1
2/*
3 * Copyright 2010 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#include "SkMath.h"
11#include "SkScalar.h"
12
13SkScalar SkScalarInterpFunc(SkScalar searchKey, const SkScalar keys[],
14                            const SkScalar values[], int length) {
15    SkASSERT(length > 0);
16    SkASSERT(keys != NULL);
17    SkASSERT(values != NULL);
18#ifdef SK_DEBUG
19    for (int i = 1; i < length; i++)
20        SkASSERT(keys[i] >= keys[i-1]);
21#endif
22    int right = 0;
23    while (right < length && searchKey > keys[right])
24        right++;
25    // Could use sentinel values to eliminate conditionals, but since the
26    // tables are taken as input, a simpler format is better.
27    if (length == right)
28        return values[length-1];
29    if (0 == right)
30        return values[0];
31    // Otherwise, interpolate between right - 1 and right.
32    SkScalar rightKey = keys[right];
33    SkScalar leftKey = keys[right-1];
34    SkScalar fract = SkScalarDiv(searchKey-leftKey,rightKey-leftKey);
35    return SkScalarInterp(values[right-1], values[right], fract);
36}
37