arc-2-cubic.js 5.0 KB

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  1. var TAU = Math.PI * 2;
  2. var mapToEllipse = function (_a, rx, ry, cosphi, sinphi, centerx, centery) {
  3. var x = _a.x, y = _a.y;
  4. x *= rx;
  5. y *= ry;
  6. var xp = cosphi * x - sinphi * y;
  7. var yp = sinphi * x + cosphi * y;
  8. return {
  9. x: xp + centerx,
  10. y: yp + centery
  11. };
  12. };
  13. var approxUnitArc = function (ang1, ang2) {
  14. // If 90 degree circular arc, use a constant
  15. // as derived from http://spencermortensen.com/articles/bezier-circle
  16. var a = ang2 === 1.5707963267948966
  17. ? 0.551915024494
  18. : ang2 === -1.5707963267948966
  19. ? -0.551915024494
  20. : 4 / 3 * Math.tan(ang2 / 4);
  21. var x1 = Math.cos(ang1);
  22. var y1 = Math.sin(ang1);
  23. var x2 = Math.cos(ang1 + ang2);
  24. var y2 = Math.sin(ang1 + ang2);
  25. return [
  26. {
  27. x: x1 - y1 * a,
  28. y: y1 + x1 * a
  29. },
  30. {
  31. x: x2 + y2 * a,
  32. y: y2 - x2 * a
  33. },
  34. {
  35. x: x2,
  36. y: y2
  37. }
  38. ];
  39. };
  40. var vectorAngle = function (ux, uy, vx, vy) {
  41. var sign = (ux * vy - uy * vx < 0) ? -1 : 1;
  42. var dot = ux * vx + uy * vy;
  43. if (dot > 1) {
  44. dot = 1;
  45. }
  46. if (dot < -1) {
  47. dot = -1;
  48. }
  49. return sign * Math.acos(dot);
  50. };
  51. var getArcCenter = function (px, py, cx, cy, rx, ry, largeArcFlag, sweepFlag, sinphi, cosphi, pxp, pyp) {
  52. var rxsq = Math.pow(rx, 2);
  53. var rysq = Math.pow(ry, 2);
  54. var pxpsq = Math.pow(pxp, 2);
  55. var pypsq = Math.pow(pyp, 2);
  56. var radicant = (rxsq * rysq) - (rxsq * pypsq) - (rysq * pxpsq);
  57. if (radicant < 0) {
  58. radicant = 0;
  59. }
  60. radicant /= (rxsq * pypsq) + (rysq * pxpsq);
  61. radicant = Math.sqrt(radicant) * (largeArcFlag === sweepFlag ? -1 : 1);
  62. var centerxp = radicant * rx / ry * pyp;
  63. var centeryp = radicant * -ry / rx * pxp;
  64. var centerx = cosphi * centerxp - sinphi * centeryp + (px + cx) / 2;
  65. var centery = sinphi * centerxp + cosphi * centeryp + (py + cy) / 2;
  66. var vx1 = (pxp - centerxp) / rx;
  67. var vy1 = (pyp - centeryp) / ry;
  68. var vx2 = (-pxp - centerxp) / rx;
  69. var vy2 = (-pyp - centeryp) / ry;
  70. var ang1 = vectorAngle(1, 0, vx1, vy1);
  71. var ang2 = vectorAngle(vx1, vy1, vx2, vy2);
  72. if (sweepFlag === 0 && ang2 > 0) {
  73. ang2 -= TAU;
  74. }
  75. if (sweepFlag === 1 && ang2 < 0) {
  76. ang2 += TAU;
  77. }
  78. return [centerx, centery, ang1, ang2];
  79. };
  80. var arcToBezier = function (_a) {
  81. var px = _a.px, py = _a.py, cx = _a.cx, cy = _a.cy, rx = _a.rx, ry = _a.ry, _b = _a.xAxisRotation, xAxisRotation = _b === void 0 ? 0 : _b, _c = _a.largeArcFlag, largeArcFlag = _c === void 0 ? 0 : _c, _d = _a.sweepFlag, sweepFlag = _d === void 0 ? 0 : _d;
  82. var curves = [];
  83. if (rx === 0 || ry === 0) {
  84. return [{ x1: 0, y1: 0, x2: 0, y2: 0, x: cx, y: cy }];
  85. }
  86. var sinphi = Math.sin(xAxisRotation * TAU / 360);
  87. var cosphi = Math.cos(xAxisRotation * TAU / 360);
  88. var pxp = cosphi * (px - cx) / 2 + sinphi * (py - cy) / 2;
  89. var pyp = -sinphi * (px - cx) / 2 + cosphi * (py - cy) / 2;
  90. if (pxp === 0 && pyp === 0) {
  91. return [{ x1: 0, y1: 0, x2: 0, y2: 0, x: cx, y: cy }];
  92. }
  93. rx = Math.abs(rx);
  94. ry = Math.abs(ry);
  95. var lambda = Math.pow(pxp, 2) / Math.pow(rx, 2) +
  96. Math.pow(pyp, 2) / Math.pow(ry, 2);
  97. if (lambda > 1) {
  98. rx *= Math.sqrt(lambda);
  99. ry *= Math.sqrt(lambda);
  100. }
  101. var _e = getArcCenter(px, py, cx, cy, rx, ry, largeArcFlag, sweepFlag, sinphi, cosphi, pxp, pyp), centerx = _e[0], centery = _e[1], ang1 = _e[2], ang2 = _e[3];
  102. // If 'ang2' == 90.0000000001, then `ratio` will evaluate to
  103. // 1.0000000001. This causes `segments` to be greater than one, which is an
  104. // unecessary split, and adds extra points to the bezier curve. To alleviate
  105. // this issue, we round to 1.0 when the ratio is close to 1.0.
  106. var ratio = Math.abs(ang2) / (TAU / 4);
  107. if (Math.abs(1.0 - ratio) < 0.0000001) {
  108. ratio = 1.0;
  109. }
  110. var segments = Math.max(Math.ceil(ratio), 1);
  111. ang2 /= segments;
  112. for (var i = 0; i < segments; i++) {
  113. curves.push(approxUnitArc(ang1, ang2));
  114. ang1 += ang2;
  115. }
  116. return curves.map(function (curve) {
  117. var _a = mapToEllipse(curve[0], rx, ry, cosphi, sinphi, centerx, centery), x1 = _a.x, y1 = _a.y;
  118. var _b = mapToEllipse(curve[1], rx, ry, cosphi, sinphi, centerx, centery), x2 = _b.x, y2 = _b.y;
  119. var _c = mapToEllipse(curve[2], rx, ry, cosphi, sinphi, centerx, centery), x = _c.x, y = _c.y;
  120. return { x1: x1, y1: y1, x2: x2, y2: y2, x: x, y: y };
  121. });
  122. };
  123. export function arcToCubic(x1, y1, rx, ry, angle, LAF, SF, x2, y2) {
  124. var curves = arcToBezier({
  125. px: x1,
  126. py: y1,
  127. cx: x2,
  128. cy: y2,
  129. rx: rx,
  130. ry: ry,
  131. xAxisRotation: angle,
  132. largeArcFlag: LAF,
  133. sweepFlag: SF,
  134. });
  135. return curves.reduce(function (prev, cur) {
  136. var x1 = cur.x1, y1 = cur.y1, x2 = cur.x2, y2 = cur.y2, x = cur.x, y = cur.y;
  137. prev.push(x1, y1, x2, y2, x, y);
  138. return prev;
  139. }, []);
  140. }
  141. //# sourceMappingURL=arc-2-cubic.js.map