1/*
2 * Copyright (C) 2011 LunarG, Inc.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24/*
25 * Included by texcompress_etc1 and gallium to define ETC1 decoding routines.
26 */
27
28struct TAG(etc1_block) {
29   uint32_t pixel_indices;
30   int flipped;
31   const int *modifier_tables[2];
32   UINT8_TYPE base_colors[2][3];
33};
34
35static UINT8_TYPE
36TAG(etc1_base_color_diff_hi)(UINT8_TYPE in)
37{
38   return (in & 0xf8) | (in >> 5);
39}
40
41static UINT8_TYPE
42TAG(etc1_base_color_diff_lo)(UINT8_TYPE in)
43{
44   static const int lookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
45
46   in = (in >> 3) + lookup[in & 0x7];
47
48   return (in << 3) | (in >> 2);
49}
50
51static UINT8_TYPE
52TAG(etc1_base_color_ind_hi)(UINT8_TYPE in)
53{
54   return (in & 0xf0) | ((in & 0xf0) >> 4);
55}
56
57static UINT8_TYPE
58TAG(etc1_base_color_ind_lo)(UINT8_TYPE in)
59{
60   return ((in & 0xf) << 4) | (in & 0xf);
61}
62
63static UINT8_TYPE
64TAG(etc1_clamp)(UINT8_TYPE base, int modifier)
65{
66   int tmp = (int) base + modifier;
67
68   /* CLAMP(tmp, 0, 255) */
69   return (UINT8_TYPE) ((tmp < 0) ? 0 : ((tmp > 255) ? 255 : tmp));
70}
71
72static const int TAG(etc1_modifier_tables)[8][4] = {
73   {  2,   8,  -2,   -8},
74   {  5,  17,  -5,  -17},
75   {  9,  29,  -9,  -29},
76   { 13,  42, -13,  -42},
77   { 18,  60, -18,  -60},
78   { 24,  80, -24,  -80},
79   { 33, 106, -33, -106},
80   { 47, 183, -47, -183}
81};
82
83static void
84TAG(etc1_parse_block)(struct TAG(etc1_block) *block, const UINT8_TYPE *src)
85{
86   if (src[3] & 0x2) {
87      /* differential mode */
88      block->base_colors[0][0] = (int) TAG(etc1_base_color_diff_hi)(src[0]);
89      block->base_colors[1][0] = (int) TAG(etc1_base_color_diff_lo)(src[0]);
90      block->base_colors[0][1] = (int) TAG(etc1_base_color_diff_hi)(src[1]);
91      block->base_colors[1][1] = (int) TAG(etc1_base_color_diff_lo)(src[1]);
92      block->base_colors[0][2] = (int) TAG(etc1_base_color_diff_hi)(src[2]);
93      block->base_colors[1][2] = (int) TAG(etc1_base_color_diff_lo)(src[2]);
94   }
95   else {
96      /* individual mode */
97      block->base_colors[0][0] = (int) TAG(etc1_base_color_ind_hi)(src[0]);
98      block->base_colors[1][0] = (int) TAG(etc1_base_color_ind_lo)(src[0]);
99      block->base_colors[0][1] = (int) TAG(etc1_base_color_ind_hi)(src[1]);
100      block->base_colors[1][1] = (int) TAG(etc1_base_color_ind_lo)(src[1]);
101      block->base_colors[0][2] = (int) TAG(etc1_base_color_ind_hi)(src[2]);
102      block->base_colors[1][2] = (int) TAG(etc1_base_color_ind_lo)(src[2]);
103   }
104
105   /* pick modifier tables */
106   block->modifier_tables[0] = TAG(etc1_modifier_tables)[(src[3] >> 5) & 0x7];
107   block->modifier_tables[1] = TAG(etc1_modifier_tables)[(src[3] >> 2) & 0x7];
108
109   block->flipped = (src[3] & 0x1);
110
111   block->pixel_indices =
112      (src[4] << 24) | (src[5] << 16) | (src[6] << 8) | src[7];
113}
114
115static void
116TAG(etc1_fetch_texel)(const struct TAG(etc1_block) *block,
117      int x, int y, UINT8_TYPE *dst)
118{
119   const UINT8_TYPE *base_color;
120   int modifier, bit, idx, blk;
121
122   /* get pixel index */
123   bit = y + x * 4;
124   idx = ((block->pixel_indices >> (15 + bit)) & 0x2) |
125         ((block->pixel_indices >>      (bit)) & 0x1);
126
127   /* get subblock */
128   blk = (block->flipped) ? (y >= 2) : (x >= 2);
129
130   base_color = block->base_colors[blk];
131   modifier = block->modifier_tables[blk][idx];
132
133   dst[0] = TAG(etc1_clamp)(base_color[0], modifier);
134   dst[1] = TAG(etc1_clamp)(base_color[1], modifier);
135   dst[2] = TAG(etc1_clamp)(base_color[2], modifier);
136}
137
138static void
139etc1_unpack_rgba8888(uint8_t *dst_row,
140                     unsigned dst_stride,
141                     const uint8_t *src_row,
142                     unsigned src_stride,
143                     unsigned width,
144                     unsigned height)
145{
146   const unsigned bw = 4, bh = 4, bs = 8, comps = 4;
147   struct etc1_block block;
148   unsigned x, y, i, j;
149
150   for (y = 0; y < height; y += bh) {
151      const uint8_t *src = src_row;
152
153      for (x = 0; x < width; x+= bw) {
154         etc1_parse_block(&block, src);
155
156         for (j = 0; j < bh; j++) {
157            uint8_t *dst = dst_row + (y + j) * dst_stride + x * comps;
158            for (i = 0; i < bw; i++) {
159               etc1_fetch_texel(&block, i, j, dst);
160               dst[3] = 255;
161               dst += comps;
162            }
163         }
164
165         src += bs;
166      }
167
168      src_row += src_stride;
169   }
170}
171