1 /*
2 * Copyright 2010, The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "SkScalar.h"
18
SkScalarInterpFunc(SkScalar searchKey,const SkScalar keys[],const SkScalar values[],int length)19 SkScalar SkScalarInterpFunc(SkScalar searchKey, const SkScalar keys[],
20 const SkScalar values[], int length) {
21 SkASSERT(length > 0);
22 SkASSERT(keys != NULL);
23 SkASSERT(values != NULL);
24 #ifdef SK_DEBUG
25 for (int i = 1; i < length; i++)
26 SkASSERT(keys[i] >= keys[i-1]);
27 #endif
28 int right = 0;
29 while (right < length && searchKey > keys[right])
30 right++;
31 // Could use sentinel values to eliminate conditionals, but since the
32 // tables are taken as input, a simpler format is better.
33 if (length == right)
34 return values[length-1];
35 if (0 == right)
36 return values[0];
37 // Otherwise, interpolate between right - 1 and right.
38 SkScalar rightKey = keys[right];
39 SkScalar leftKey = keys[right-1];
40 SkScalar fract = SkScalarDiv(searchKey-leftKey,rightKey-leftKey);
41 return SkScalarInterp(values[right-1], values[right], fract);
42 }
43