Updated old Googly Eyes screen saver

'=============== 'GOOGLYEYES4.BAS '=============== 'Blinking Eyes drift around, looking in direction they go. 'Shows how to create images off screen to use with _PUTIMAGE. 'Demo also shows how to move the images in interesting ways. 'Has a scrolling background image. 'Coded by Dav, JULY/2023 'V4 - Clicking eyes make them go googly and run off screen. ' Added a sound effect when clicking on them. ' Added a rotating background image. ' Added press ESC to quit '=== First, create 4 eye images to use.... '=== Create image of eyes looking left eyeleft& = _NEWIMAGE(230, 200, 32) _DEST eyeleft& 'point to above image so we can draw to it ball 50, 50, 50, 255, 255, 255 'left eye ball 30, 50, 20, 0, 0, 128 'left pupil ball 150, 50, 50, 255, 255, 255 'right eye ball 130, 50, 20, 0, 0, 128 'right pupil CIRCLE (50, 50), 50, _RGB(0, 0, 0) CIRCLE (150, 50), 50, _RGB(0, 0, 0) CIRCLE (30, 50), 20, _RGB(0, 0, 0) CIRCLE (130, 50), 20, _RGB(0, 0, 0) '=== Create image of eyes looking right eyeright& = _NEWIMAGE(230, 200, 32) _DEST eyeright& 'point to above image so we can draw to it ball 50, 50, 50, 255, 255, 255 ball 70, 50, 20, 0, 0, 128 ball 150, 50, 50, 255, 255, 255 ball 170, 50, 20, 0, 0, 128 CIRCLE (50, 50), 50, _RGB(0, 0, 0) CIRCLE (150, 50), 50, _RGB(0, 0, 0) CIRCLE (70, 50), 20, _RGB(0, 0, 0) CIRCLE (170, 50), 20, _RGB(0, 0, 0) '=== Create an image of eyes looking up eyeup& = _NEWIMAGE(230, 200, 32) _DEST eyeup& 'point to above image so we can draw to it ball 50, 50, 50, 255, 255, 255 ball 50, 30, 20, 0, 0, 128 ball 150, 50, 50, 255, 255, 255 ball 150, 30, 20, 0, 0, 128 CIRCLE (50, 50), 50, _RGB(0, 0, 0) CIRCLE (150, 50), 50, _RGB(0, 0, 0) CIRCLE (50, 30), 20, _RGB(0, 0, 0) CIRCLE (150, 30), 20, _RGB(0, 0, 0) '=== Create an image of eyes looking down eyedown& = _NEWIMAGE(230, 200, 32) _DEST eyedown& 'point to above image so we can draw to it ball 50, 50, 50, 255, 255, 255 ball 50, 70, 20, 0, 0, 128 ball 150, 50, 50, 255, 255, 255 ball 150, 70, 20, 0, 0, 128 CIRCLE (50, 50), 50, _RGB(0, 0, 0) CIRCLE (150, 50), 50, _RGB(0, 0, 0) CIRCLE (50, 70), 20, _RGB(0, 0, 0) CIRCLE (150, 70), 20, _RGB(0, 0, 0) '=== Create an image of eyes blinking eyeblink& = _NEWIMAGE(200, 800, 32) _DEST eyeblink& 'point to above image so we can draw to it ball 50, 150, 50, 196, 196, 196 ball 150, 150, 50, 196, 196, 196 ball 50, 150, 20, 64, 64, 128 ball 150, 150, 29, 64, 64, 128 CIRCLE (50, 150), 50, _RGB(0, 0, 0) CIRCLE (150, 150), 50, _RGB(0, 0, 0) '=== Create a background image to use back& = _NEWIMAGE(200, 150, 32) _DEST back& FOR x = -1 TO 200 FOR y = -1 TO 150 LINE (x, y)-(x + RND * 10, y + RND * 10), _RGBA(RND * 32, RND * 32, 25 + RND * 200, 25 + RND * 200), BF NEXT NEXT '=== smooth out the background image... _SOURCE back& FOR u = 1 TO 3 'do it 3 times for extra smooth FOR x = 1 TO 199 FOR y = 1 TO 149 p1~& = POINT(x, y) p2~& = POINT(x + 1, y) p3~& = POINT(x, y + 1) p4~& = POINT(x + 1, y + 1) p5~& = POINT(x - 1, y) p6~& = POINT(x, y - 1) p7~& = POINT(x - 1, y - 1) p8~& = POINT(x - 1, y + 1) p9~& = POINT(x + 1, y - 1) IF x + 1 > 200 THEN p2~& = p1~&: p4~& = p1~&: p9~& = p1~& IF x - 1 < 0 THEN p5~& = p1~&: p7~& = p1~&: p8~& = p1~& IF y + 1 > 150 THEN p3~& = p1~&: p4~& = p1~&: p8~& = p1~& IF y - 1 < 0 THEN p6~& = p1~&: p7~& = p1~&: p9~& = p1~& r = _RED32(p1~&) + _RED32(p2~&) + _RED32(p3~&) + _RED32(p4~&) + _RED32(p5~&) + _RED32(p6~&) + _RED32(p7~&) + _RED32(p8~&) + _RED32(p9~&) g = _GREEN32(p1~&) + _GREEN32(p2~&) + _GREEN32(p3~&) + _GREEN32(p4~&) + _GREEN32(p5~&) + _GREEN32(p6~&) + _GREEN32(p7~&) + _GREEN32(p8~&) + _GREEN32(p9~&) b = _BLUE32(p1~&) + _BLUE32(p2~&) + _BLUE32(p3~&) + _BLUE32(p4~&) + _BLUE32(p5~&) + _BLUE32(p6~&) + _BLUE32(p7~&) + _BLUE32(p8~&) + _BLUE32(p9~&) PSET (x, y), _RGB(r / 9, g / 9, b / 9) NEXT NEXT NEXT '=== Now we point to main screen _SOURCE 0 _DEST 0 'set destination to draw to main screen SCREEN _NEWIMAGE(1000, 800, 32) 'main screen size RANDOMIZE TIMER 'do this so the RND call is different everytime Eyes = 50 'the number of eyes on screen EyeSizeMax = 250 'largest size eyes can be DIM EyeX(Eyes), EyeY(Eyes) 'x/y position of the eye DIM EyeSize(Eyes) ' size of eye DIM EyeGrowth(Eyes) 'eye growing or shrinking on screen DIM EyeDrift(Eyes) 'direction eye drifts across screen DIM EyeDriftSpeed(Eyes) 'speed for the drift DIM EyeBlinkFlag(Eyes) 'eyes blinking flag DIM EyeBlinkCount(Eyes) DIM EyeGoogly(Eyes) 'generate eye values FOR d = 1 TO Eyes EyeX(d) = RND * _WIDTH 'make random x position EyeY(d) = RND * _HEIGHT 'make random y position EyeSize(d) = (RND * EyeSizeMax) 'random eye size, up to EyeSizeMax EyeGrowth(d) = INT(RND * 2) 'make way eye size is changing, 0=shrinking, 1=growing EyeDrift(d) = INT(RND * 4) 'make random direction a eye can drift (4 different ways) EyeDriftSpeed(d) = INT(RND * 3) + 2 'speed eyes will be drifting EyeBlinkFlag(d) = 0 'if eye is blinking or not EyeBlinkCount(d) = 0 EyeGoogly(d) = 0 NEXT DO WHILE _MOUSEINPUT: WEND 'Bubble sort through eyesize, putting smallest size first so.. '..they will be _PUTIMAGE'd first, putting them in the background. FOR b = 1 TO Eyes FOR b2 = 1 TO Eyes IF EyeSize(b2) > EyeSize(b) THEN SWAP EyeX(b), EyeX(b2) SWAP EyeY(b), EyeY(b2) SWAP EyeSize(b), EyeSize(b2) SWAP EyeGrowth(b), EyeGrowth(b2) SWAP EyeDrift(b), EyeDrift(b2) SWAP EyeDriftSpeed(b), EyeDriftSpeed(b2) SWAP EyeBlinkFlag(b), EyeBlinkFlag(b2) SWAP EyeBlinkCount(b), EyeBlinkCount(b2) END IF NEXT NEXT 'CLS 'I don't think CLS is needed now, the back& image clears screen '=== rotozoom background image RotoZoom3 _WIDTH / 2, _HEIGHT / 2, back&, 30, 8, a a = a + .01: IF a >= 360 THEN a = a - 360 '=== step through each eye FOR d = 1 TO Eyes 'if eye is shrinking, subtract eyesize, else add to it IF EyeGrowth(d) = 0 THEN EyeSize(d) = EyeSize(d) - 1 ELSE EyeSize(d) = EyeSize(d) + 1 END IF 'if eyesize reaches max size, switch growth to 0 start shrinking instead IF EyeSize(d) >= EyeSizeMax THEN EyeGrowth(d) = 0 'if if reaches smallest eyesize, switch growth to 1 to start growing now IF EyeSize(d) <= 20 THEN EyeGrowth(d) = 1 'drift eye in 1 of 4 directions we generated, and do +x,-x,+y,-y to it. IF EyeDrift(d) = 0 THEN EyeX(d) = EyeX(d) + EyeDriftSpeed(d) 'drift right IF EyeDrift(d) = 1 THEN EyeX(d) = EyeX(d) - EyeDriftSpeed(d) 'drift left IF EyeDrift(d) = 2 THEN EyeY(d) = EyeY(d) + EyeDriftSpeed(d) 'drift down IF EyeDrift(d) = 3 THEN EyeY(d) = EyeY(d) - EyeDriftSpeed(d) 'drift up 'this creates the shakiness. randomly adjust x/y positions by +/-2 each step IF INT(RND * 2) = 0 THEN EyeX(d) = EyeX(d) + 2 ELSE EyeX(d) = EyeX(d) - 2 IF INT(RND * 2) = 0 THEN EyeY(d) = EyeY(d) + 2 ELSE EyeY(d) = EyeY(d) - 2 'below handles if eye goes off screen, let it dissapear completely. 'If it had been clicked and Gone Googly, then reset speed afterwards IF EyeX(d) > _WIDTH + EyeSize(d) THEN EyeX(d) = -EyeSize(d): EyeDriftSpeed(d) = INT(RND * 3) + 2 IF EyeX(d) < -EyeSize(d) THEN EyeX(d) = _WIDTH + EyeSize(d): EyeDriftSpeed(d) = INT(RND * 3) + 2 IF EyeY(d) > _HEIGHT + EyeSize(d) THEN EyeY(d) = -EyeSize(d): EyeDriftSpeed(d) = INT(RND * 3) + 2 IF EyeY(d) < -EyeSize(d) THEN EyeY(d) = _HEIGHT + EyeSize(d): EyeDriftSpeed(d) = INT(RND * 3) + 2 'drift eye in 1 of 4 directions we generated, and +x,-x,+y,-y to it. 'If blinking flag on... IF EyeBlinkFlag(d) = 1 THEN SELECT CASE EyeBlinkCount(d) CASE 0 TO 3 _PUTIMAGE (EyeX(d), EyeY(d))-(EyeX(d) + EyeSize(d), EyeY(d) + EyeSize(d)), eyeblink& CASE 4 TO 8 LINE (EyeX(d), EyeY(d) + (EyeSize(d) / 6))-(EyeX(d) + EyeSize(d), EyeY(d) + (EyeSize(d) / 6) + 3), _RGB(64, 64, 64), BF CASE 9 TO 12 _PUTIMAGE (EyeX(d), EyeY(d))-(EyeX(d) + EyeSize(d), EyeY(d) + EyeSize(d)), eyeblink& END SELECT EyeBlinkCount(d) = EyeBlinkCount(d) + 1 IF EyeBlinkCount(d) > 12 THEN EyeBlinkCount(d) = 0 EyeBlinkFlag(d) = 0 END IF ELSE 'showing normal eyes IF EyeDrift(d) = 0 THEN _PUTIMAGE (EyeX(d), EyeY(d))-(EyeX(d) + EyeSize(d), EyeY(d) + EyeSize(d)), eyeright& 'drift right IF EyeDrift(d) = 1 THEN _PUTIMAGE (EyeX(d), EyeY(d))-(EyeX(d) + EyeSize(d), EyeY(d) + EyeSize(d)), eyeleft& 'drift left IF EyeDrift(d) = 2 THEN _PUTIMAGE (EyeX(d), EyeY(d))-(EyeX(d) + EyeSize(d), EyeY(d) + EyeSize(d)), eyedown& 'drift down IF EyeDrift(d) = 3 THEN _PUTIMAGE (EyeX(d), EyeY(d))-(EyeX(d) + EyeSize(d), EyeY(d) + EyeSize(d)), eyeup& 'drift up END IF 'Add code here to add nose and mouth to the here (next version...) 'get random direction change,growth and blinking once in a while SELECT CASE INT(RND * 300) CASE 1: EyeDrift(d) = 0: EyeDriftSpeed(d) = INT(RND * 3) + 2 CASE 2: EyeDrift(d) = 1: EyeDriftSpeed(d) = INT(RND * 3) + 2 CASE 3: EyeDrift(d) = 2: EyeDriftSpeed(d) = INT(RND * 3) + 2 CASE 4: EyeDrift(d) = 3: EyeDriftSpeed(d) = INT(RND * 3) + 2 CASE 5: EyeGrowth(d) = 0 CASE 6: EyeGrowth(d) = 1 CASE 7: IF EyeBlinkFlag(d) = 0 THEN EyeBlinkFlag(d) = 1 END SELECT IF _MOUSEBUTTON(1) THEN mx = _MOUSEX: my = _MOUSEY IF mx > EyeX(d) AND mx < EyeX(d) + EyeSize(d) AND my > EyeY(d) AND my < EyeY(d) + EyeSize(d) THEN EyeGrowth(d) = INT(RND * 2) EyeDrift(d) = INT(RND * 4) EyeDriftSpeed(d) = EyeDriftSpeed(d) + 4 SOUND 7000 + (RND * 3000), .1 END IF END IF NEXT _DISPLAY _LIMIT 30 LOOP UNTIL INKEY$ = CHR$(27) SYSTEM SUB ball (x, y, size, r&, g&, b&) 'small sub that draws a filled ball with given color. FOR s = 1 TO size STEP .4 CIRCLE (x, y), s, _RGB(r&, g&, b&) r& = r& - 1: g& = g& - 1: b& = b& - 1 NEXT END SUB SUB RotoZoom3 (X AS LONG, Y AS LONG, Image AS LONG, xScale AS SINGLE, yScale AS SINGLE, radianRotation AS SINGLE) DIM px(3) AS SINGLE: DIM py(3) AS SINGLE ' simple arrays for x, y to hold the 4 corners of image DIM W&, H&, sinr!, cosr!, i&, x2&, y2& ' variables for image manipulation W& = _WIDTH(Image&): H& = _HEIGHT(Image&) px(0) = -W& / 2: py(0) = -H& / 2 'left top corner px(1) = -W& / 2: py(1) = H& / 2 ' left bottom corner px(2) = W& / 2: py(2) = H& / 2 ' right bottom px(3) = W& / 2: py(3) = -H& / 2 ' right top sinr! = SIN(-radianRotation): cosr! = COS(-radianRotation) ' rotation helpers FOR i& = 0 TO 3 ' calc new point locations with rotation and zoom x2& = xScale * (px(i&) * cosr! + sinr! * py(i&)) + X: y2& = yScale * (py(i&) * cosr! - px(i&) * sinr!) + Y px(i&) = x2&: py(i&) = y2& NEXT _MAPTRIANGLE _SEAMLESS(0, 0)-(0, H& - 1)-(W& - 1, H& - 1), Image TO(px(0), py(0))-(px(1), py(1))-(px(2), py(2)) _MAPTRIANGLE _SEAMLESS(0, 0)-(W& - 1, 0)-(W& - 1, H& - 1), Image TO(px(0), py(0))-(px(3), py(3))-(px(2), py(2)) END SUB

Code: (Select All)

_Title "All Eyes on the Bee"

' B+ 2019-03-06

' 2020-05-13 add smile

' 2023-07-09 multiply and avoid!



Const smile = 1 / 3 * _Pi

Screen _NewImage(1280, 720, 12)

_FullScreen

Dim Shared mx, my, maxDist

maxDist = _Hypot(_Width / 2, _Height / 2)

nFaces = 40

Dim Shared fx(1 To nFaces), fy(1 To nFaces), fdx(1 To nFaces), fdy(1 To nFaces)

Dim Shared fsz(1 To nFaces), fc(1 To nFaces)

For i = 1 To nFaces

    fx(i) = Rnd * _Width: fy(i) = Rnd * _Height

    fdx(i) = Rnd * 6 - 3: fdy(i) = Rnd * 6 - 3

    fsz(i) = Rnd * 60 + 20: fc(i) = Int(Rnd * 15)

Next



Color , 15

_MouseHide

While _KeyDown(27) = 0 'until esc keypress

    Cls

    For i = 1 To nFaces

        fx(i) = fx(i) + fdx(i)

        fy(i) = fy(i) + fdy(i)

        If fx(i) < 0 Then fx(i) = fx(i) + _Width

        If fx(i) > _Width Then fx(i) = fx(i) - _Width

        If fy(i) < 0 Then fy(i) = fy(i) + _Height

        If fy(i) > _Height Then fy(i) = fy(i) - _Height



        drawFace i

    Next

    While _MouseInput: Wend

    mx = _MouseX: my = _MouseY

    ' bee body

    For i = 1 To 8

        If i Mod 2 Then bc = 0 Else bc = 14

        FillCircle mx + i * 3, my + i * 3, 5, bc

    Next

    ' bee wings

    FillCircle mx - 15 + 20, my + 10, 8, 7

    FillCircle mx + 8 + 20, my + 5, 8, 7

    _Display 'prevent flicker

    _Limit 30 'save CPU fan

Wend



Sub drawFace (i)

    If _Hypot(fx(i) - mx, fy(i) - my) < 100 Then

        avoid = _Atan2(fy(i) - my, fx(i) - mx)

        speed = 103 - _Hypot(fx(i) - mx, fy(i) - my)

        fdx(i) = speed * Cos(avoid)

        fdy(i) = speed * Sin(avoid)

    End If



    angle = _Atan2(my - fy(i), mx - (fx(i) - .45 * fsz(i)))

    angle2 = _Atan2(my - fy(i), mx - (fx(i) + .45 * fsz(i)))

    FillCircle fx(i), fy(i), fsz(i), fc(i)



    FEllipse fx(i) - .45 * fsz(i), fy(i), .35 * fsz(i), .25 * fsz(i), 15

    FEllipse fx(i) + .45 * fsz(i), fy(i), .35 * fsz(i), .25 * fsz(i), 15

    x1 = fx(i) - .45 * fsz(i) + .125 * fsz(i) * Cos(angle)

    y1 = fy(i) + .10 * fsz(i) * Sin(angle)

    x2 = fx(i) + .45 * fsz(i) + .125 * fsz(i) * Cos(angle2)

    y2 = fy(i) + .10 * fsz(i) * Sin(angle2)

    FillCircle x1, y1, .17 * fsz(i), 9

    FillCircle x2, y2, .17 * fsz(i), 9

    FillCircle x1, y1, .09 * fsz(i), 0

    FillCircle x2, y2, .09 * fsz(i), 0



    mw = _Hypot(mx - fx(i), my - fy(i)) * 100 / _Hypot(_Width, _Height) + 2

    arc fx(i), fy(i), .73 * fsz(i), _Pi / 2 - smile * mw / 100, _Pi / 2 + smile * mw / 100, 15

End Sub



'fill circle

Sub FillCircle (CX As Integer, CY As Integer, R As Integer, C As _Unsigned Long)

    Dim Radius As Integer, RadiusError As Integer

    Dim X As Integer, Y As Integer



    Radius = Abs(R)

    RadiusError = -Radius

    X = Radius

    Y = 0



    If Radius = 0 Then PSet (CX, CY), C: Exit Sub



    ' Draw the middle span here so we don't draw it twice in the main loop,

    ' which would be a problem with blending turned on.

    Line (CX - X, CY)-(CX + X, CY), C, BF



    While X > Y

        RadiusError = RadiusError + Y * 2 + 1

        If RadiusError >= 0 Then

            If X <> Y + 1 Then

                Line (CX - Y, CY - X)-(CX + Y, CY - X), C, BF

                Line (CX - Y, CY + X)-(CX + Y, CY + X), C, BF

            End If

            X = X - 1

            RadiusError = RadiusError - X * 2

        End If

        Y = Y + 1

        Line (CX - X, CY - Y)-(CX + X, CY - Y), C, BF

        Line (CX - X, CY + Y)-(CX + X, CY + Y), C, BF

    Wend

End Sub



'use radians

Sub arc (x, y, r, raStart, raStop, c As _Unsigned Long)

    Dim al, a

    'x, y origin, r = radius, c = color



    'raStart is first angle clockwise from due East = 0 degrees

    ' arc will start drawing there and clockwise until raStop angle reached



    If raStop < raStart Then

        arc x, y, r, raStart, _Pi(2), c

        arc x, y, r, 0, raStop, c

    Else

        ' modified to easier way suggested by Steve

        'Why was the line method not good? I forgot.

        al = _Pi * r * r * (raStop - raStart) / _Pi(2)

        For a = raStart To raStop Step 1 / al

            Circle (x + r * Cos(a), y + r * Sin(a)), 1, c '<<< modify for smile

        Next

    End If

End Sub



Sub FEllipse (CX As Long, CY As Long, xr As Long, yr As Long, C As _Unsigned Long)

    If xr = 0 Or yr = 0 Then Exit Sub

    Dim h2 As _Integer64, w2 As _Integer64, h2w2 As _Integer64

    Dim x As Long, y As Long

    w2 = xr * xr: h2 = yr * yr: h2w2 = h2 * w2

    Line (CX - xr, CY)-(CX + xr, CY), C, BF

    Do While y < yr

        y = y + 1

        x = Sqr((h2w2 - y * y * w2) \ h2)

        Line (CX - x, CY + y)-(CX + x, CY + y), C, BF

        Line (CX - x, CY - y)-(CX + x, CY - y), C, BF

    Loop

End Sub

Code: (Select All)

$resize:on



deflng a-z



sw = 640

sh = 600



screen _newimage(sw,sh,32),,1,0



line (0,0)-(sw,sh),_rgb(255,255,255),bf



ellipsef sw/4, sh/2, 0.9*sw/4, 0.9*sh/2, _rgb(0,0,0)

ellipsef 3*sw/4, sh/2, 0.9*sw/4, 0.9*sh/2, _rgb(0,0,0)



ellipsef sw/4, sh/2, 0.8*sw/4, 0.8*sh/2, _rgb(255,255,255)

ellipsef 3*sw/4, sh/2, 0.8*sw/4, 0.8*sh/2, _rgb(255,255,255)



screen ,,0,0



dim a as double, b as double

do

    do

        mx = _mousex

        my = _mousey

    loop while _mouseinput



    if _resize then

        sw = _resizewidth

        sh = _resizeheight



        screen ,,1,0

        line (0,0)-(sw,sh),_rgb(255,255,255),bf



        ellipsef sw/4, sh/2, 0.9*sw/4, 0.9*sh/2, _rgb(0,0,0)

        ellipsef 3*sw/4, sh/2, 0.9*sw/4, 0.9*sh/2, _rgb(0,0,0)



        ellipsef sw/4, sh/2, 0.8*sw/4, 0.8*sh/2, _rgb(255,255,255)

        ellipsef 3*sw/4, sh/2, 0.8*sw/4, 0.8*sh/2, _rgb(255,255,255)

        screen ,,0,0

    end if



    pcopy 1,0



    a = _atan2(sh/2 - my, sw/4 - mx)

    b = _atan2(sh/2 - my, 3*sw/4 - mx)



    x1 = sw/4 - 0.5*sw*cos(a)/4

    y1 = sh/2 - 0.5*sh*sin(a)/2

    if abs(sw/4-mx) < 0.5*sw/4 or abs(sh/2-my) < 0.5*sh/2 then

        x1 = mx

        y1 = my

    end if



    x2 = 3*sw/4 - 0.5*sw*cos(b)/4

    y2 = sh/2 - 0.5*sh*sin(b)/2

    if abs(3*sw/4-mx) < 0.5*sw/4 or abs(sh/2-my) < 0.5*sh/2 then

        x2 = mx

        y2 = my

    end if



    ellipsef x1, y1, 0.2*sw/4, 0.2*sh/2, _rgb(0,0,0)

    ellipsef x2, y2, 0.2*sw/4, 0.2*sh/2, _rgb(0,0,0)



    _display

loop until _keyhit = 27

system



sub ellipsef (x0, y0, rx, ry, c)

    a = 2*rx*rx

    b = 2*ry*ry



    x = rx

    y = 0

    xx = ry*ry*(1 - 2*rx)

    yy = rx*rx



    e = 0

    sx = b*rx

    sy = 0



    do while sx >= sy

        line (x0 - x, y0 + y)-(x0 + x, y0 + y), c, bf

        line (x0 - x, y0 - y)-(x0 + x, y0 - y), c, bf



        y = y + 1

        sy = sy + a

        e = e + yy

        yy = yy + a



        if 2*e + xx > 0 then

            x = x - 1

            sx = sx - b

            e = e + xx

            xx = xx + b

        end if

    loop



    x = 0

    y = ry

    xx = rx*ry

    yy = rx*rx*(1 - 2*ry)



    e = 0

    sx = 0

    sy = a*ry



    do while sx <= sy

        line (x0 - x, y0 - y)-(x0 + x, y0 - y), c, bf

        line (x0 - x, y0 + y)-(x0 + x, y0 + y), c, bf



        x = x + 1

        sx = sx + b

        e = e + xx

        xx = xx + b



        if 2*e + yy > 0 then

            y = y - 1

            sy = sy - a

            e = e + yy

            yy = yy + a

        end if

    loop

end sub