdentity)
context.draw(image, in: .init(x: 0, y: 0, width: size.width, height: size.height))
///error: CGContextRelease' is unavailable: Core Foundation objects are automatically memory managed
///maybe CGContextRelease should not use it
CGContextRelease(context)
CVPixelBufferUnlockBaseAddress(pxbuffer, [])
return pxbuffer
}