1// Copyright 2009 Google Inc.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15#ifndef __etc1_h__
16#define __etc1_h__
17
18#define ETC1_ENCODED_BLOCK_SIZE 8
19#define ETC1_DECODED_BLOCK_SIZE 48
20
21#ifndef ETC1_RGB8_OES
22#define ETC1_RGB8_OES 0x8D64
23#endif
24
25typedef unsigned char etc1_byte;
26typedef int etc1_bool;
27typedef unsigned int etc1_uint32;
28
29#ifdef __cplusplus
30extern "C" {
31#endif
32
33// Encode a block of pixels.
34//
35// pIn is a pointer to a ETC_DECODED_BLOCK_SIZE array of bytes that represent a
36// 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
37// value of pixel (x, y).
38//
39// validPixelMask is a 16-bit mask where bit (1 << (x + y * 4)) indicates whether
40// the corresponding (x,y) pixel is valid. Invalid pixel color values are ignored when compressing.
41//
42// pOut is an ETC1 compressed version of the data.
43
44void etc1_encode_block(const etc1_byte* pIn, etc1_uint32 validPixelMask, etc1_byte* pOut);
45
46// Decode a block of pixels.
47//
48// pIn is an ETC1 compressed version of the data.
49//
50// pOut is a pointer to a ETC_DECODED_BLOCK_SIZE array of bytes that represent a
51// 4 x 4 square of 3-byte pixels in form R, G, B. Byte (3 * (x + 4 * y) is the R
52// value of pixel (x, y).
53
54void etc1_decode_block(const etc1_byte* pIn, etc1_byte* pOut);
55
56// Return the size of the encoded image data (does not include size of PKM header).
57
58etc1_uint32 etc1_get_encoded_data_size(etc1_uint32 width, etc1_uint32 height);
59
60// Encode an entire image.
61// pIn - pointer to the image data. Formatted such that
62//       pixel (x,y) is at pIn + pixelSize * x + stride * y;
63// pOut - pointer to encoded data. Must be large enough to store entire encoded image.
64// pixelSize can be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 3 is a GL_BYTE RGB image.
65// returns non-zero if there is an error.
66
67int etc1_encode_image(const etc1_byte* pIn, etc1_uint32 width, etc1_uint32 height,
68        etc1_uint32 pixelSize, etc1_uint32 stride, etc1_byte* pOut);
69
70// Decode an entire image.
71// pIn - pointer to encoded data.
72// pOut - pointer to the image data. Will be written such that
73//        pixel (x,y) is at pIn + pixelSize * x + stride * y. Must be
74//        large enough to store entire image.
75// pixelSize can be 2 or 3. 2 is an GL_UNSIGNED_SHORT_5_6_5 image, 3 is a GL_BYTE RGB image.
76// returns non-zero if there is an error.
77
78int etc1_decode_image(const etc1_byte* pIn, etc1_byte* pOut,
79        etc1_uint32 width, etc1_uint32 height,
80        etc1_uint32 pixelSize, etc1_uint32 stride);
81
82// Size of a PKM header, in bytes.
83
84#define ETC_PKM_HEADER_SIZE 16
85
86// Format a PKM header
87
88void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height);
89
90// Check if a PKM header is correctly formatted.
91
92etc1_bool etc1_pkm_is_valid(const etc1_byte* pHeader);
93
94// Read the image width from a PKM header
95
96etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader);
97
98// Read the image height from a PKM header
99
100etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader);
101
102#ifdef __cplusplus
103}
104#endif
105
106#endif
107