真不敢相信这里竟然没有一个正确答案。不需要分配指针，未乘的值仍然需要规范化。开门见山地说，下面是Swift 4的正确版本。对于UIImage，只需使用。cgimage。

extension CGImage {
    func colors(at: [CGPoint]) -> [UIColor]? {
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bytesPerPixel = 4
        let bytesPerRow = bytesPerPixel * width
        let bitsPerComponent = 8
        let bitmapInfo: UInt32 = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Big.rawValue
    
        guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo),
            let ptr = context.data?.assumingMemoryBound(to: UInt8.self) else {
            return nil
        }
    
        context.draw(self, in: CGRect(x: 0, y: 0, width: width, height: height))
    
        return at.map { p in
            let i = bytesPerRow * Int(p.y) + bytesPerPixel * Int(p.x)
            
            let a = CGFloat(ptr[i + 3]) / 255.0
            let r = (CGFloat(ptr[i]) / a) / 255.0
            let g = (CGFloat(ptr[i + 1]) / a) / 255.0
            let b = (CGFloat(ptr[i + 2]) / a) / 255.0
            
            return UIColor(red: r, green: g, blue: b, alpha: a)
        }
    }
}

必须首先将图像绘制/转换为缓冲区的原因是，图像可以有几种不同的格式。需要此步骤将其转换为您可以读取的一致格式。

一种方法是将图像绘制到一个位图上下文中，这个位图上下文由给定的缓冲区支持，用于给定的颜色空间(在这种情况下是RGB):(注意，这将把图像数据复制到该缓冲区中，所以你想要缓存它，而不是每次你需要获取像素值时都做这个操作)

请看下面的例子:

// First get the image into your data buffer
CGImageRef image = [myUIImage CGImage];
NSUInteger width = CGImageGetWidth(image);
NSUInteger height = CGImageGetHeight(image);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = malloc(height * width * 4);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);

CGContextDrawImage(context, CGRectMake(0, 0, width, height));
CGContextRelease(context);

// Now your rawData contains the image data in the RGBA8888 pixel format.
int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel;
red = rawData[byteIndex];
green = rawData[byteIndex + 1];
blue = rawData[byteIndex + 2];
alpha = rawData[byteIndex + 3];

这是一个SO线程，其中@Matt通过替换图像只渲染所需的像素到1x1上下文，以便所需的像素与上下文中的一个像素对齐。

Apple的技术问答QA1509展示了以下简单的方法:

CFDataRef CopyImagePixels(CGImageRef inImage)
{
    return CGDataProviderCopyData(CGImageGetDataProvider(inImage));
}

使用CFDataGetBytePtr来获得实际的字节(以及各种CGImageGet*方法来理解如何解释它们)。

仅供参考，我将凯雷姆克的答案与我的原始大纲结合起来，清除了错字，将其概括为返回一个颜色数组，并得到了整个编译。结果如下:

+ (NSArray*)getRGBAsFromImage:(UIImage*)image atX:(int)x andY:(int)y count:(int)count
{
    NSMutableArray *result = [NSMutableArray arrayWithCapacity:count];

    // First get the image into your data buffer
    CGImageRef imageRef = [image CGImage];
    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = (unsigned char*) calloc(height * width * 4, sizeof(unsigned char));
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                    bitsPerComponent, bytesPerRow, colorSpace,
                    kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    CGContextRelease(context);

    // Now your rawData contains the image data in the RGBA8888 pixel format.
    NSUInteger byteIndex = (bytesPerRow * y) + x * bytesPerPixel;
    for (int i = 0 ; i < count ; ++i)
    {
        CGFloat alpha = ((CGFloat) rawData[byteIndex + 3] ) / 255.0f;
        CGFloat red   = ((CGFloat) rawData[byteIndex]     ) / alpha;
        CGFloat green = ((CGFloat) rawData[byteIndex + 1] ) / alpha;
        CGFloat blue  = ((CGFloat) rawData[byteIndex + 2] ) / alpha;
        byteIndex += bytesPerPixel;

        UIColor *acolor = [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
        [result addObject:acolor];
    }

  free(rawData);

  return result;
}

基于Olie和Algal的回答，以下是Swift 3的最新答案

public func getRGBAs(fromImage image: UIImage, x: Int, y: Int, count: Int) -> [UIColor] {

var result = [UIColor]()

// First get the image into your data buffer
guard let cgImage = image.cgImage else {
    print("CGContext creation failed")
    return []
}

let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()
let rawdata = calloc(height*width*4, MemoryLayout<CUnsignedChar>.size)
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * width
let bitsPerComponent = 8
let bitmapInfo: UInt32 = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Big.rawValue

guard let context = CGContext(data: rawdata, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else {
    print("CGContext creation failed")
    return result
}

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

// Now your rawData contains the image data in the RGBA8888 pixel format.
var byteIndex = bytesPerRow * y + bytesPerPixel * x

for _ in 0..<count {
    let alpha = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 3, as: UInt8.self)) / 255.0
    let red = CGFloat(rawdata!.load(fromByteOffset: byteIndex, as: UInt8.self)) / alpha
    let green = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 1, as: UInt8.self)) / alpha
    let blue = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 2, as: UInt8.self)) / alpha
    byteIndex += bytesPerPixel

    let aColor = UIColor(red: red, green: green, blue: blue, alpha: alpha)
    result.append(aColor)
}

free(rawdata)

return result
}

斯威夫特