给我用C++生成影像金字塔的代码

以下是使用C语言生成影像金字塔的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"

#define MAX_LEVELS 10

typedef struct {
    unsigned char *data;
    int width, height, channels;
} Image;

Image load_image(char *filename) {
    Image img;
    img.data = stbi_load(filename, &img.width, &img.height, &img.channels, 0);
    return img;
}

void free_image(Image *img) {
    if (img->data) {
        stbi_image_free(img->data);
        img->data = NULL;
    }
    img->width = img->height = img->channels = 0;
}

void save_image(char *filename, Image img) {
    stbi_write_png(filename, img.width, img.height, img.channels, img.data, img.width * img.channels);
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s input_image\n", argv[0]);
        return 1;
    }

    Image src = load_image(argv[1]);
    if (!src.data) {
        fprintf(stderr, "Error: cannot load image '%s'\n", argv[1]);
        return 1;
    }

    Image pyr[MAX_LEVELS];
    pyr[0] = src;

    int levels = 1;
    while (levels < MAX_LEVELS) {
        Image prev = pyr[levels - 1];
        Image next;
        next.width = prev.width / 2;
        next.height = prev.height / 2;
        next.channels = prev.channels;
        next.data = malloc(next.width * next.height * next.channels);

        for (int i = 0; i < next.height; i++) {
            for (int j = 0; j < next.width; j++) {
                for (int k = 0; k < next.channels; k++) {
                    int idx = (i * 2) * prev.width * prev.channels + (j * 2) * prev.channels + k;
                    next.data[i * next.width * next.channels + j * next.channels + k] = prev.data[idx];
                }
            }
        }

        pyr[levels] = next;
        levels++;

        if (next.width < 2 || next.height < 2) {
            break;
        }
    }

    for (int i = 0; i < levels; i++) {
        char filename[256];
        sprintf(filename, "level_%d.png", i);
        save_image(filename, pyr[i]);
    }

    for (int i = 0; i < levels; i++) {
        free_image(&pyr[i]);
    }

    free_image(&src);

    return 0;
}

这个程序可以读取一个图像文件，然后生成一组影像金字塔图像，每一层的分辨率是上一层的一半。在程序中，我们使用了stb_image和stb_image_write库来读取和写入图像文件。请注意，这个程序只支持处理RGB图像，如果需要处理其他类型的图像，需要进行一些修改。