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天文台pc/tianwentai-ui/node_modules/d3-interpolate/src/zoom.js 1.61 KB
bc518174   王天杨   提交两个项目文件
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  var epsilon2 = 1e-12;
  
  function cosh(x) {
    return ((x = Math.exp(x)) + 1 / x) / 2;
  }
  
  function sinh(x) {
    return ((x = Math.exp(x)) - 1 / x) / 2;
  }
  
  function tanh(x) {
    return ((x = Math.exp(2 * x)) - 1) / (x + 1);
  }
  
  export default (function zoomRho(rho, rho2, rho4) {
  
    // p0 = [ux0, uy0, w0]
    // p1 = [ux1, uy1, w1]
    function zoom(p0, p1) {
      var ux0 = p0[0], uy0 = p0[1], w0 = p0[2],
          ux1 = p1[0], uy1 = p1[1], w1 = p1[2],
          dx = ux1 - ux0,
          dy = uy1 - uy0,
          d2 = dx * dx + dy * dy,
          i,
          S;
  
      // Special case for u0 ≅ u1.
      if (d2 < epsilon2) {
        S = Math.log(w1 / w0) / rho;
        i = function(t) {
          return [
            ux0 + t * dx,
            uy0 + t * dy,
            w0 * Math.exp(rho * t * S)
          ];
        }
      }
  
      // General case.
      else {
        var d1 = Math.sqrt(d2),
            b0 = (w1 * w1 - w0 * w0 + rho4 * d2) / (2 * w0 * rho2 * d1),
            b1 = (w1 * w1 - w0 * w0 - rho4 * d2) / (2 * w1 * rho2 * d1),
            r0 = Math.log(Math.sqrt(b0 * b0 + 1) - b0),
            r1 = Math.log(Math.sqrt(b1 * b1 + 1) - b1);
        S = (r1 - r0) / rho;
        i = function(t) {
          var s = t * S,
              coshr0 = cosh(r0),
              u = w0 / (rho2 * d1) * (coshr0 * tanh(rho * s + r0) - sinh(r0));
          return [
            ux0 + u * dx,
            uy0 + u * dy,
            w0 * coshr0 / cosh(rho * s + r0)
          ];
        }
      }
  
      i.duration = S * 1000 * rho / Math.SQRT2;
  
      return i;
    }
  
    zoom.rho = function(_) {
      var _1 = Math.max(1e-3, +_), _2 = _1 * _1, _4 = _2 * _2;
      return zoomRho(_1, _2, _4);
    };
  
    return zoom;
  })(Math.SQRT2, 2, 4);