Curve Smoother by STxAxTIC & FellippeHeitor

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The Librarian:
Curve Smoother

Author: @STxAxTIC @FellippeHeitor
Source: Submission
Version: 2014
Tags: [graphics], [relaxation algorithm], [anti-aliasing]

Description:
This program demonstrates (i) linear interpolation to create a curve between points, (ii) a relaxation algorithm to "smooth over" a curve to remove sharp edges, and (iii) plotting with anti-aliasing.

Source code:

--- Code: QB64: ---' DisplaySCREEN _NEWIMAGE(800, 600, 32)_SCREENMOVE (_DESKTOPWIDTH \ 2 - _WIDTH \ 2) - 3, (_DESKTOPHEIGHT \ 2 - _HEIGHT \ 2) - 29_TITLE "If these curves were smoother they'd steal your wife."_DELAY 1 ' Metastart:CLEARCLSRANDOMIZE TIMER ' Data structuresTYPE Vector x AS DOUBLE y AS DOUBLEEND TYPE ' Object typeTYPE Object Elements AS INTEGER Shade AS _UNSIGNED LONGEND TYPE ' Object storageDIM SHARED Shape(300) AS ObjectDIM SHARED PointChain(300, 500) AS VectorDIM SHARED TempChain(300, 500) AS VectorDIM SHARED ShapeCount AS INTEGERDIM SHARED SelectedShape AS INTEGER ' InitializeShapeCount = 0 ' Main loopDO IF (UserInput = -1) THEN GOTO start CALL Graphics _LIMIT 120LOOP END FUNCTION UserInput TheReturn = 0 ' Keyboard input kk = _KEYHIT SELECT CASE kk CASE 32 DO: LOOP UNTIL _KEYHIT WHILE _MOUSEINPUT: WEND _KEYCLEAR CALL NewMouseShape(7.5, 150, 15) CLS END SELECT IF (kk) THEN _KEYCLEAR END IF UserInput = TheReturnEND FUNCTION SUB Graphics LINE (0, 0)-(_WIDTH, _HEIGHT), _RGBA(0, 0, 0, 200), BF CALL cprintstring(16 * 17, "PRESS SPACE and then drag MOUSE 1 to draw a new shape.") FOR ShapeIndex = 1 TO ShapeCount FOR i = 1 TO Shape(ShapeIndex).Elements - 1 CALL lineSmooth(PointChain(ShapeIndex, i).x, PointChain(ShapeIndex, i).y, PointChain(ShapeIndex, i + 1).x, PointChain(ShapeIndex, i + 1).y, Shape(ShapeIndex).Shade) NEXT NEXT _DISPLAYEND SUB SUB NewMouseShape (rawresolution AS DOUBLE, targetpoints AS INTEGER, smoothiterations AS INTEGER) ShapeCount = ShapeCount + 1 numpoints = 0 xold = 999 ^ 999 yold = 999 ^ 999 DO DO WHILE _MOUSEINPUT x = _MOUSEX y = _MOUSEY IF (x > 0) AND (x < _WIDTH) AND (y > 0) AND (y < _HEIGHT) THEN IF _MOUSEBUTTON(1) THEN x = x - (_WIDTH / 2) y = -y + (_HEIGHT / 2) delta = SQR((x - xold) ^ 2 + (y - yold) ^ 2) IF (delta > rawresolution) AND (numpoints < targetpoints - 1) THEN numpoints = numpoints + 1 PointChain(ShapeCount, numpoints).x = x PointChain(ShapeCount, numpoints).y = y CALL cpset(x, y, _RGB(0, 255, 255)) xold = x yold = y END IF END IF END IF LOOP _DISPLAY LOOP UNTIL NOT _MOUSEBUTTON(1) AND (numpoints > 1) DO WHILE (numpoints < targetpoints) rad2max = -1 kmax = -1 FOR k = 1 TO numpoints - 1 xfac = PointChain(ShapeCount, k).x - PointChain(ShapeCount, k + 1).x yfac = PointChain(ShapeCount, k).y - PointChain(ShapeCount, k + 1).y rad2 = xfac ^ 2 + yfac ^ 2 IF rad2 > rad2max THEN kmax = k rad2max = rad2 END IF NEXT FOR j = numpoints TO kmax + 1 STEP -1 PointChain(ShapeCount, j + 1).x = PointChain(ShapeCount, j).x PointChain(ShapeCount, j + 1).y = PointChain(ShapeCount, j).y NEXT PointChain(ShapeCount, kmax + 1).x = (1 / 2) * (PointChain(ShapeCount, kmax).x + PointChain(ShapeCount, kmax + 2).x) PointChain(ShapeCount, kmax + 1).y = (1 / 2) * (PointChain(ShapeCount, kmax).y + PointChain(ShapeCount, kmax + 2).y) numpoints = numpoints + 1 LOOP FOR j = 1 TO smoothiterations FOR k = 2 TO numpoints - 1 TempChain(ShapeCount, k).x = (1 / 2) * (PointChain(ShapeCount, k - 1).x + PointChain(ShapeCount, k + 1).x) TempChain(ShapeCount, k).y = (1 / 2) * (PointChain(ShapeCount, k - 1).y + PointChain(ShapeCount, k + 1).y) NEXT FOR k = 2 TO numpoints - 1 PointChain(ShapeCount, k).x = TempChain(ShapeCount, k).x PointChain(ShapeCount, k).y = TempChain(ShapeCount, k).y NEXT NEXT Shape(ShapeCount).Elements = numpoints Shape(ShapeCount).Shade = _RGB(100 + INT(RND * 155), 100 + INT(RND * 155), 100 + INT(RND * 155)) SelectedShape = ShapeCountEND SUB SUB cpset (x1, y1, col AS _UNSIGNED LONG) PSET (_WIDTH / 2 + x1, -y1 + _HEIGHT / 2), colEND SUB SUB cprintstring (y, a AS STRING) _PRINTSTRING (_WIDTH / 2 - (LEN(a) * 8) / 2, -y + _HEIGHT / 2), aEND SUB SUB lineSmooth (x0, y0, x1, y1, c AS _UNSIGNED LONG) 'translated from 'https://en.wikipedia.org/w/index.php?title=Xiaolin_Wu%27s_line_algorithm&oldid=852445548 DIM plX AS INTEGER, plY AS INTEGER, plI DIM steep AS _BYTE steep = ABS(y1 - y0) > ABS(x1 - x0) IF steep THEN SWAP x0, y0 SWAP x1, y1 END IF IF x0 > x1 THEN SWAP x0, x1 SWAP y0, y1 END IF DIM dx, dy, gradient dx = x1 - x0 dy = y1 - y0 gradient = dy / dx IF dx = 0 THEN gradient = 1 END IF 'handle first endpoint DIM xend, yend, xgap, xpxl1, ypxl1 xend = _ROUND(x0) yend = y0 + gradient * (xend - x0) xgap = (1 - ((x0 + .5) - INT(x0 + .5))) xpxl1 = xend 'this will be used in the main loop ypxl1 = INT(yend) IF steep THEN plX = ypxl1 plY = xpxl1 plI = (1 - (yend - INT(yend))) * xgap GOSUB plot plX = ypxl1 + 1 plY = xpxl1 plI = (yend - INT(yend)) * xgap GOSUB plot ELSE plX = xpxl1 plY = ypxl1 plI = (1 - (yend - INT(yend))) * xgap GOSUB plot plX = xpxl1 plY = ypxl1 + 1 plI = (yend - INT(yend)) * xgap GOSUB plot END IF DIM intery intery = yend + gradient 'first y-intersection for the main loop 'handle second endpoint DIM xpxl2, ypxl2 xend = _ROUND(x1) yend = y1 + gradient * (xend - x1) xgap = ((x1 + .5) - INT(x1 + .5)) xpxl2 = xend 'this will be used in the main loop ypxl2 = INT(yend) IF steep THEN plX = ypxl2 plY = xpxl2 plI = (1 - (yend - INT(yend))) * xgap GOSUB plot plX = ypxl2 + 1 plY = xpxl2 plI = (yend - INT(yend)) * xgap GOSUB plot ELSE plX = xpxl2 plY = ypxl2 plI = (1 - (yend - INT(yend))) * xgap GOSUB plot plX = xpxl2 plY = ypxl2 + 1 plI = (yend - INT(yend)) * xgap GOSUB plot END IF 'main loop DIM x IF steep THEN FOR x = xpxl1 + 1 TO xpxl2 - 1 plX = INT(intery) plY = x plI = (1 - (intery - INT(intery))) GOSUB plot plX = INT(intery) + 1 plY = x plI = (intery - INT(intery)) GOSUB plot intery = intery + gradient NEXT ELSE FOR x = xpxl1 + 1 TO xpxl2 - 1 plX = x plY = INT(intery) plI = (1 - (intery - INT(intery))) GOSUB plot plX = x plY = INT(intery) + 1 plI = (intery - INT(intery)) GOSUB plot intery = intery + gradient NEXT END IF EXIT SUB plot: ' Change to regular PSET for standard coordinate orientation. CALL cpset(plX, plY, _RGB32(_RED32(c), _GREEN32(c), _BLUE32(c), plI * 255)) RETURNEND SUB

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