Task: Julia set
C++: #include <windows.h>
#include <string>
#include <complex>

const int BMP_SIZE = 600, ITERATIONS = 512;
const long double FCT = 2.85, hFCT = FCT / 2.0;

class myBitmap {
public:
    myBitmap() : pen( NULL ), brush( NULL ), clr( 0 ), wid( 1 ) {}
    ~myBitmap() {
        DeleteObject( pen ); DeleteObject( brush );
        DeleteDC( hdc ); DeleteObject( bmp );
    }
    bool create( int w, int h ) {
        BITMAPINFO bi;
        ZeroMemory( &bi, sizeof( bi ) );
        bi.bmiHeader.biSize        = sizeof( bi.bmiHeader );
        bi.bmiHeader.biBitCount    = sizeof( DWORD ) * 8;
        bi.bmiHeader.biCompression = BI_RGB;
        bi.bmiHeader.biPlanes      = 1;
        bi.bmiHeader.biWidth       =  w;
        bi.bmiHeader.biHeight      = -h;
        HDC dc = GetDC( GetConsoleWindow() );
        bmp = CreateDIBSection( dc, &bi, DIB_RGB_COLORS, &pBits, NULL, 0 );
        if( !bmp ) return false;
        hdc = CreateCompatibleDC( dc );
        SelectObject( hdc, bmp );
        ReleaseDC( GetConsoleWindow(), dc );
        width = w; height = h;
        return true;
    }
    void clear( BYTE clr = 0 ) {
        memset( pBits, clr, width * height * sizeof( DWORD ) );
    }
    void setBrushColor( DWORD bClr ) {
        if( brush ) DeleteObject( brush );
        brush = CreateSolidBrush( bClr );
        SelectObject( hdc, brush );
    }
    void setPenColor( DWORD c ) {
        clr = c; createPen();
    }
    void setPenWidth( int w ) {
        wid = w; createPen();
    }
    void saveBitmap( std::string path ) {
        BITMAPFILEHEADER fileheader;
        BITMAPINFO       infoheader;
        BITMAP           bitmap;
        DWORD            wb;
        GetObject( bmp, sizeof( bitmap ), &bitmap );
        DWORD* dwpBits = new DWORD[bitmap.bmWidth * bitmap.bmHeight];
        ZeroMemory( dwpBits, bitmap.bmWidth * bitmap.bmHeight * sizeof( DWORD ) );
        ZeroMemory( &infoheader, sizeof( BITMAPINFO ) );
        ZeroMemory( &fileheader, sizeof( BITMAPFILEHEADER ) );
        infoheader.bmiHeader.biBitCount = sizeof( DWORD ) * 8;
        infoheader.bmiHeader.biCompression = BI_RGB;
        infoheader.bmiHeader.biPlanes = 1;
        infoheader.bmiHeader.biSize = sizeof( infoheader.bmiHeader );
        infoheader.bmiHeader.biHeight = bitmap.bmHeight;
        infoheader.bmiHeader.biWidth = bitmap.bmWidth;
        infoheader.bmiHeader.biSizeImage = bitmap.bmWidth * bitmap.bmHeight * sizeof( DWORD );
        fileheader.bfType    = 0x4D42;
        fileheader.bfOffBits = sizeof( infoheader.bmiHeader ) + sizeof( BITMAPFILEHEADER );
        fileheader.bfSize    = fileheader.bfOffBits + infoheader.bmiHeader.biSizeImage;
        GetDIBits( hdc, bmp, 0, height, ( LPVOID )dwpBits, &infoheader, DIB_RGB_COLORS );
        HANDLE file = CreateFile( path.c_str(), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, 
            FILE_ATTRIBUTE_NORMAL, NULL );
        WriteFile( file, &fileheader, sizeof( BITMAPFILEHEADER ), &wb, NULL );
        WriteFile( file, &infoheader.bmiHeader, sizeof( infoheader.bmiHeader ), &wb, NULL );
        WriteFile( file, dwpBits, bitmap.bmWidth * bitmap.bmHeight * 4, &wb, NULL );
        CloseHandle( file );
        delete [] dwpBits;
    }
    HDC getDC() const     { return hdc; }
    int getWidth() const  { return width; }
    int getHeight() const { return height; }
    DWORD* bits() const { return ( DWORD* )pBits; }
private:
    void createPen() {
        if( pen ) DeleteObject( pen );
        pen = CreatePen( PS_SOLID, wid, clr );
        SelectObject( hdc, pen );
    }
    HBITMAP bmp; HDC    hdc;
    HPEN    pen; HBRUSH brush;
    void    *pBits; int    width, height, wid;
    DWORD    clr;
};
class julia {
public:
    void draw( std::complex<long double> k ) {
        bmp.create( BMP_SIZE, BMP_SIZE );
        DWORD* bits = bmp.bits();
        int res, pos;
        std::complex<long double> c, factor( FCT / BMP_SIZE, FCT / BMP_SIZE ) ;

        for( int y = 0; y < BMP_SIZE; y++ ) {
            pos = y * BMP_SIZE;

            c.imag( ( factor.imag() * y ) + -hFCT );

            for( int x = 0; x < BMP_SIZE; x++ ) {
                c.real( factor.real() * x + -hFCT );
                res = inSet( c, k );
                if( res ) {
                    int n_res = res % 255;
                    if( res < ( ITERATIONS >> 1 ) ) res = RGB( n_res << 2, n_res << 3, n_res << 4 );
                    else res = RGB( n_res << 4, n_res << 2, n_res << 5 );
                }
                bits[pos++] = res;
            }
        }
        bmp.saveBitmap( "./js.bmp" );
    }
private:
    int inSet( std::complex<long double> z, std::complex<long double> c ) {
        long double dist;
        for( int ec = 0; ec < ITERATIONS; ec++ ) {
            z = z * z; z = z + c;
            dist = ( z.imag() * z.imag() ) + ( z.real() * z.real() );
            if( dist > 3 ) return( ec );
        }
        return 0;
    }
    myBitmap bmp;
};
int main( int argc, char* argv[] ) {
    std::complex<long double> c;
    long double factor = FCT / BMP_SIZE;
    c.imag( ( factor * 184 ) + -1.4 );
    c.real( ( factor * 307 ) + -2.0 );
    julia j; j.draw( c ); return 0;    
}

Go: package main

import (
	"image"
	"image/color"
	"image/png"
	"log"
	"os"
	"sync"
)

func main() {
	const (
		width, height = 800.0, 600.0
		maxIter       = 255
		cX, cY        = -0.7, 0.27015
		fileName      = "julia.png"
	)
	img := image.NewNRGBA(image.Rect(0, 0, width, height))

	var wg sync.WaitGroup
	wg.Add(width)
	for x := 0; x < width; x++ {
		thisx := float64(x)
		go func() {
			var tmp, zx, zy float64
			var i uint8
			for y := 0.0; y < height; y++ {
				zx = 1.5 * (thisx - width/2) / (0.5 * width)
				zy = (y - height/2) / (0.5 * height)
				i = maxIter
				for zx*zx+zy*zy < 4.0 && i > 0 {
					tmp = zx*zx - zy*zy + cX
					zy = 2.0*zx*zy + cY
					zx = tmp
					i--
				}
				img.Set(int(thisx), int(y), color.RGBA{i, i, i << 3, 255})
			}
			wg.Done()
		}()
	}
	wg.Wait()
	imgFile, err := os.Create(fileName)
	if err != nil {
		log.Fatal(err)
	}
	defer imgFile.Close()
	if err := png.Encode(imgFile, img); err != nil {
		imgFile.Close()
		log.Fatal(err)
	}
}