我们如何使用 C 将位图图像转换为 ASCII 艺术，同时尊重灰度图像、等宽字体和初学者的简单性等约束？

<code class="cpp">#include <iostream>
#include <vector>

using namespace std;

// Character map with precomputed intensities
const char charMap[] = " .,:;ox%#@";

// Convert an image to ASCII art
string imageToASCIIArt(const vector<vector<int>>& image) {
  // Compute the intensity map
  vector<int> intensityMap(image.size() * image[0].size());
  for (size_t y = 0; y < image.size(); y++) {
    for (size_t x = 0; x < image[0].size(); x++) {
      intensityMap[y * image[0].size() + x] = image[y][x];
    }
  }

  // Replace each pixel with a character from the character map
  string asciiArt;
  for (int intensity : intensityMap) {
    asciiArt += charMap[intensity / 255 * (sizeof(charMap) - 1)];
  }

  return asciiArt;
}

int main() {
  // Load image data into a vector of vectors
  vector<vector<int>> image = {
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    {0, 0, 0, 255, 255, 255, 255, 0, 0, 0},
    {0, 0, 0, 255, 255, 255, 255, 0, 0, 0},
    {0, 0, 0, 255, 255, 255, 255, 0, 0, 0},
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  };

  // Convert image to ASCII art and print
  string asciiArt = imageToASCIIArt(image);
  cout << asciiArt << endl;

  return 0;
}</code>