iOS - 快速创建无符号字符

Posted 2023-02-16

【中文标题】iOS - 快速创建无符号字符

【英文标题】：iOS - create unsigned char in swift

【发布时间】：2017-05-23 23:27:56

【问题描述】：

我正在将一些 Objective-C 代码转换为 Swift，其中包含以下代码：

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char rgba[4];
CGContextRef context = CGBitmapContextCreate(rgba, 1, 1, 8, 4, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

CGContextDrawImage(context, CGRectMake(0, 0, 1, 1), image.CGImage);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);


UIColor *averageColor = [UIColor colorWithRed:((CGFloat)rgba[0])/255.0 green:((CGFloat)rgba[1])/255.0 blue:((CGFloat)rgba[2])/255.0 alpha:alpha];
averageColor = [averageColor colorWithMinimumSaturation:0.15];

我已经设法轻松转换颜色空间，但如何在 Swift 3 中创建无符号字符？

我尝试了以下，但编译器提示以下错误：

Cannot convert value of type '[CUnsignedChar]' to expected argument type 'UnsafeMutableRawPointer?'

这是代码：

 let colorSpace: CGColorSpace = CGColorSpaceCreateDeviceRGB()
 let rgba = [CUnsignedChar](repeating: 0,count: 4)
 // error on this line because of the rgba     
 let context: CGContext = CGContext.init(data: rgba, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast | CGBitmapInfo.byteOrder32Big) 


context.draw(image.cgImage!, in: CGRect(x: 0, y: 0, width: 1, height: 1))

我不能再继续下去了

有人可以帮忙吗？

谢谢

【参考方案1】：

试试这个..

let colorSpace: CGColorSpace = CGColorSpaceCreateDeviceRGB()
let data = UnsafeMutableRawPointer.allocate(bytes: 4, alignedTo: 1) // 4 unsigned char = 4 bytes
let context: CGContext = CGContext.init(data: data, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast | CGBitmapInfo.byteOrder32Big)
let rgba = Array(UnsafeBufferPointer(start: data.assumingMemoryBound(to: UInt8.self), count: 4))
//  .... other 

【讨论】：

奇怪的是，这是我从***.com/a/29403023/1214800 翻译答案所需的确切代码?