IOS swift 原始横向图片旋转为竖向旋转

2020-05-08 04:16:35 计算机视觉

ios Swift

iOS相机默认输出是个横向图，需要将其转为竖向，网上试了一些方法效率都不是很高，因为在做实时的图像算法，所以对FPS要求很高，用accelerate框架自己写了一个转竖向图的方法

基于CVPixelBuffer写了一个extension

extension CVPixelBuffer {
    public func ro() -> CVPixelBuffer? {
        let size = CGRect(origin: CGPoint(x: 0, y: 0), size: self.size)

        let inputImageRowBytes = CVPixelBufferGetBytesPerRow(self)
        let imageChannels = 4

        CVPixelBufferLockBaseAddress(self, CVPixelBufferLockFlags(rawValue: 0))
        defer { CVPixelBufferUnlockBaseAddress(self, CVPixelBufferLockFlags(rawValue: 0)) }

        // Finds the address of the upper leftmost pixel of the source area.
        guard
          let inputBaseAddress = CVPixelBufferGetBaseAddress(self)?.advanced(
            by: Int(size.minY) * inputImageRowBytes + Int(size.minX) * imageChannels)
        else {
          return nil
        }

        // Crops given area as vImage Buffer.
        var croppedImage = vImage_Buffer(
          data: inputBaseAddress, height: UInt(self.size.height), width: UInt(self.size.width),
          rowBytes: inputImageRowBytes)

        // ======

        let paddedRotatedRowBytes = Int(size.height) * imageChannels
        guard let paddedRotatedAddress = malloc(Int(size.width) * paddedRotatedRowBytes) else {
          return nil
        }

        // Allocates a vacant vImage buffer for resized image.
        var paddedRotatedImage = vImage_Buffer(
          data: paddedRotatedAddress,
          height: UInt(size.width), width: UInt(size.height),
          rowBytes: paddedRotatedRowBytes
        )

        var cg_transform = vImage_CGAffineTransform(a: 0.0, b: -1, c: 1, d: 0.0, tx: Double(0), ty: Double(size.width))
        guard vImageAffineWarpCG_ARGB8888(&croppedImage, &paddedRotatedImage, nil, &cg_transform, clear_color, vImage_Flags(0)) == kvImageNoError else {
            free(paddedRotatedAddress)
            return nil
        }

        let releaseCallBack: CVPixelBufferReleaseBytesCallback = { mutablePointer, pointer in
          if let pointer = pointer {
            free(UnsafeMutableRawPointer(mutating: pointer))
          }
        }

        var result: CVPixelBuffer?

        // Converts the thumbnail vImage buffer to CVPixelBuffer
        let conversionStatus = CVPixelBufferCreateWithBytes(
          nil,
          Int(size.height), Int(size.width),
          CVPixelBufferGetPixelFormatType(self),
          paddedRotatedAddress,
          paddedRotatedRowBytes,
          releaseCallBack,
          nil,
          nil,
          &result
        )

        guard conversionStatus == kCVReturnSuccess else {
          free(paddedRotatedAddress)
          return nil
        }

        return result
      }
}

调用方法也很简单，只需要直接.ro即可

guard let rPixelBuffer = oPixelBuffer.ro() else {
        return nil
}

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IOS swift 原始横向图片旋转为竖向旋转

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