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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 "SkColorSpaceXform.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;
}
// Expand range from 0-1 to 0-255, then convert.
static inline uint8_t clamp_normalized_float_to_byte(float v) {
// The ordering of the logic is a little strange here in order
// to make sure we convert NaNs to 0.
v = v * 255.0f;
if (v >= 254.5f) {
return 255;
} else if (v >= 0.5f) {
return (uint8_t) (v + 0.5f);
} else {
return 0;
}
}
static inline float clamp_0_1(float v) {
// The ordering of the logic is a little strange here in order
// to make sure we convert NaNs to 0.
if (v >= 1.0f) {
return 1.0f;
} else if (v >= 0.0f) {
return v;
} else {
return 0.0f;
}
}
/**
* Invert table lookup. Ex: what indices corresponds to the input values?
* This will have strange results when the table is not increasing.
* But any sane gamma function will be increasing.
* @param outTableFloat Destination table for float (0-1) results. Can be nullptr if not wanted.
* @param outTableByte Destination table for byte (0-255) results. Can be nullptr if not wanted.
* @param outTableSize Number of elements in |outTableFloat| or |outTableBytes|
* @param inTable The source table to invert
* @param inTableSize The number of elements in |inTable|
*/
static inline void invert_table_gamma(float* outTableFloat, uint8_t* outTableByte,
int outTableSize, const float* inTable, int inTableSize) {
// should never have a gamma table this small anyway, 0/1 are either not allowed
// or imply a non-table gamma such as linear/exponential
SkASSERT(inTableSize >= 2);
int inIndex = 1;
for (int outIndex = 0; outIndex < outTableSize; ++outIndex) {
const float input = outIndex / (outTableSize - 1.0f);
while (inIndex < inTableSize - 1 && inTable[inIndex] < input) {
++inIndex;
}
const float diff = input - inTable[inIndex - 1];
const float distance = inTable[inIndex] - inTable[inIndex - 1];
const float normalizedIndex = (inIndex - 1) + diff / distance;
const float index = normalizedIndex / (inTableSize - 1);
if (outTableByte) {
outTableByte[outIndex] = clamp_normalized_float_to_byte(index);
}
if (outTableFloat) {
outTableFloat[outIndex] = clamp_0_1(index);
}
}
}
static inline SkColorSpaceXform::ColorFormat select_xform_format(SkColorType colorType) {
switch (colorType) {
case kRGBA_8888_SkColorType:
return SkColorSpaceXform::kRGBA_8888_ColorFormat;
case kBGRA_8888_SkColorType:
return SkColorSpaceXform::kBGRA_8888_ColorFormat;
case kRGBA_F16_SkColorType:
return SkColorSpaceXform::kRGBA_F16_ColorFormat;
case kRGB_565_SkColorType:
return SkColorSpaceXform::kBGR_565_ColorFormat;
default:
SkASSERT(false);
return SkColorSpaceXform::kRGBA_8888_ColorFormat;
}
}
#endif
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