mesa: add ETC1 decoding routines

The format is defined by GL_OES_compressed_ETC1_RGB8_texture.  These routines
will be used in the following commit.

Reviewed-by: Brian Paul <brianp@vmware.com>

1 files changed, 136 insertions, 0 deletions

diff --git a/src/mesa/main/texcompress_etc_tmp.h b/src/mesa/main/texcompress_etc_tmp.h
new file mode 100644
index 0000000..5c8c6de
--- /dev/null
+++ b/src/mesa/main/texcompress_etc_tmp.h
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2011 LunarG, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * Included by texcompress_etc1 and gallium to define ETC1 decoding routines.
+ */
+
+struct TAG(etc1_block) {
+   uint32_t pixel_indices;
+   int flipped;
+   const int *modifier_tables[2];
+   UINT8_TYPE base_colors[2][3];
+};
+
+static UINT8_TYPE
+TAG(etc1_base_color_diff_hi)(UINT8_TYPE in)
+{
+   return (in & 0xf8) | (in >> 5);
+}
+
+static UINT8_TYPE
+TAG(etc1_base_color_diff_lo)(UINT8_TYPE in)
+{
+   static const int lookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
+
+   in = (in >> 3) + lookup[in & 0x7];
+
+   return (in << 3) | (in >> 2);
+}
+
+static UINT8_TYPE
+TAG(etc1_base_color_ind_hi)(UINT8_TYPE in)
+{
+   return (in & 0xf0) | ((in & 0xf0) >> 4);
+}
+
+static UINT8_TYPE
+TAG(etc1_base_color_ind_lo)(UINT8_TYPE in)
+{
+   return ((in & 0xf) << 4) | (in & 0xf);
+}
+
+static UINT8_TYPE
+TAG(etc1_clamp)(UINT8_TYPE base, int modifier)
+{
+   int tmp = (int) base + modifier;
+
+   /* CLAMP(tmp, 0, 255) */
+   return (UINT8_TYPE) ((tmp < 0) ? 0 : ((tmp > 255) ? 255 : tmp));
+}
+
+static const int TAG(etc1_modifier_tables)[8][4] = {
+   {  2,   8,  -2,   -8},
+   {  5,  17,  -5,  -17},
+   {  9,  29,  -9,  -29},
+   { 13,  42, -13,  -42},
+   { 18,  60, -18,  -60},
+   { 24,  80, -24,  -80},
+   { 33, 106, -33, -106},
+   { 47, 183, -47, -183}
+};
+
+static void
+TAG(etc1_parse_block)(struct TAG(etc1_block) *block, const UINT8_TYPE *src)
+{
+   if (src[3] & 0x2) {
+      /* differential mode */
+      block->base_colors[0][0] = (int) TAG(etc1_base_color_diff_hi)(src[0]);
+      block->base_colors[1][0] = (int) TAG(etc1_base_color_diff_lo)(src[0]);
+      block->base_colors[0][1] = (int) TAG(etc1_base_color_diff_hi)(src[1]);
+      block->base_colors[1][1] = (int) TAG(etc1_base_color_diff_lo)(src[1]);
+      block->base_colors[0][2] = (int) TAG(etc1_base_color_diff_hi)(src[2]);
+      block->base_colors[1][2] = (int) TAG(etc1_base_color_diff_lo)(src[2]);
+   }
+   else {
+      /* individual mode */
+      block->base_colors[0][0] = (int) TAG(etc1_base_color_ind_hi)(src[0]);
+      block->base_colors[1][0] = (int) TAG(etc1_base_color_ind_lo)(src[0]);
+      block->base_colors[0][1] = (int) TAG(etc1_base_color_ind_hi)(src[1]);
+      block->base_colors[1][1] = (int) TAG(etc1_base_color_ind_lo)(src[1]);
+      block->base_colors[0][2] = (int) TAG(etc1_base_color_ind_hi)(src[2]);
+      block->base_colors[1][2] = (int) TAG(etc1_base_color_ind_lo)(src[2]);
+   }
+
+   /* pick modifier tables */
+   block->modifier_tables[0] = TAG(etc1_modifier_tables)[(src[3] >> 5) & 0x7];
+   block->modifier_tables[1] = TAG(etc1_modifier_tables)[(src[3] >> 2) & 0x7];
+
+   block->flipped = (src[3] & 0x1);
+
+   block->pixel_indices =
+      (src[4] << 24) | (src[5] << 16) | (src[6] << 8) | src[7];
+}
+
+static void
+TAG(etc1_fetch_texel)(const struct TAG(etc1_block) *block,
+      int x, int y, UINT8_TYPE *dst)
+{
+   const UINT8_TYPE *base_color;
+   int modifier, bit, idx, blk;
+
+   /* get pixel index */
+   bit = y + x * 4;
+   idx = ((block->pixel_indices >> (15 + bit)) & 0x2) |
+         ((block->pixel_indices >>      (bit)) & 0x1);
+
+   /* get subblock */
+   blk = (block->flipped) ? (y >= 2) : (x >= 2);
+
+   base_color = block->base_colors[blk];
+   modifier = block->modifier_tables[blk][idx];
+
+   dst[0] = TAG(etc1_clamp)(base_color[0], modifier);
+   dst[1] = TAG(etc1_clamp)(base_color[1], modifier);
+   dst[2] = TAG(etc1_clamp)(base_color[2], modifier);
+}