从 cgimage 获取位图答案

【问题标题】：getting bitmap from cgimage从 cgimage 获取位图
【发布时间】：2018-01-08 22:36:21
【问题描述】：

我正在尝试从 CGImage 获取位图数据并将其读入像素数组。但是，我的 imagecontext 和 imagecontext?.draw() 总是返回 nil。

let capturedimage = UIImage(named: "random.jpg")
let image = capturedimage?.cgImage
let width = Int((image?.width)!)
let height = Int((image?.height)!)
let bytesPerPixel = 4;
let bytesPerRow = bytesPerPixel * width;
let bitsPerComponent = 8;
let pixelArr: [[UInt32]] = Array(repeating: Array(repeating: 0, count: width), count: height)
let pointer: UnsafeMutableRawPointer = UnsafeMutableRawPointer(mutating: pixelArr);
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue
let imageContext = CGContext(data: pointer, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo);
imageContext?.draw(image!, in: CGRect(x: 0, y: 0, width:width, height:height))

我已经多次检查我的代码，但我不知道我哪里出错了。

【问题讨论】：

标签： swift cgimage

【解决方案1】：

let image = UIImage(named: "2.png")

guard let cgImage = image?.cgImage else {
    fatalError()
}

let width = cgImage.width
let height = cgImage.height

let bytesPerPixel = 4;
let bytesPerRow = bytesPerPixel * width;
let bitsPerComponent = 8;
let pixelsCount = width * height
let bitmapData: UnsafeMutablePointer<UInt32> = .allocate(capacity: pixelsCount)
defer {
    bitmapData.deallocate()
}
bitmapData.initialize(repeating: 0, count: pixelsCount)
var pixelAtPosition: ((Int, Int) -> UInt32) = { x, y in
    return bitmapData[y * width + x]
}

guard let context = CGContext(data: bitmapData, width: width, height: height,
                              bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow,
                              space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
                                fatalError()
}
//draw image to context
var rect = CGRect(x: 0, y: 0, width: width, height: height)
context.draw(cgImage, in: rect)

let traget = pixelAtPosition(200, 200)

print(String(format: "pixel 0x%08X", traget))
print(String(format: "red 0x%2X", (traget & 0x000000FF)))
print(String(format: "green 0x%2X", (traget & 0x0000FF00) >> 8))
print(String(format: "blue 0x%2X", (traget & 0x00FF0000) >> 16))
print(String(format: "alpha 0x%2X", (traget & 0xFF000000) >> 24))

【讨论】：