Add preliminary support for loading HDR images

The Netflix HDR sample images are loading correctly.
Currently the HDR support is limited to SMPTE ST 2084 (BT.2100 PQ).

It is unclear how the HDR support should work with premultiplied alpha
images.
I filed an issue in the av1-avif repository for clarification on that:
AOMediaCodec/av1-avif#197

src/common/AvifFormat.cpp

@@ -77,7 +77,9 @@ namespace
     {
         globals->context = nullptr;
         globals->imageHandle = nullptr;
+        globals->imageHandleNclxProfile = nullptr;
         globals->image = nullptr;
+        globals->imageHandleProfileType = heif_color_profile_type_not_present;
         globals->saveOptions.quality = 85;
         globals->saveOptions.chromaSubsampling = ChromaSubsampling::Yuv422;
         globals->saveOptions.compressionSpeed = CompressionSpeed::Default;

src/common/AvifFormat.h

@@ -63,7 +63,9 @@ struct Globals
 {
     heif_context* context;
     heif_image_handle* imageHandle;
+    heif_color_profile_nclx* imageHandleNclxProfile;
     heif_image* image;
+    heif_color_profile_type imageHandleProfileType;
 
     SaveUIOptions saveOptions;
     bool libheifInitialized;

src/common/AvifFormat.r

@@ -95,7 +95,7 @@ resource 'PiPL' (ResourceID, plugInName " PiPL", purgeable)
             noLABColor
         },
 
-        EnableInfo { "in (PSHOP_ImageMode, RGBMode, RGB48Mode, GrayScaleMode, Gray16Mode)" },
+        EnableInfo { "in (PSHOP_ImageMode, RGBMode, RGB48Mode, GrayScaleMode, Gray16Mode, RGB96Mode, Gray32Mode)" },
 
         PlugInMaxSize { 1073741824, 1073741824 },
 

src/common/ColorProfileGeneration.cpp

@@ -345,7 +345,10 @@ void SetIccProfileFromNclx(FormatRecord* formatRecord, const heif_color_profile_
                 toneCurve.reset(cmsBuildParametricToneCurve(context.get(), 4, Parameters));
                 description = L"Grayscale (sRGB TRC)";
             }
-            else if (transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_709_5)
+            else if (transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_709_5 ||
+                     transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_601_6 ||
+                     transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_2020_2_10bit ||
+                     transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_2020_2_12bit)
             {
                 cmsFloat64Number Parameters[5]
                 {
@@ -357,7 +360,26 @@ void SetIccProfileFromNclx(FormatRecord* formatRecord, const heif_color_profile_
                 };
 
                 toneCurve.reset(cmsBuildParametricToneCurve(context.get(), 4, Parameters));
-                description = L"Grayscale (Rec. 709 TRC)";
+
+                switch (primaries)
+                {
+                case heif_color_primaries_ITU_R_BT_2020_2_and_2100_0:
+                    description = L"Grayscale (BT. 2020)";
+                    break;
+                case heif_color_primaries_ITU_R_BT_709_5:
+                case heif_color_primaries_ITU_R_BT_470_6_System_M:
+                case heif_color_primaries_ITU_R_BT_470_6_System_B_G:
+                case heif_color_primaries_ITU_R_BT_601_6:
+                case heif_color_primaries_SMPTE_240M:
+                case heif_color_primaries_generic_film:
+                case heif_color_primaries_SMPTE_ST_428_1:
+                case heif_color_primaries_SMPTE_RP_431_2:
+                case heif_color_primaries_SMPTE_EG_432_1:
+                case heif_color_primaries_EBU_Tech_3213_E:
+                default:
+                    description = L"Grayscale (Rec. 709 TRC)";
+                    break;
+                }
             }
 
             if (toneCurve && description != nullptr)
@@ -437,6 +459,51 @@ void SetIccProfileFromNclx(FormatRecord* formatRecord, const heif_color_profile_
                         description);
                 }
             }
+            else if (primaries == heif_color_primaries_ITU_R_BT_2020_2_and_2100_0)
+            {
+                const cmsCIExyY whitepoint = { 0.3127, 0.3290, 1.0f }; // D65
+                const cmsCIExyYTRIPLE rgbPrimaries =
+                {
+                    { 0.708, 0.292, 1.0 },
+                    { 0.170, 0.797, 1.0 },
+                    { 0.131, 0.046, 1.0 }
+                };
+
+                ScopedLcmsToneCurve toneCurve;
+                const wchar_t* description = nullptr;
+
+                if (linear)
+                {
+                    toneCurve.reset(cmsBuildGamma(context.get(), 1.0));
+                    description = L"BT. 2020 (Linear RGB Profile)";
+                }
+                else if (transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_2020_2_10bit ||
+                         transferCharacteristics == heif_transfer_characteristic_ITU_R_BT_2020_2_12bit)
+                {
+                    // BT. 2020 uses the same transfer curve as Rec. 709.
+                    cmsFloat64Number Parameters[5]
+                    {
+                        1.0 / 0.45,
+                        1.0 / 1.099296826809442,
+                        1.0 - 1 / 1.099296826809442,
+                        1.0 / 4.5,
+                        4.5 * 0.018053968510807,
+                    };
+
+                    toneCurve.reset(cmsBuildParametricToneCurve(context.get(), 4, Parameters));
+                    description = L"BT. 2020";
+                }
+
+                if (toneCurve && description != nullptr)
+                {
+                    profile = BuildRGBProfile(
+                        context.get(),
+                        &whitepoint,
+                        &rgbPrimaries,
+                        toneCurve.get(),
+                        description);
+                }
+            }
 
             if (profile)
             {

src/common/ColorTransfer.cpp

@@ -0,0 +1,99 @@
+/*
+ * This file is part of avif-format, an AV1 Image (AVIF) file format
+ * plug-in for Adobe Photoshop(R).
+ *
+ * Copyright (c) 2021, 2022 Nicholas Hayes
+ *
+ * avif-format is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * avif-format is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with avif-format.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "ColorTransfer.h"
+#include <stdexcept>
+
+namespace
+{
+    // The sRGB reference viewing environment has a maximum luminance level of 80 nits
+    // See the 'Screen luminance level' value in the sRGB reference viewing environment table
+    // https://en.wikipedia.org/wiki/SRGB#Viewing_environment
+    constexpr float srgbMaxLuminanceLevel = 80.0f;
+    // PQ (SMPTE ST 2084) has a maximum luminance level of 10000 nits
+    // https://en.wikipedia.org/wiki/Perceptual_quantizer
+    constexpr float pqMaxLuminanceLevel = 10000;
+
+    inline float LinearToPQ(float normalizedLinearValue)
+    {
+        // These constant values are taken from the Perceptual quantizer article on Wikipedia
+        // https://en.wikipedia.org/wiki/Perceptual_quantizer
+        constexpr float m1 = 2610.0f / 16384.0f;
+        constexpr float m2 = 2523.0f / 4096.0f * 128.0f;
+        constexpr float c1 = 3424.0f / 4096.0f; // c3 - c2 + 1
+        constexpr float c2 = 2413.0f / 4096.0f * 32.0f;
+        constexpr float c3 = 2392.0f / 4096.0f * 32.0f;
+
+        if (normalizedLinearValue < 0.0f)
+        {
+            return 0.0f;
+        }
+
+        const float x = powf(normalizedLinearValue, m1);
+        const float pq = powf((c1 + c2 * x) / (1.0f + c3 * x), m2);
+
+        return pq;
+    }
+
+    inline float PQToLinear(float value)
+    {
+        // These constant values are taken from the Perceptual quantizer article on Wikipedia
+        // https://en.wikipedia.org/wiki/Perceptual_quantizer
+        constexpr float m1 = 2610.0f / 16384.0f;
+        constexpr float m2 = 2523.0f / 4096.0f * 128.0f;
+        constexpr float c1 = 3424.0f / 4096.0f; // c3 - c2 + 1
+        constexpr float c2 = 2413.0f / 4096.0f * 32.0f;
+        constexpr float c3 = 2392.0f / 4096.0f * 32.0f;
+
+        if (value < 0.0f)
+        {
+            return 0.0f;
+        }
+
+        const float x = powf(value, 1.0f / m2);
+        const float normalizedLinear = powf(std::max(x - c1, 0.0f) / (c2 - c3 * x), 1.0f / m1);
+
+        // We have to adjust for the difference in the maximum luminance level between
+        // PQ and sRGB, otherwise the image is too dark.
+        return normalizedLinear * (pqMaxLuminanceLevel / srgbMaxLuminanceLevel);
+    }
+}
+
+float TransferCurveToLinear(float value, ColorTransferCurveType curveType)
+{
+    switch (curveType)
+    {
+    case ColorTransferCurveType::PQ:
+        return PQToLinear(value);
+    default:
+        throw std::runtime_error("Unsupported color transfer curve type.");
+    }
+}
+
+float LinearToTransferCurve(float value, ColorTransferCurveType curveType)
+{
+    switch (curveType)
+    {
+    case ColorTransferCurveType::PQ:
+        return LinearToPQ(value);
+    default:
+        throw std::runtime_error("Unsupported color transfer curve type.");
+    }
+}

src/common/ColorTransfer.h

@@ -0,0 +1,36 @@
+/*
+ * This file is part of avif-format, an AV1 Image (AVIF) file format
+ * plug-in for Adobe Photoshop(R).
+ *
+ * Copyright (c) 2021, 2022 Nicholas Hayes
+ *
+ * avif-format is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * avif-format is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with avif-format.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef COLORTRANSFER_H
+#define COLORTRANSFER_H
+
+#include <algorithm>
+#include <math.h>
+
+enum class ColorTransferCurveType
+{
+    PQ
+};
+
+float TransferCurveToLinear(float value, ColorTransferCurveType curveType);
+
+float LinearToTransferCurve(float value, ColorTransferCurveType curveType);
+
+#endif // !COLORTRANSFER_H