instructed/tilemap/examples/perlin_demo.cpp

#include "noise.h"
#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include <iomanip>

// Convert a noise value [0,1] to a grayscale color
std::string noise_to_grayscale(double noise_value) {
    // Clamp to [0,1] range
    noise_value = std::max(0.0, std::min(1.0, noise_value));
    
    // Convert to 0-255 range
    int gray = static_cast<int>(noise_value * 255);
    
    // Convert to hex color
    std::ostringstream oss;
    oss << "#" << std::hex << std::setfill('0') << std::setw(2) << gray
        << std::setw(2) << gray << std::setw(2) << gray;
    return oss.str();
}

// Generate SVG visualization of Perlin noise
void generate_noise_svg(const std::string& filename, int size, double scale, 
                       std::uint64_t seed, int octaves = 1, double persistence = 0.5) {
    std::ofstream file(filename);
    if (!file.is_open()) {
        std::cerr << "Error: Could not open output file: " << filename << std::endl;
        return;
    }
    
    // Create noise generator
    istd::PerlinNoise noise(seed);
    
    const int pixel_size = 2; // Size of each pixel in SVG units
    const int svg_size = size * pixel_size;
    
    // SVG header
    file << "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
    file << "<svg width=\"" << svg_size << "\" height=\"" << svg_size 
         << "\" xmlns=\"http://www.w3.org/2000/svg\">\n";
    file << "<title>Perlin Noise Visualization (Scale: " << scale 
         << ", Octaves: " << octaves << ", Seed: " << seed << ")</title>\n";
    
    // Generate noise values and create rectangles
    double min_value = 1.0, max_value = 0.0;
    
    for (int y = 0; y < size; ++y) {
        for (int x = 0; x < size; ++x) {
            double noise_value;
            if (octaves == 1) {
                noise_value = noise.noise(x * scale, y * scale);
            } else {
                noise_value = noise.octave_noise(x * scale, y * scale, octaves, persistence);
            }
            
            // Track min/max for statistics
            min_value = std::min(min_value, noise_value);
            max_value = std::max(max_value, noise_value);
            
            std::string color = noise_to_grayscale(noise_value);
            
            int svg_x = x * pixel_size;
            int svg_y = y * pixel_size;
            
            file << "<rect x=\"" << svg_x << "\" y=\"" << svg_y 
                 << "\" width=\"" << pixel_size << "\" height=\"" << pixel_size 
                 << "\" fill=\"" << color << "\"/>\n";
        }
    }
    
    // Add information text
    file << "<!-- Statistics: Min=" << min_value << " Max=" << max_value << " -->\n";
    
    // Add parameter info text overlay
    file << "<g transform=\"translate(10, 10)\">\n";
    file << "<rect x=\"0\" y=\"0\" width=\"300\" height=\"120\" fill=\"white\" stroke=\"black\" stroke-width=\"1\" opacity=\"0.9\"/>\n";
    file << "<text x=\"10\" y=\"20\" font-family=\"Arial\" font-size=\"14\" font-weight=\"bold\">Perlin Noise Parameters</text>\n";
    file << "<text x=\"10\" y=\"40\" font-family=\"Arial\" font-size=\"12\">Size: " << size << "x" << size << "</text>\n";
    file << "<text x=\"10\" y=\"55\" font-family=\"Arial\" font-size=\"12\">Scale: " << scale << "</text>\n";
    file << "<text x=\"10\" y=\"70\" font-family=\"Arial\" font-size=\"12\">Seed: " << seed << "</text>\n";
    file << "<text x=\"10\" y=\"85\" font-family=\"Arial\" font-size=\"12\">Octaves: " << octaves << "</text>\n";
    file << "<text x=\"10\" y=\"100\" font-family=\"Arial\" font-size=\"12\">Range: [" 
         << std::fixed << std::setprecision(3) << min_value << ", " << max_value << "]</text>\n";
    file << "</g>\n";
    
    // Add grayscale legend
    file << "<g transform=\"translate(" << (svg_size - 60) << ", 10)\">\n";
    file << "<text x=\"0\" y=\"15\" font-family=\"Arial\" font-size=\"12\" font-weight=\"bold\">Value</text>\n";
    for (int i = 0; i <= 10; ++i) {
        double value = i / 10.0;
        std::string color = noise_to_grayscale(value);
        int y_pos = 20 + i * 15;
        file << "<rect x=\"0\" y=\"" << y_pos << "\" width=\"20\" height=\"12\" fill=\"" 
             << color << "\" stroke=\"black\" stroke-width=\"0.5\"/>\n";
        file << "<text x=\"25\" y=\"" << (y_pos + 9) << "\" font-family=\"Arial\" font-size=\"10\">" 
             << std::fixed << std::setprecision(1) << value << "</text>\n";
    }
    file << "</g>\n";
    
    file << "</svg>\n";
    file.close();
    
    std::cout << "Perlin noise SVG generated: " << filename << std::endl;
    std::cout << "Size: " << size << "x" << size << " pixels" << std::endl;
    std::cout << "Scale: " << scale << ", Octaves: " << octaves << std::endl;
    std::cout << "Value range: [" << std::fixed << std::setprecision(3) 
              << min_value << ", " << max_value << "]" << std::endl;
}

int main(int argc, char* argv[]) {
    // Default parameters
    std::uint64_t seed = 12345;
    std::string output_filename = "perlin_noise.svg";
    double scale = 0.02;
    int octaves = 1;
    double persistence = 0.5;
    
    // Parse command line arguments
    if (argc >= 2) {
        seed = std::strtoull(argv[1], nullptr, 10);
    }
    if (argc >= 3) {
        output_filename = argv[2];
    }
    if (argc >= 4) {
        scale = std::strtod(argv[3], nullptr);
    }
    if (argc >= 5) {
        octaves = std::strtol(argv[4], nullptr, 10);
    }
    if (argc >= 6) {
        persistence = std::strtod(argv[5], nullptr);
    }
    
    if (argc == 1 || argc > 6) {
        std::cout << "Usage: " << argv[0] << " [seed] [output.svg] [scale] [octaves] [persistence]\n";
        std::cout << "Defaults: seed=12345, output=perlin_noise.svg, scale=0.02, octaves=1, persistence=0.5\n";
        std::cout << "Examples:\n";
        std::cout << "  " << argv[0] << " 54321 noise1.svg 0.01\n";
        std::cout << "  " << argv[0] << " 12345 octave_noise.svg 0.02 4 0.5\n";
        if (argc > 6) return 1;
    }
    
    // Validate parameters
    if (scale <= 0) {
        std::cerr << "Error: Scale must be positive\n";
        return 1;
    }
    if (octaves < 1 || octaves > 10) {
        std::cerr << "Error: Octaves must be between 1 and 10\n";
        return 1;
    }
    if (persistence <= 0 || persistence > 1) {
        std::cerr << "Error: Persistence must be between 0 and 1\n";
        return 1;
    }
    
    std::cout << "Generating 256x256 Perlin noise visualization..." << std::endl;
    std::cout << "Parameters: seed=" << seed << ", scale=" << scale 
              << ", octaves=" << octaves << ", persistence=" << persistence << std::endl;
    
    // Generate the noise visualization
    generate_noise_svg(output_filename, 256, scale, seed, octaves, persistence);
    
    return 0;
}