醉Mandelbrot实施

Question

我写了一个应该绘制Mandelbrot分形的程序。不幸的是，它似乎喝醉了。这是输出：

相关功能：

#include <memory>

struct ImageDeleter
{
    void operator()(void* ptr) const;
};

class Image
{
public: // but don't touch it
    std::unique_ptr<void, ImageDeleter> internal;
private:
    /* private operations on surface */
public:
    /* public operations */
    void save(const std::string& path) const;
    Image(int width, int height);
};

// EXAMPLE USAGE

// Image img(640, 480);
// img.save("aaa.bmp");

// IN THE DEFINITION FILE

#include <SDL2/SDL.h>

namespace detail
{
    SDL_Surface* as_surface(const Image& img)
    {
        return static_cast<SDL_Surface*>(img.internal.get());
    }
}

void ImageDeleter::operator()(void* ptr) const
{
    SDL_FreeSurface(static_cast<SDL_Surface*>(ptr));
}

Image::Image(int width, int height) :
    internal(SDL_CreateRGBSurface(0, width, height, 32, 0, 0, 0, 0))
{

}

void Image::save(const std::string& path) const
{
    SDL_SaveBMP(detail::as_surface(*this), path.c_str());
}

我相信void drawMandelbrot(float x, float y, float width, float height, float delta) { for (float currentX = -2; currentX < 2; currentX += delta) { for (float currentY = -2; currentY < 2; currentY += delta) { Complex z(0, 0); Complex c(currentX, currentY); int iterations = 0; do { z = z * z + c; ++iterations; } while (z.getAbsoluteValue() <= 2 && iterations < MANDELBROT_ITERATION_LIMIT); ALLEGRO_COLOR pixelColor; float pixelX = (currentX + 2) / 4 * width; float pixelY = (currentY + 2) / 4 * width; if (z.getAbsoluteValue() <= 2) { pixelColor = blackColor; // Commented because you might not want this much junk in your terminal //std::cout << "Stayed small! " << z.toString() << std::endl; } else { pixelColor = al_color_hsv(iterations / MANDELBROT_ITERATION_LIMIT, 1.0f, 1.0f); // idem //std::cout << "Blew up! " << z.toString() << std::endl; } al_draw_pixel(pixelX, pixelY, pixelColor); } } } 方法是正确的，我怀疑上述函数中存在逻辑错误。检查上面（注释的）std :: cout语句的输出时，输出中复数的绝对值确实小于2，但图像看起来并不像绘制的mandelbrot集。

错误的情况在哪里？

编辑历史记录中包含mcve。

Answer 1

您对复数模量的计算不正确。

float Complex::getAbsoluteValue() const {
    return sqrt(real * real + imaginary + imaginary);
}

您已删除帖子的这一部分，但应该说

float Complex::getAbsoluteValue() const {
    return sqrt(real * real + imaginary * imaginary);
}