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diff --git a/lib/ultrahdr.h b/lib/ultrahdr.h
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+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ULTRAHDR_ULTRAHDR_H
+#define ULTRAHDR_ULTRAHDR_H
+
+#include <string>
+
+namespace ultrahdr {
+// Color gamuts for image data
+typedef enum {
+  ULTRAHDR_COLORGAMUT_UNSPECIFIED = -1,
+  ULTRAHDR_COLORGAMUT_BT709,
+  ULTRAHDR_COLORGAMUT_P3,
+  ULTRAHDR_COLORGAMUT_BT2100,
+  ULTRAHDR_COLORGAMUT_MAX = ULTRAHDR_COLORGAMUT_BT2100,
+} ultrahdr_color_gamut;
+
+// Transfer functions for image data
+// TODO: TF LINEAR is deprecated, remove this enum and the code surrounding it.
+typedef enum {
+  ULTRAHDR_TF_UNSPECIFIED = -1,
+  ULTRAHDR_TF_LINEAR = 0,
+  ULTRAHDR_TF_HLG = 1,
+  ULTRAHDR_TF_PQ = 2,
+  ULTRAHDR_TF_SRGB = 3,
+  ULTRAHDR_TF_MAX = ULTRAHDR_TF_SRGB,
+} ultrahdr_transfer_function;
+
+// Target output formats for decoder
+typedef enum {
+  ULTRAHDR_OUTPUT_UNSPECIFIED = -1,
+  ULTRAHDR_OUTPUT_SDR,         // SDR in RGBA_8888 color format
+  ULTRAHDR_OUTPUT_HDR_LINEAR,  // HDR in F16 color format (linear)
+  ULTRAHDR_OUTPUT_HDR_PQ,      // HDR in RGBA_1010102 color format (PQ transfer function)
+  ULTRAHDR_OUTPUT_HDR_HLG,     // HDR in RGBA_1010102 color format (HLG transfer function)
+  ULTRAHDR_OUTPUT_MAX = ULTRAHDR_OUTPUT_HDR_HLG,
+} ultrahdr_output_format;
+
+/*
+ * Holds information for gain map related metadata.
+ *
+ * Not: all values stored in linear. This differs from the metadata encoding in XMP, where
+ * maxContentBoost (aka gainMapMax), minContentBoost (aka gainMapMin), hdrCapacityMin, and
+ * hdrCapacityMax are stored in log2 space.
+ */
+struct ultrahdr_metadata_struct {
+  // Ultra HDR format version
+  std::string version;
+  // Max Content Boost for the map
+  float maxContentBoost;
+  // Min Content Boost for the map
+  float minContentBoost;
+  // Gamma of the map data
+  float gamma;
+  // Offset for SDR data in map calculations
+  float offsetSdr;
+  // Offset for HDR data in map calculations
+  float offsetHdr;
+  // HDR capacity to apply the map at all
+  float hdrCapacityMin;
+  // HDR capacity to apply the map completely
+  float hdrCapacityMax;
+};
+typedef struct ultrahdr_metadata_struct* ultrahdr_metadata_ptr;
+
+}  // namespace ultrahdr
+
+#endif  // ULTRAHDR_ULTRAHDR_H