Generation of fractal images (C ++)

Recently, I saw the Delphi Program for a lifetime of component graphics on the Internet. The generated graphics are very beautiful, so I changed it to C ++ and improved the generation efficiency.
The Code is as follows (the original code uses the plural operation and is removed for efficiency, but is still kept in the comment)
// This function is used to obtain the color. S is between [0, 1] and the color is continuous.
Colorref getcolor (double S)
{
Int R, G, B;
If (s <= 0.25)
{
G = int (255 * s/0.25 );
Returns RGB (0, G, 255 );
}
Else if (S> 0.25 & S <= 0.5)
{
B = 255-int (255*(s-0.25)/0.25 );
Return RGB (0,255, B );
}
Else if (S> 0.5 & S <= 0.75)
{
R = int (255*(s-0.5)/0.25 );
Return RGB (R, 255, 0 );
}
Else
{
G = 255-int (255*(s-0.75)/0.25 );
Return RGB (255, G, 0 );
}
}

//////////////////////////////////////// /////////////////////////////////////
// Cmyview drawing

Void cmyview: ondraw (CDC * PDC)
{
Cmydoc * pdoc = getdocument ();
Complex <float> C, Z;
Float Cr, CI, Zr, Zi, PR, PI;
Int I, J, K;
Colorref color [256];
For (I = 0; I <256; I ++)
{
Color [I] = getcolor (I/256.0 );
}
Int Cx = 610, Cy = 511;
Byte * Data = new byte [CX * 4 * Cy];
Memset (data, 205, CX * 4 * CY );
// C = complex <float> (0.45,-0.1428 );
// C = complex <float> (-0.75, 0.0 );
// C = complex <float> (0.285, 0.0 );
// C = complex <float> (-0.8, 0.156 );
// C = complex <float> (-0.70176,-0.3842 );
// C = complex <float> (0.285, 0.01 );
// You can change the initial value to get different results.
Cr = 0.285f;
Ci = 0.01f;
For (I =-300; I <= 300; I ++)
{
For (j =-255; j <= 255; j ++)
{
// Z = complex <float> (I/255.0f, J/255.0f );
ZR = I/255.0f;
Zi = J/255.0f;
For (k = 0; k <= 255; k ++)
{
// If (SQRT (Z. Real () * z. Real () + Z. imag () * z. imag ()> 2.0)
If (SQRT (Zr * zR + Zi * zi)/2> 2.0)
{
Break;
}
Else
{
// Z = z * z + C;
PR = Zr * Zr-zi * Zi;
Pi = 2.0f * Zr * Zi;
ZR = Pr + CR;
Zi = PI + ci;
}
}
Data [4 * (CX * (cy-j-255) + I + 300)] = getbvalue (color [k]);
Data [4 * (CX * (cy-j-255) + I + 300) + 1] = getgvalue (color [k]);
Data [4 * (CX * (cy-j-255) + I + 300) + 2] = getrvalue (color [k]);
}
}
Bitmapinfo sbmpinfo;
: Zeromemory (& sbmpinfo, sizeof (bitmapinfo ));
Sbmpinfo. bmiheader. bisize = sizeof (bitmapinfoheader );
Sbmpinfo. bmiheader. biwidth = Cx;
Sbmpinfo. bmiheader. biheight = Cy;
Sbmpinfo. bmiheader. bibitcount = 32;
Sbmpinfo. bmiheader. biplanes = 1;
Sbmpinfo. bmiheader. bicompression = bi_rgb;
Sbmpinfo. bmiheader. bisizeimage = 32 * CX;
Stretchdibits (PDC-> m_hdc, CX, Cy, CX, Cy, Data, & sbmpinfo, dib_rgb_colors, srccopy );
Delete [] data;
Assert_valid (pdoc );
// Todo: Add draw code for native data here
}