@thi.ng/text-canvas/circle.js

Text based canvas, drawing, plotting, tables with arbitrary formatting (incl. ANSI/HTML)

import { peek } from "@thi.ng/arrays/peek";
import { hline } from "./hvline.js";
import { charCode, intersectRectCircle } from "./utils.js";
const circle = (canvas, cx, cy, r, char, fill = false, format = canvas.format) => {
  if (r < 1) return;
  cx |= 0;
  cy |= 0;
  r |= 0;
  const { x1, y1, x2, y2, w: clipw, h: cliph } = peek(canvas.clipRects);
  if (!intersectRectCircle(x1, y1, clipw, cliph, cx, cy, r)) return;
  char = charCode(
    char !== void 0 ? char : peek(canvas.styles).dot,
    format
  );
  let x = 0;
  let y = r;
  let ymax = r * r;
  let sum = ymax + r;
  let dx2 = 1;
  let dy2 = 2 * r - 1;
  const { data, width } = canvas;
  const $ = (ox, oy) => ox >= x1 && oy >= y1 && ox < x2 && oy < y2 && (data[ox + oy * width] = char);
  while (x <= y) {
    if (fill) {
      hline(canvas, cx - y, cy + x, y << 1, char, char, char);
      x && hline(canvas, cx - y, cy - x, y << 1, char, char, char);
    } else {
      $(cx - y, cy + x);
      y && $(cx + y, cy + x);
      if (x) {
        $(cx - y, cy - x);
        y && $(cx + y, cy - x);
      }
      if (x !== y) {
        $(cx - x, cy - y);
        x && $(cx + x, cy - y);
        if (y) {
          $(cx - x, cy + y);
          x && $(cx + x, cy + y);
        }
      }
    }
    sum -= dx2;
    if (sum <= ymax) {
      if (fill && x !== y) {
        hline(canvas, cx - x, cy - y, x << 1, char, char, char);
        y && hline(canvas, cx - x, cy + y, x << 1, char, char, char);
      }
      y--;
      ymax -= dy2;
      dy2 -= 2;
    }
    x++;
    dx2 += 2;
  }
};
export {
  circle
};