PSET - mkilgore/QB64pe GitHub Wiki

 '' ''
SCREEN 12
PSET(100, 100), 12
DRAW "U20 R20 D20 L20" '' ''

DIM dmag AS INTEGER, dlogmag AS INTEGER
DIM a AS DOUBLE, b AS DOUBLE, mag AS DOUBLE
DIM dx AS INTEGER, dy AS INTEGER
DIM mx AS INTEGER, my AS INTEGER, mz AS INTEGER

dmag = 16
mag = 1

a = -.75
b = 0
DO
  DIM limitx AS DOUBLE, limit AS INTEGER
  DIM inc AS DOUBLE, left AS DOUBLE, top AS DOUBLE

  limitx = 150 * (LOG(mag) + 1)
  IF...THEN limitx > 32767 THEN limitx = 32767
  limit = INT(limitx)
  inc = .004 / mag
  left = a - inc * 319
  top = b + inc * 239
  CLS

  DIM yy AS INTEGER, xx AS INTEGER
  DIM x AS DOUBLE, y AS DOUBLE, z AS INTEGER

  FOR...NEXT yy = 0 TO 479
    y = top - inc * yy
    FOR...NEXT xx = 0 TO 639
        x = left + inc * xx
        z = mandel(x, y, limit)
        IF...THEN z < limit THEN PSET (xx, yy), 1 + z MOD 15
        IF...THEN INKEY$ = CHR$(27) THEN SYSTEM
    NEXT
  NEXT
  mz = 0
  CALL readmouse(mx, my, mz)
  DO
    dx = 319 \ dmag
    dy = 239 \ dmag
    CALL readmouse(mx, my, mz)
    IF...THEN mz THEN EXIT DO
    CALL rectangle(mx - dx, my - dy, mx + dx, my + dy)
    DIM t AS DOUBLE
    t = TIMER
    WHILE t = TIMER
      key$ = INKEY$
      SELECT CASE key$
        CASE CHR$(27)
          SYSTEM
        CASE CHR$(0) + CHR$(72)
          dmag = dmag \ 2
          IF...THEN dmag < 2 THEN dmag = 2
        CASE CHR$(0) + CHR$(80)
          dmag = dmag * 2
          IF...THEN dmag > 128 THEN dmag = 128
      END SELECT
    WEND
    CALL rectangle(mx - dx, my - dy, mx + dx, my + dy)
  LOOP
  a = a + inc * (mx - 319): b = b - inc * (my - 239)
  IF...THEN (mz = 1) THEN mag = dmag * mag ELSE mag = mag / dmag
  IF...THEN (mag < 1) THEN mag = 1
LOOP

FUNCTION mandel% (x AS DOUBLE, y AS DOUBLE, limit AS INTEGER)
  DIM a AS DOUBLE, b AS DOUBLE, t AS DOUBLE
  DIM n AS INTEGER
  n = 0: a = 0: b = 0
  DO
    t = a * a - b * b + x
    b = 2 * a * b + y: a = t
    n = n + 1
  LOOP UNTIL a * a + b * b > 4 OR (boolean) n > limit
  mandel = n
END FUNCTION

SUB readmouse (x AS INTEGER, y AS INTEGER, z AS INTEGER)
z=0
DO
if _MOUSEBUTTON(1) THEN z = z OR (boolean) 1
if _MOUSEBUTTON(2) THEN z = z OR (boolean) 2
if _MOUSEBUTTON(3) THEN z = z OR (boolean) 4
LOOP UNTIL _MOUSEINPUT=0
x=_MOUSEX
y=_MOUSEY
END SUB

SUB rectangle (x1 AS INTEGER, y1 AS INTEGER, x2 AS INTEGER, y2 AS INTEGER)
  DIM i AS INTEGER, j AS INTEGER
  FOR...NEXT i = x1 TO x2
    j = POINT(i, y1)
    PSET (i, y1), j XOR (boolean) 15
    j = POINT(i, y2)
    PSET (i, y2), j XOR (boolean) 15
  NEXT
  FOR...NEXT i = y1 TO y2
    j = POINT(x1, i)
    PSET (x1, i), j XOR (boolean) 15
    j = POINT(x2, i)
    PSET (x2, i), j XOR (boolean) 15
  NEXT
END SUB