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 "include/core/SkMath.h"
10 #include "include/core/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-1] <= keys[i]);
20 }
21 #endif
22 int right = 0;
23 while (right < length && keys[right] < searchKey) {
24 ++right;
25 }
26 // Could use sentinel values to eliminate conditionals, but since the
27 // tables are taken as input, a simpler format is better.
28 if (right == length) {
29 return values[length-1];
30 }
31 if (right == 0) {
32 return values[0];
33 }
34 // Otherwise, interpolate between right - 1 and right.
35 SkScalar leftKey = keys[right-1];
36 SkScalar rightKey = keys[right];
37 SkScalar fract = (searchKey - leftKey) / (rightKey - leftKey);
38 return SkScalarInterp(values[right-1], values[right], fract);
39 }
40