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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 
25 typedef unsigned char etc1_byte;
26 typedef int etc1_bool;
27 typedef unsigned int etc1_uint32;
28 
29 #ifdef __cplusplus
30 extern "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 
44 void 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 
54 void 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 
58 etc1_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 
67 int 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 
78 int 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 
88 void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height);
89 
90 // Check if a PKM header is correctly formatted.
91 
92 etc1_bool etc1_pkm_is_valid(const etc1_byte* pHeader);
93 
94 // Read the image width from a PKM header
95 
96 etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader);
97 
98 // Read the image height from a PKM header
99 
100 etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader);
101 
102 #ifdef __cplusplus
103 }
104 #endif
105 
106 #endif
107