在Swift 3中使用CGPoint从图像中获取像素颜色 [英] Getting Pixel Color from an Image using CGPoint in Swift 3

问题描述

我在Swift 3中尝试这个PixelExtractor类，得到一个错误;
无法使用类型'（UnsafeMutableRawPointer？）'的参数列表调用类型'UnsafePointer'的初始值设定项。

I am try this PixelExtractor class in Swift 3, get a error; Cannot invoke initializer for type 'UnsafePointer' with an argument list of type '(UnsafeMutableRawPointer?)'

class PixelExtractor: NSObject {

let image: CGImage
let context: CGContextRef?

var width: Int {
    get {
        return CGImageGetWidth(image)
    }
}

var height: Int {
    get {
        return CGImageGetHeight(image)
    }
}

init(img: CGImage) {
    image = img
    context = PixelExtractor.createBitmapContext(img)
}

class func createBitmapContext(img: CGImage) -> CGContextRef {

    // Get image width, height
    let pixelsWide = CGImageGetWidth(img)
    let pixelsHigh = CGImageGetHeight(img)

    let bitmapBytesPerRow = pixelsWide * 4
    let bitmapByteCount = bitmapBytesPerRow * Int(pixelsHigh)

    // Use the generic RGB color space.
    let colorSpace = CGColorSpaceCreateDeviceRGB()

    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    let bitmapData = malloc(bitmapByteCount)
    let bitmapInfo = CGBitmapInfo(rawValue:   CGImageAlphaInfo.PremultipliedFirst.rawValue)
    let size = CGSizeMake(CGFloat(pixelsWide), CGFloat(pixelsHigh))
    UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
    // create bitmap
    let context = CGBitmapContextCreate(bitmapData, pixelsWide, pixelsHigh, 8,
    bitmapBytesPerRow, colorSpace, bitmapInfo.rawValue)

    // draw the image onto the context
    let rect = CGRect(x: 0, y: 0, width: pixelsWide, height: pixelsHigh)
    CGContextDrawImage(context, rect, img)

    return context!
}

func colorAt(x x: Int, y: Int)->UIColor {

    assert(0<=x && x<width)
    assert(0<=y && y<height)

    let uncastedData = CGBitmapContextGetData(context)
    let data = UnsafePointer<UInt8>(uncastedData)

    let offset = 4 * (y * width + x)

    let alpha: UInt8 = data[offset]
    let red: UInt8 = data[offset+1]
    let green: UInt8 = data[offset+2]
    let blue: UInt8 = data[offset+3]

    let color = UIColor(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: CGFloat(alpha)/255.0)

    return color
}

}

修复此错误。

let data = UnsafePointer<UInt8>(uncastedData)

- >

let data = UnsafeRawPointer(uncastedData)

获取其他错误; '类型'UnsafeRawPointer？'没有下标成员'

Get other error; 'Type 'UnsafeRawPointer?' has no subscript members'

如何修改此错误？

推荐答案

当你的数据中有 UnsafeRawPointer 时，你可以这样写：

You can write something like this when you have an UnsafeRawPointer in your data:

    let alpha = data.load(fromByteOffset: offset, as: UInt8.self)
    let red = data.load(fromByteOffset: offset+1, as: UInt8.self)
    let green = data.load(fromByteOffset: offset+2, as: UInt8.self)
    let blue = data.load(fromByteOffset: offset+3, as: UInt8.self)

否则，你可以得到 UnsafeMutablePointer< ;来自 uncastedData 的UInt8> （假设它是 UnsafeMutableRawPointer ）：

Or else, you can get UnsafeMutablePointer<UInt8> from your uncastedData (assuming it's an UnsafeMutableRawPointer):

    let data = uncastedData.assumingMemoryBound(to: UInt8.self)

这篇关于在Swift 3中使用CGPoint从图像中获取像素颜色的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！