在swift中从UIImage / CGImage获取像素数据作为数组

问题描述

限时删除！！

到目前为止，我有一个应用程序允许用户在UIImageView元素上自由绘制（如草图板）。

I have an app so far that allows the user to free draw (like a sketch pad) on a UIImageView element.

我想获取原始RGB像素数据（作为0到255整数值）作为多维数组，因此我可以将其提供给机器学习算法。或者是否有其他方法可以将原始图像数据发送到单独的C ++函数？

I want to get the raw RGB pixel data (as 0 to 255 integer values) as a multidimensional array so I can feed it into a machine learning algorithm . Or is there some other way I can send the raw image data over to separate C++ function?

在Swift中有一种简单的方法吗？

Is there an easy way to do this in Swift?

推荐答案

将CGImage转换为强度值数组

我的函数需要 CGImage 并返回无符号8位整数数组以及图像的宽度和高度。我写了这段代码用于灰度图像。将其扩展为颜色应该是将Gray更改为RGB并将每像素的字节数更改为3，假设没有alpha通道。

Converting a CGImage to an array of intensity values

My function takes a CGImage and returns an array of unsigned 8-bit integers as well as the width and height of the image. I wrote this code for use with grayscale images. Extending this to color should be a matter of changing Gray to RGB and changing the bytes per pixel to 3 assuming no alpha channel.

func pixelValues(fromCGImage imageRef: CGImage?) -> (pixelValues: [UInt8]?, width: Int, height: Int)
{
    var width = 0
    var height = 0
    var pixelValues: [UInt8]?
    if let imageRef = imageRef {
        width = imageRef.width
        height = imageRef.height
        let bitsPerComponent = imageRef.bitsPerComponent
        let bytesPerRow = imageRef.bytesPerRow
        let totalBytes = height * bytesPerRow

        let colorSpace = CGColorSpaceCreateDeviceGray()
        var intensities = [UInt8](repeating: 0, count: totalBytes)

        let contextRef = CGContext(data: &intensities, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: 0)
        contextRef?.draw(imageRef, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(width), height: CGFloat(height)))

        pixelValues = intensities
    }

    return (pixelValues, width, height)
}

func image(fromPixelValues pixelValues: [UInt8]?, width: Int, height: Int) -> CGImage?
{
    var imageRef: CGImage?
    if var pixelValues = pixelValues {
        let bitsPerComponent = 8
        let bytesPerPixel = 1
        let bitsPerPixel = bytesPerPixel * bitsPerComponent
        let bytesPerRow = bytesPerPixel * width
        let totalBytes = height * bytesPerRow

        imageRef = withUnsafePointer(to: &pixelValues, {
            ptr -> CGImage? in
            var imageRef: CGImage?
            let colorSpaceRef = CGColorSpaceCreateDeviceGray()
            let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue).union(CGBitmapInfo())
            let data = UnsafeRawPointer(ptr.pointee).assumingMemoryBound(to: UInt8.self)
            let releaseData: CGDataProviderReleaseDataCallback = {
                (info: UnsafeMutableRawPointer?, data: UnsafeRawPointer, size: Int) -> () in
            }

            if let providerRef = CGDataProvider(dataInfo: nil, data: data, size: totalBytes, releaseData: releaseData) {
                imageRef = CGImage(width: width,
                                   height: height,
                                   bitsPerComponent: bitsPerComponent,
                                   bitsPerPixel: bitsPerPixel,
                                   bytesPerRow: bytesPerRow,
                                   space: colorSpaceRef,
                                   bitmapInfo: bitmapInfo,
                                   provider: providerRef,
                                   decode: nil,
                                   shouldInterpolate: false,
                                   intent: CGColorRenderingIntent.defaultIntent)
            }

            return imageRef
        })
    }

    return imageRef
}

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