src/GDI-effects-main/hslshader1.cpp

#include <windows.h>
#include <MATH.h>

COLORREF COLORHSL(int length) {
    double h = fmod(length, 360.0);
    double s = 1.0;
    double l = 0.5;

    double c = (1.0 - fabs(2.0 * l - 1.0)) * s;
    double x = c * (1.0 - fabs(fmod(h / 60.0, 2.0) - 1.0));
    double m = l - c / 2.0;

    double r1, g1, b1;
    if (h < 60) {
        r1 = c;
        g1 = x;
        b1 = 0;
    }
    else if (h < 120) {
        r1 = x;
        g1 = c;
        b1 = 0;
    }
    else if (h < 180) {
        r1 = 0;
        g1 = c;
        b1 = x;
    }
    else if (h < 240) {
        r1 = 0;
        g1 = x;
        b1 = c;
    }
    else if (h < 300) {
        r1 = x;
        g1 = 0;
        b1 = c;
    }
    else {
        r1 = c;
        g1 = 0;
        b1 = x;
    }

    int red = static_cast<int>((r1 + m) * 255);
    int green = static_cast<int>((g1 + m) * 255);
    int blue = static_cast<int>((b1 + m) * 255);

    return RGB(red, green, blue);
}

typedef union COLOR {
    COLORREF rgb;
    struct {
        BYTE blue;
        BYTE green;
        BYTE red;
    };
} COLOR;

DWORD WINAPI shader4(LPVOID lpParam) {
    int x = GetSystemMetrics(SM_CXSCREEN);
    int y = GetSystemMetrics(SM_CYSCREEN);
    int j = 1;
    int c = 0;

    COLOR* data = (COLOR*)VirtualAlloc(0, (x * y + x) * sizeof(COLOR), MEM_COMMIT, PAGE_READWRITE);
    HDC hdc = GetDC(0);
    HDC mdc = CreateCompatibleDC(hdc);
    HBITMAP bmp = CreateBitmap(x, y, 1, 32, data);
    SelectObject(mdc, bmp);

    while (true) {
        BitBlt(mdc, 0, 0, x, y, hdc, 0, 0, SRCCOPY);
        GetBitmapBits(bmp, x * y * sizeof(COLOR), data);

        for (int x2 = 0; x2 < x; x2++) {
            for (int y2 = 0; y2 < y; y2++) {
                int j = c * 4;

                int wave = (int)(j + (j * cbrt(((x2 * x2) - (y2 * y2)) / 64)));

                data[y2 * x + x2].rgb = COLORHSL((x * y) + wave);
            }
        }
        c++;

        SetBitmapBits(bmp, x * y * sizeof(COLOR), data);
        BitBlt(hdc, 0, 0, x, y, mdc, 0, 0, SRCCOPY);

        Sleep(10);
    }
}

int main() {
    CreateThread(0, 0, shader4, 0, 0, 0);
    Sleep(-1);
    return 0;
}