From 2c10dfc7aa259ad0fd5f3eab8879e870e77fd667 Mon Sep 17 00:00:00 2001 From: Mattias Andrée Date: Sun, 6 Apr 2014 00:44:00 +0200 Subject: m + fix cubic interpolation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Mattias Andrée --- src/interpolation.py | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'src/interpolation.py') diff --git a/src/interpolation.py b/src/interpolation.py index 0d16838..e81c93c 100644 --- a/src/interpolation.py +++ b/src/interpolation.py @@ -47,13 +47,14 @@ def linearly_interpolate_ramp(r, g, b): return (R, G, B) -def cubicly_interpolate_ramp(r, g, b): +def cubicly_interpolate_ramp(r, g, b, tension = 0): # TODO demo and document tension parameter ''' Interpolate ramps to the size of the output axes using cubic Hermite spline @param r:list The red colour curves @param g:list The green colour curves @param b:list The blue colour curves + @param tension:float A [0, 1] value of the tension @return :(r:list, g:list, b:list) The input parameters extended to sizes of `o_size`, or their original size, whatever is larger. ''' @@ -61,8 +62,8 @@ def cubicly_interpolate_ramp(r, g, b): R, G, B = C(r), C(g), C(b) # Basis functions h00 = lambda t : (1 + 2 * t) * (1 - t) ** 2 - h01 = lambda t : t * (1 - t) ** 2 - h10 = lambda t : t ** 2 * (3 - 2 * t) + h10 = lambda t : t * (1 - t) ** 2 + h01 = lambda t : t ** 2 * (3 - 2 * t) h11 = lambda t : t ** 2 * (t - 1) def tangent(values, index, last): ''' @@ -77,6 +78,8 @@ def cubicly_interpolate_ramp(r, g, b): if index == 0: return values[1] - values[0] if index == last: return values[last] - values[last - 1] return (values[index + 1] - values[index - 1]) / 2 + # Tension coefficent + c_ = 1 - tension # Interpolate each curve for small, large in ((r, R), (g, G), (b, B)): small_, large_ = len(small) - 1, len(large) - 1 @@ -90,7 +93,7 @@ def cubicly_interpolate_ramp(r, g, b): # Points pj, pk = small[j], small[k] # Tangents - mj, mk = tangent(small, j, small_), tangent(small, k, small_) + mj, mk = c_ * tangent(small, j, small_), c_ * tangent(small, k, small_) # Interpolation large[i] = h00(w) * pj + h10(w) * mj + h01(w) * pk + h11(w) * mk ## Check local monotonicity -- cgit v1.2.3-70-g09d2