C++如何使用指针数组缩小图像

我正在编写一个处理图像的 c++ 程序，这是缩小图像的函数。 有一个"像素"指针数组和一个定义了图像颜色的类。 除了Visual Studio中包含的库之外，我不能使用任何其他库进行此图像程序。 我对此功能有问题，我需要遍历图像中的像素并将其拆分为块;用户将输入块的宽度/高度。 创建块后，需要从每个块中获取平均RGB值（该平均值将成为单个新像素），并且所有块的排列都将"缩小"图像。 到目前为止，似乎创建块是因为图像变小，但我的图像完全变成灰色。RGB 像素的总数正确添加，但代码的其余部分必须关闭某些内容，我无法确定它。这是我的代码：

//creates a block of average colors based on range of pixels given
pixel CreateBlock(int start, int stop, pixel** currpix, int blockHeight, int blockWidth)
{
    pixel** block;          //Problem? might have to be a single pointer pixel* block[];
    block = new pixel*[blockHeight];
    for (int i = 0; i < blockHeight; i++)
        block[i] = new pixel[blockWidth];
    pixel newPix;
    float totred = 0, totblue = 0, totgreen = 0;
    int redav = 0.0, blueav = 0.0, greenav = 0.0;
    for (int i = 0; i < blockHeight; i++)
    {
        for (int j = 0; j < blockWidth; j++)
        {
            totred = totred + block[i][j].red;
            totblue = totblue + block[i][j].blue;
            totgreen = totgreen + block[i][j].green;
        }
    }
    redav = totred / (blockHeight*blockWidth);
    blueav = totblue / (blockHeight* blockWidth);
    greenav = totgreen / (blockHeight*blockWidth);
    newPix.red = redav;
    newPix.blue = blueav;
    newPix.green = greenav;
    return newPix;
}
//make a new image that is a smaller resampling of the bigger image
void averageRegions(int blockWidth, int blockHeight)
{
    int height = displayed->getHeight(), width = displayed->getWidth();
    int i = 0, j = 0;
    pixel** currpix = displayed->getPixels();           //PROBLEM
    image* shrunk = displayed;
    //shrunk->getPixels();
    shrunk->createNewImage(width / blockWidth, height / blockHeight);
    while (i < height)
    {
        while (j < width)
        {
            int start = i, stop = i + 10;
            shrunk->getPixels()[i][j] = CreateBlock(start, stop, currpix, blockHeight, blockWidth);
            j = j + blockWidth;
        }
        i = i + blockHeight;
    }
    return;
}

下面是图像类：

class image {
    public:
        image();            //the image constructor (initializes everything)
        image(string filename);  //a image constructor that directly loads an image from disk
        ~image();           //the image destructor  (deletes the dynamically created pixel array)
        void createNewImage(int width, int height); //this function deletes any current image data and creates a new blank image
                                                //with the specified width/height and allocates the needed number of pixels
                                                //dynamically.
        bool loadImage(string filename);        //load an image from the specified file path.  Return true if it works, false if it is not a valid image.
                                            //Note that we only accept images of the RGB 8bit colorspace!
        void saveImage(string filename);       //Save an image to the specified path
        pixel** getPixels();                    //return the 2-dimensional pixels array
        int getWidth();                     //return the width of the image
        int getHeight();                    //return the height of the image
        void viewImage(CImage* myImage);  //This function is called by the windows GUI.  It returns the image in format the GUI understands.

    private:
        void pixelsToCImage(CImage* myImage);  //this function is called internally by the image class.
                                            //it converts our pixel struct array to a standard BGR uchar array with word spacing.
                                            //(Don't worry about what this does)
        pixel** pixels;             // pixel data array for image 
        int width, height;      // stores the image dimensions 
};

这是像素类：

class pixel
{
public:
    unsigned char red;      //the red component
    unsigned char green;    //the green component
    unsigned char blue;     //the blue component
};