1 /*
2 * Copyright 2010 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8
9 #include "SkMath.h"
10 #include "SkScalar.h"
11
SkScalarInterpFunc(SkScalar searchKey,const SkScalar keys[],const SkScalar values[],int length)12 SkScalar SkScalarInterpFunc(SkScalar searchKey, const SkScalar keys[],
13 const SkScalar values[], int length) {
14 SkASSERT(length > 0);
15 SkASSERT(keys != nullptr);
16 SkASSERT(values != nullptr);
17 #ifdef SK_DEBUG
18 for (int i = 1; i < length; i++)
19 SkASSERT(keys[i] >= keys[i-1]);
20 #endif
21 int right = 0;
22 while (right < length && searchKey > keys[right])
23 right++;
24 // Could use sentinel values to eliminate conditionals, but since the
25 // tables are taken as input, a simpler format is better.
26 if (length == right)
27 return values[length-1];
28 if (0 == right)
29 return values[0];
30 // Otherwise, interpolate between right - 1 and right.
31 SkScalar rightKey = keys[right];
32 SkScalar leftKey = keys[right-1];
33 SkScalar fract = (searchKey - leftKey) / (rightKey - leftKey);
34 return SkScalarInterp(values[right-1], values[right], fract);
35 }
36