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/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkColorSpaceXformPriv_DEFINED
#define SkColorSpaceXformPriv_DEFINED
#include "SkColorSpace_Base.h"
#include "SkHalf.h"
#include "SkSRGB.h"
#define SkCSXformPrintfDefined 0
#define SkCSXformPrintf(...)
// Interpolating lookup in a variably sized table.
static inline float interp_lut(float input, const float* table, int tableSize) {
float index = input * (tableSize - 1);
float diff = index - sk_float_floor2int(index);
return table[(int) sk_float_floor2int(index)] * (1.0f - diff) +
table[(int) sk_float_ceil2int(index)] * diff;
}
// Inverse table lookup. Ex: what index corresponds to the input value? This will
// have strange results when the table is non-increasing. But any sane gamma
// function will be increasing.
static inline float inverse_interp_lut(float input, const float* table, int tableSize) {
if (input <= table[0]) {
return table[0];
} else if (input >= table[tableSize - 1]) {
return 1.0f;
}
for (int i = 1; i < tableSize; i++) {
if (table[i] >= input) {
// We are guaranteed that input is greater than table[i - 1].
float diff = input - table[i - 1];
float distance = table[i] - table[i - 1];
float index = (i - 1) + diff / distance;
return index / (tableSize - 1);
}
}
// Should be unreachable, since we'll return before the loop if input is
// larger than the last entry.
SkASSERT(false);
return 0.0f;
}
#undef AI
#endif
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