﻿ The Fractal Fern
The Fractal Fern
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To draw the Fractal Fern on the PixelBlock, mix in the CFernStencil class below and define the BlendPixel abstract method to use CPixelBlock::BlendPixel:
This class uses Fractal principles to create a picture of a Fern Leaf.
Though far from an optimum way of drawing a leaf it's fascinating for its mystery!
All it's doing is firing pseudo-random pixels with a probability distribution specifying more or less likely areas to effect.
The loop counter can be increased for a denser leaf. Try playing with the other values to see the effects...
```class CFernStencil {
virtual void BlendPixel(WORD x, WORD y, DWORD Colour, BYTE Transparency) =0;
public:
CFernStencil() {}
void Fern(WORD x0=0, WORD y0=0, int Scale=0) {
if(x0==0) x0=GetWidth()/2;
if(y0==0) y0=GetHeight();
if(Scale==0) Scale=y0/10;
double x=0,y=0,t;
long LastRand=1;
for(long g=100*Scale*Scale; g; --g) {
int n=(int)((LastRand=LastRand*214013L+2531011L) & 0x7FFF); // Random number generator.
if(n< 328) {t= 0            ; y=        0.16*y     ;} // 1% Stem
else if(n<2621) {t= 0.2 *x-0.26*y; y= 0.28*x+0.22*y+1.6 ;} // 7% Left Frond
else if(n<4915) {t=-0.15*x+0.28*y; y= 0.26*x+0.24*y+0.44;} // 7% Right Frond
else            {t= 0.85*x+0.04*y; y=-0.04*x+0.85*y+1.6 ;} // 85% Next Position
BlendPixel((WORD)(x0+(x=t)*Scale),(WORD)(y0-y*Scale), 0x00D000, 64);
} }
};
```
You can mix in as many 'Stencils' as you like to provide all the primitives you need.

The Colours, Drawing and Effects sections have further extensions.

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