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/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "Curve.h"
#include "PortableMath.h"
#include "TransferFunction.h"
#include <assert.h>
static float minus_1_ulp(float x) {
int32_t bits;
memcpy(&bits, &x, sizeof(bits));
bits = bits - 1;
memcpy(&x, &bits, sizeof(bits));
return x;
}
float skcms_eval_curve(const skcms_Curve* curve, float x) {
if (curve->table_entries == 0) {
return skcms_TransferFunction_eval(&curve->parametric, x);
}
float ix = fmaxf_(0, fminf_(x, 1)) * (curve->table_entries - 1);
int lo = (int) ix,
hi = (int)minus_1_ulp(ix + 1.0f);
float t = ix - (float)lo;
float l, h;
if (curve->table_8) {
l = curve->table_8[lo] * (1/255.0f);
h = curve->table_8[hi] * (1/255.0f);
} else {
uint16_t be_l, be_h;
memcpy(&be_l, curve->table_16 + 2*lo, 2);
memcpy(&be_h, curve->table_16 + 2*hi, 2);
uint16_t le_l = ((be_l << 8) | (be_l >> 8)) & 0xffff;
uint16_t le_h = ((be_h << 8) | (be_h >> 8)) & 0xffff;
l = le_l * (1/65535.0f);
h = le_h * (1/65535.0f);
}
return l + (h-l)*t;
}
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