Question

我遵循old tutorial设置数据结构以查看图像中的RGBA值。在过去大部分时间里，所有数据用尽了，但我遇到了一个看起来非常简单的问题，我才刚刚起步，所以事实证明它要困难一些。

import UIKit

public struct RGBAPixel {
    public init(rawVal : UInt32) {
        raw = rawVal
    }
    public var raw: UInt32
    public var red: UInt8 {
        get { return UInt8(raw & 0xFF) }
        set { raw = UInt32(newValue) | (raw & 0xFFFFFF00) }
    }
    public var green: UInt8 {
        get { return UInt8( (raw & 0xFF00) >> 8) }
        set { raw = (UInt32(newValue) << 8) | (raw & 0xFFFF00FF) }
    }
    public var blue: UInt8 {
        get { return UInt8( (raw & 0xFF0000) >> 16) }
        set { raw = (UInt32(newValue) << 16) | (raw & 0xFF00FFFF) }
    }
    public var alpha: UInt8 {
        get { return UInt8( (raw & 0xFF000000) >> 24) }
        set { raw = (UInt32(newValue) << 24) | (raw & 0x00FFFFFF) }
    }
}

let image = UIImage(named: "crossSection.jpg")

let height = Int((image?.size.height)!)
let width = Int((image?.size.width)!)
let bitsPerComponent = Int(8)
let bytesPerRow = 4 * width
let colorSpace = CGColorSpaceCreateDeviceRGB()
let rawData = UnsafeMutablePointer<UInt32>.allocate(capacity: width * height)
let bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue | CGImageAlphaInfo.premultipliedLast.rawValue
let CGPointZero = CGPoint(x: 0,y: 0)
let rect = CGRect(origin: CGPointZero, size: (image?.size)!)

let imageContext = CGContext(data: rawData, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo)

imageContext?.draw(image!.cgImage!, in:rect)

let pixels = UnsafeMutableBufferPointer<UInt32>(start: rawData, count: width * height)

///*
for var y in 0 ..< height {
    for var x in 0 ..< width {
        var p = pixels[x+y*width] = RGBAPixel(rawVal: 0)
        p.red = 255
        pixels[x+y*width] = p


    }
}
//*/

let outContext = CGContext(data: pixels.baseAddress, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo)

let outImage = UIImage(cgImage: outContext!.makeImage()!)

有两个问题。首先是快速进入底部时的问题，它给出错误“无法将'RGBAPixel'类型的值分配给'UInt32'类型”。我很好地遵循了video，并找到了我似乎找不到的任何错误。看来这个问题不是更新带来的，所以我很困惑。我研究了结构和初始化，并且代码编写的方式似乎很有意义。初始化允许数据类型UInt32通过RGBAPixel传入。再说一次，非常新，所以请纠正我哪里我错了。谢谢

Answer 1

您使用的是<UInt32>而不是<RGBAPixel>

let rawData = UnsafeMutablePointer<UInt32>.allocate(capacity: width * height)
//Should be:
let rawData = UnsafeMutablePointer<RGBAPixel>.allocate(capacity: width * height)

与：

let pixels = UnsafeMutableBufferPointer<UInt32>(start: rawData, count: width * height)
// Should be:
let pixels = UnsafeMutableBufferPointer<RGBAPixel>(start: rawData, count: width * height)

尝试一下（为便于阅读，我添加了一些空白行）-使用黑色作为颜色：

import UIKit

struct RGBAPixel {
    var raw: UInt32

    public init(rawVal : UInt32) {
        raw = rawVal
    }

    public var red: UInt8 {
        get { return UInt8(raw & 0xFF) }
        set { raw = UInt32(newValue) | (raw & 0xFFFFFF00) }
    }

    public var green: UInt8 {
        get { return UInt8( (raw & 0xFF00) >> 8) }
        set { raw = (UInt32(newValue) << 8) | (raw & 0xFFFF00FF) }
    }

    public var blue: UInt8 {
        get { return UInt8( (raw & 0xFF0000) >> 16) }
        set { raw = (UInt32(newValue) << 16) | (raw & 0xFF00FFFF) }
    }

    public var alpha: UInt8 {
        get { return UInt8( (raw & 0xFF000000) >> 24) }
        set { raw = (UInt32(newValue) << 24) | (raw & 0x00FFFFFF) }
    }
}

let image = UIImage(named: "crossSection.jpg")

let height = Int((image?.size.height)!)
let width = Int((image?.size.width)!)

let bitsPerComponent = Int(8)
let bytesPerRow = 4 * width

let colorSpace = CGColorSpaceCreateDeviceRGB()

let rawData = UnsafeMutablePointer<RGBAPixel>.allocate(capacity: width * height)

let bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue | CGImageAlphaInfo.premultipliedLast.rawValue

let CGPointZero = CGPoint(x: 0,y: 0)

let rect = CGRect(origin: CGPointZero, size: (image?.size)!)

let imageContext = CGContext(data: rawData, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo)

imageContext?.draw(image!.cgImage!, in:rect)

let pixels = UnsafeMutableBufferPointer<RGBAPixel>(start: rawData, count: width * height)

///*
for var y in 0 ..< height {
    for var x in 0 ..< width {
        pixels[x+y*width] = RGBAPixel(rawVal: 0xFF000000)
    }
}
//*/

let outContext = CGContext(data: pixels.baseAddress, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo)

let outImage = UIImage(cgImage: outContext!.makeImage()!)

要使用颜色：

for var y in 0 ..< height {
    for var x in 0 ..< width {
        var p = RGBAPixel(rawVal: 0xFF000000)
        p.red = 128
        pixels[x+y*width] = p
    }
}

值类型和初始化的问题

1 个答案: