Skia Fiddle

Options

Width Height

check_box_outline_blank check_box Text Only [Use SkDebugf()]

check_box_outline_blank check_box sRGB

check_box_outline_blank check_box F16

check_box_outline_blank check_box Animation

Duration (seconds)

These globals are now defined:

double duration; // The requested duration of the animation.
double frame;    // A value in [0, 1] of where we are in the animation.

check_box_outline_blank check_box Offscreen Render Target

Width Height Sample Count

check_box_outline_blank check_box Texturable

check_box_outline_blank check_box MipMap

This global is now defined:

GrBackendRenderTarget backEndRenderTarget;

GrBackendTexture backEndTextureRenderTarget;

Optional source image

check_box_outline_blank check_box MipMap

These globals are now defined:

SkBitmap source;
sk_sp<SkImage> image;
GrBackendTexture backEndTexture; // GPU Only.

Note:

Adding comments with SK_FOLD_START and SK_FOLD_END creates foldable code blocks.
These blocks will be folded by default and are useful for highlighting specific lines of code.
You can also use the keyboard shortcuts Ctrl+S and Ctrl+E in the code editor to set them.

xxxxxxxxxx
 
// L-System
// https://en.wikipedia.org/wiki/L-system#Example_7:_Fractal_plant
​
struct rules_t {
    char c;
    std::string s;
};
​
rules_t rules[6] = {
    {'X', "F-[[X]+X]+F[+FX]-X"},
    {'F', "FF"},
    {'+', "+"},
    {'-', "-"},
    {'[', "["},
    {']', "]"},
};
​
std::string E(std::string s) {
    if (s.size() == 0) {
        return "";
    }
    for (int i=0; i<6; i++) {
        if (rules[i].c == s[0]) {
            return rules[i].s + E(s.substr(1));
        }
    }
    return "";
}
​
struct Pt {
  SkScalar x;
  SkScalar y;
  SkScalar a;
};
​
void draw(SkCanvas* canvas) {
  canvas->drawColor(SK_ColorLTGRAY);
​
  SkPaint p;
  p.setColor(0xFFA6761D);
  p.setAntiAlias(true);
  p.setStyle(SkPaint::kStroke_Style);
  p.setStrokeWidth(1);
​
  std::vector<struct Pt> ptstack;
  std::string plant = E(E(E(E(E("X")))));
  const double len = 2.5;
  struct Pt pt = {128, 256, 3.14};
  SkPath path;
  path.moveTo(pt.x, pt.y);
​
  for (std::string::iterator it=plant.begin(); it!=plant.end(); ++it) {
    if (*it == 'F') {
      pt.x += len*sin(pt.a);
      pt.y += len*cos(pt.a);
      path.lineTo(pt.x, pt.y);
    } else if (*it == '+') {
      pt.a += (0.15 + sin(frame*2.0*3.14159)*0.05);
    } else if (*it == '-') {
      pt.a += (-0.15 + sin(frame*2.0*3.14159)*0.05);
    } else if (*it == '[') {
      ptstack.push_back(pt);
    } else if (*it == ']') {
      pt = ptstack.back();
      ptstack.pop_back();
      path.moveTo(pt.x, pt.y);
    }
  }
  canvas->drawPath(path, p);
}