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| 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 } |
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