Contents

separableConvolve(horizontalKernel:verticalKernel:bias:edgeMode:destination:)

Performs separable convolution on a multiple plane 32-bit pixel buffer.

Declaration

func separableConvolve(horizontalKernel: [Float], verticalKernel: [Float], bias: Float = 0, edgeMode: vImage.EdgeMode<Pixel_F>, destination: vImage.PixelBuffer<Format>)

Parameters

  • horizontalKernel:

    The 1D horizontal convolution kernel.

  • verticalKernel:

    The 1D vertical convolution kernel.

  • bias:

    A value that the operation adds to each element in the convolution result, before performing any clipping.

  • edgeMode:

    The convolution edge mode. The background color must be a single Pixel_f value.

  • destination:

    The destination pixel buffer.

Discussion

The following code shows how to generate a multiplane pixel buffer from a CGImage instance and apply a Gaussian blur using separable convolution:

let srcImage =  imageLiteral(resourceName: " ... ").cgImage(
    forProposedRect: nil,
    context: nil,
    hints: nil)!

var cgImageFormat = vImage_CGImageFormat(
    bitsPerComponent: 32,
    bitsPerPixel: 32 * 3,
    colorSpace: CGColorSpaceCreateDeviceRGB(),
    bitmapInfo: CGBitmapInfo(rawValue:kCGBitmapByteOrder32Host.rawValue |
                             CGBitmapInfo.floatComponents.rawValue |
                             CGImageAlphaInfo.none.rawValue))!

let interleavedBuffer = try vImage.PixelBuffer(
    cgImage: srcImage,
    cgImageFormat: &cgImageFormat,
    pixelFormat: vImage.InterleavedFx3.self)

let multiplaneSrcBuffer = vImage.PixelBuffer<vImage.PlanarFx3>(
    interleavedBuffer: interleavedBuffer)

let multiplaneDestBuffer = vImage.PixelBuffer<vImage.PlanarFx3>(
    size: multiplaneSrcBuffer.size)

multiplaneSrcBuffer.separableConvolve(
    horizontalKernel: vImage.ConvolutionKernel.gaussian1Dx7,
    verticalKernel:  vImage.ConvolutionKernel.gaussian1Dx7,
    edgeMode: .truncateKernel,
    destination: multiplaneDestBuffer)

multiplaneDestBuffer.convert(to: interleavedBuffer)

let outputImage = interleavedBuffer.makeCGImage(cgImageFormat: cgImageFormat)

See Also

Related Documentation

Separable convolution