ultrahdr icc: update transfer function
Bug: 286444758
Test: jpegr_test.cpp
Manual test:
(1) append icc package to red-noicc.jpeg (attached in
the bug comment #1), then open the image with digital color meter, color measurement should be close to (255, 0, 0).
(2) Dump icc into a file and open the icc file on Mac, read data of each component (wtpt, r/g/bXYZ, r/g/bTRC) that should be the same as the samples in comment #10
Change-Id: I3b4a2b7d283fc143207d2dbce570eadf7568ebec
diff --git a/libs/ultrahdr/icc.cpp b/libs/ultrahdr/icc.cpp
index 1ab3c7c..e41b645 100644
--- a/libs/ultrahdr/icc.cpp
+++ b/libs/ultrahdr/icc.cpp
@@ -19,7 +19,6 @@
#endif
#include <ultrahdr/icc.h>
-#include <ultrahdr/gainmapmath.h>
#include <vector>
#include <utils/Log.h>
@@ -218,8 +217,8 @@
total_length = (((total_length + 2) >> 2) << 2); // 4 aligned
sp<DataStruct> dataStruct = sp<DataStruct>::make(total_length);
dataStruct->write32(Endian_SwapBE32(kTAG_CurveType)); // Type
- dataStruct->write32(0); // Reserved
- dataStruct->write32(Endian_SwapBE32(table_entries)); // Value count
+ dataStruct->write32(0); // Reserved
+ dataStruct->write32(Endian_SwapBE32(table_entries)); // Value count
for (size_t i = 0; i < table_entries; ++i) {
uint16_t value = reinterpret_cast<const uint16_t*>(table_16)[i];
dataStruct->write16(value);
@@ -227,14 +226,30 @@
return dataStruct;
}
-sp<DataStruct> IccHelper::write_trc_tag_for_linear() {
- int total_length = 16;
- sp<DataStruct> dataStruct = sp<DataStruct>::make(total_length);
- dataStruct->write32(Endian_SwapBE32(kTAG_ParaCurveType)); // Type
- dataStruct->write32(0); // Reserved
- dataStruct->write32(Endian_SwapBE16(kExponential_ParaCurveType));
- dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(1.0)));
+sp<DataStruct> IccHelper::write_trc_tag(const TransferFunction& fn) {
+ if (fn.a == 1.f && fn.b == 0.f && fn.c == 0.f
+ && fn.d == 0.f && fn.e == 0.f && fn.f == 0.f) {
+ int total_length = 16;
+ sp<DataStruct> dataStruct = new DataStruct(total_length);
+ dataStruct->write32(Endian_SwapBE32(kTAG_ParaCurveType)); // Type
+ dataStruct->write32(0); // Reserved
+ dataStruct->write32(Endian_SwapBE16(kExponential_ParaCurveType));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.g)));
+ return dataStruct;
+ }
+ int total_length = 40;
+ sp<DataStruct> dataStruct = new DataStruct(total_length);
+ dataStruct->write32(Endian_SwapBE32(kTAG_ParaCurveType)); // Type
+ dataStruct->write32(0); // Reserved
+ dataStruct->write32(Endian_SwapBE16(kGABCDEF_ParaCurveType));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.g)));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.a)));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.b)));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.c)));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.d)));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.e)));
+ dataStruct->write32(Endian_SwapBE32(float_round_to_fixed(fn.f)));
return dataStruct;
}
@@ -349,7 +364,7 @@
// The "B" curve is required.
for (size_t i = 0; i < kNumChannels; ++i) {
- b_curves_data[i] = write_trc_tag_for_linear();
+ b_curves_data[i] = write_trc_tag(kLinear_TransFun);
}
// The "A" curve and CLUT are optional.
@@ -362,7 +377,7 @@
a_curves_offset = clut_offset + clut->getLength();
for (size_t i = 0; i < kNumChannels; ++i) {
- a_curves_data[i] = write_trc_tag_for_linear();
+ a_curves_data[i] = write_trc_tag(kLinear_TransFun);
}
}
@@ -460,9 +475,9 @@
tags.emplace_back(kTAG_bTRC,
write_trc_tag(kTrcTableSize, reinterpret_cast<uint8_t*>(trc_table.data())));
} else {
- tags.emplace_back(kTAG_rTRC, write_trc_tag_for_linear());
- tags.emplace_back(kTAG_gTRC, write_trc_tag_for_linear());
- tags.emplace_back(kTAG_bTRC, write_trc_tag_for_linear());
+ tags.emplace_back(kTAG_rTRC, write_trc_tag(kSRGB_TransFun));
+ tags.emplace_back(kTAG_gTRC, write_trc_tag(kSRGB_TransFun));
+ tags.emplace_back(kTAG_bTRC, write_trc_tag(kSRGB_TransFun));
}
}
diff --git a/libs/ultrahdr/include/ultrahdr/gainmapmath.h b/libs/ultrahdr/include/ultrahdr/gainmapmath.h
index edf152d..6115dfe 100644
--- a/libs/ultrahdr/include/ultrahdr/gainmapmath.h
+++ b/libs/ultrahdr/include/ultrahdr/gainmapmath.h
@@ -51,6 +51,23 @@
typedef Color (*ColorTransformFn)(Color);
typedef float (*ColorCalculationFn)(Color);
+// A transfer function mapping encoded values to linear values,
+// represented by this 7-parameter piecewise function:
+//
+// linear = sign(encoded) * (c*|encoded| + f) , 0 <= |encoded| < d
+// = sign(encoded) * ((a*|encoded| + b)^g + e), d <= |encoded|
+//
+// (A simple gamma transfer function sets g to gamma and a to 1.)
+typedef struct TransferFunction {
+ float g, a,b,c,d,e,f;
+} TransferFunction;
+
+static constexpr TransferFunction kSRGB_TransFun =
+ { 2.4f, (float)(1/1.055), (float)(0.055/1.055), (float)(1/12.92), 0.04045f, 0.0f, 0.0f };
+
+static constexpr TransferFunction kLinear_TransFun =
+ { 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
+
inline Color operator+=(Color& lhs, const Color& rhs) {
lhs.r += rhs.r;
lhs.g += rhs.g;
diff --git a/libs/ultrahdr/include/ultrahdr/icc.h b/libs/ultrahdr/include/ultrahdr/icc.h
index 7f047f8..971b267 100644
--- a/libs/ultrahdr/include/ultrahdr/icc.h
+++ b/libs/ultrahdr/include/ultrahdr/icc.h
@@ -17,6 +17,7 @@
#ifndef ANDROID_ULTRAHDR_ICC_H
#define ANDROID_ULTRAHDR_ICC_H
+#include <ultrahdr/gainmapmath.h>
#include <ultrahdr/jpegr.h>
#include <ultrahdr/jpegrutils.h>
#include <utils/RefBase.h>
@@ -222,7 +223,7 @@
const ultrahdr_color_gamut gamut);
static sp<DataStruct> write_xyz_tag(float x, float y, float z);
static sp<DataStruct> write_trc_tag(const int table_entries, const void* table_16);
- static sp<DataStruct> write_trc_tag_for_linear();
+ static sp<DataStruct> write_trc_tag(const TransferFunction& fn);
static float compute_tone_map_gain(const ultrahdr_transfer_function tf, float L);
static sp<DataStruct> write_cicp_tag(uint32_t color_primaries,
uint32_t transfer_characteristics);