1 function interp(A, B, t) { 2 return A + (B - A) * t; 3 } 4 5 function interp_cubic_coords(x1, x2, x3, x4, t) 6 { 7 var ab = interp(x1, x2, t); 8 var bc = interp(x2, x3, t); 9 var cd = interp(x3, x4, t); 10 var abc = interp(ab, bc, t); 11 var bcd = interp(bc, cd, t); 12 var abcd = interp(abc, bcd, t); 13 return abcd; 14 } 15 16 // FIXME : only works for path with single cubic 17 function path_partial(value, path) { 18 assert(isArray(path)); 19 var out = []; 20 for (var cIndex = 0; cIndex < path.length; ++cIndex) { 21 out[cIndex] = {}; 22 var curveKey = Object.keys(path[cIndex])[0]; 23 var curve = path[cIndex][curveKey]; 24 var outArray; 25 switch (curveKey) { 26 case "cubic": 27 var x1 = curve[0], y1 = curve[1], x2 = curve[2], y2 = curve[3]; 28 var x3 = curve[4], y3 = curve[5], x4 = curve[6], y4 = curve[7]; 29 var t1 = 0, t2 = value; 30 var ax = interp_cubic_coords(x1, x2, x3, x4, t1); 31 var ay = interp_cubic_coords(y1, y2, y3, y4, t1); 32 var ex = interp_cubic_coords(x1, x2, x3, x4, (t1*2+t2)/3); 33 var ey = interp_cubic_coords(y1, y2, y3, y4, (t1*2+t2)/3); 34 var fx = interp_cubic_coords(x1, x2, x3, x4, (t1+t2*2)/3); 35 var fy = interp_cubic_coords(y1, y2, y3, y4, (t1+t2*2)/3); 36 var dx = interp_cubic_coords(x1, x2, x3, x4, t2); 37 var dy = interp_cubic_coords(y1, y2, y3, y4, t2); 38 var mx = ex * 27 - ax * 8 - dx; 39 var my = ey * 27 - ay * 8 - dy; 40 var nx = fx * 27 - ax - dx * 8; 41 var ny = fy * 27 - ay - dy * 8; 42 var bx = (mx * 2 - nx) / 18; 43 var by = (my * 2 - ny) / 18; 44 var cx = (nx * 2 - mx) / 18; 45 var cy = (ny * 2 - my) / 18; 46 outArray = [ 47 ax, ay, bx, by, cx, cy, dx, dy 48 ]; 49 break; 50 default: 51 assert(0); // unimplemented 52 } 53 out[cIndex][curveKey] = outArray; 54 } 55 return out; 56 } 57 58 function interp_paths(value, paths) { 59 assert(isArray(paths)); 60 assert(paths.length == 2); 61 var curves0 = paths[0]; 62 assert(isArray(curves0)); 63 var curves1 = paths[1]; 64 assert(isArray(curves1)); 65 assert(curves0.length == curves1.length); 66 var out = []; 67 for (var cIndex = 0; cIndex < curves0.length; ++cIndex) { 68 out[cIndex] = {}; 69 var curve0Key = Object.keys(curves0[cIndex])[0]; 70 var curve1Key = Object.keys(curves1[cIndex])[0]; 71 assert(curve0Key == curve1Key); 72 var curve0 = curves0[cIndex][curve0Key]; 73 var curve1 = curves1[cIndex][curve1Key]; 74 assert(isArray(curve0)); 75 assert(isArray(curve1)); 76 assert(curve0.length == curve1.length); 77 var outArray = []; 78 for (var i = 0; i < curve1.length; ++i) { 79 outArray[i] = curve0[i] + (curve1[i] - curve0[i]) * value; 80 } 81 out[cIndex][curve0Key] = outArray; 82 } 83 return out; 84 } 85
