Simple PKM image decoder.

third_party/etc1/etc1.h

Index: third_party/etc1/etc1.h
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+// Copyright 2009 Google Inc.
+//
+// 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.
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+// This is a fork of the AOSP project ETC1 codec. The original code can be found
+// at the following web site:
+// https://android.googlesource.com/platform/frameworks/native/+/master/opengl/libs/ETC1/
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+#ifndef __etc1_h__
+#define __etc1_h__
+
+#define ETC1_ENCODED_BLOCK_SIZE 8
+#define ETC1_DECODED_BLOCK_SIZE 48
+
+#ifndef ETC1_RGB8_OES
+#define ETC1_RGB8_OES 0x8D64
+#endif
+
+typedef unsigned char etc1_byte;
+typedef int etc1_bool;
+typedef unsigned int etc1_uint32;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Encode a block of pixels.
+//
+// pIn is a pointer to a ETC_DECODED_BLOCK_SIZE array of bytes that represent a
+// 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
+// value of pixel (x, y).
+//
+// validPixelMask is a 16-bit mask where bit (1 << (x + y * 4)) indicates whether
+// the corresponding (x,y) pixel is valid. Invalid pixel color values are ignored when compressing.
+//
+// pOut is an ETC1 compressed version of the data.
+
+void etc1_encode_block(const etc1_byte* pIn, etc1_uint32 validPixelMask, etc1_byte* pOut);
+
+// Decode a block of pixels.
+//
+// pIn is an ETC1 compressed version of the data.
+//
+// pOut is a pointer to a ETC_DECODED_BLOCK_SIZE array of bytes that represent a
+// 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
+// value of pixel (x, y).
+
+void etc1_decode_block(const etc1_byte* pIn, etc1_byte* pOut);
+
+// Return the size of the encoded image data (does not include size of PKM header).
+
+etc1_uint32 etc1_get_encoded_data_size(etc1_uint32 width, etc1_uint32 height);
+
+// Encode an entire image.
+// pIn - pointer to the image data. Formatted such that
+//       pixel (x,y) is at pIn + pixelSize * x + stride * y;
+// pOut - pointer to encoded data. Must be large enough to store entire encoded image.
+// pixelSize can be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 3 is a GL_BYTE RGB image.
+// returns non-zero if there is an error.
+
+int etc1_encode_image(const etc1_byte* pIn, etc1_uint32 width, etc1_uint32 height,
+        etc1_uint32 pixelSize, etc1_uint32 stride, etc1_byte* pOut);
+
+// Decode an entire image.
+// pIn - pointer to encoded data.
+// pOut - pointer to the image data. Will be written such that
+//        pixel (x,y) is at pIn + pixelSize * x + stride * y. Must be
+//        large enough to store entire image.
+// pixelSize can be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 3 is a GL_BYTE RGB image.
+// returns non-zero if there is an error.
+
+int etc1_decode_image(const etc1_byte* pIn, etc1_byte* pOut,
+        etc1_uint32 width, etc1_uint32 height,
+        etc1_uint32 pixelSize, etc1_uint32 stride);
+
+// Size of a PKM header, in bytes.
+
+#define ETC_PKM_HEADER_SIZE 16
+
+// Format a PKM header
+
+void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height);
+
+// Check if a PKM header is correctly formatted.
+
+etc1_bool etc1_pkm_is_valid(const etc1_byte* pHeader);
+
+// Read the image width from a PKM header
+
+etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader);
+
+// Read the image height from a PKM header
+
+etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif