mesa: Add decoding functions for GL_COMPRESSED_RGB8_ETC2

Data in GL_COMPRESSED_RGB8_ETC2 format is decoded and stored in
MESA_FORMAT_RGBX8888_REV.

v2: Use CLAMP macro and stdbool.h
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/texcompress.c

@@ -608,7 +608,7 @@ _mesa_decompress_image(gl_format format, GLuint width, GLuint height,
 
    /* ETC2 formats */
    case MESA_FORMAT_ETC2_RGB8:
-      /* fetch = _mesa_fetch_texel_2d_f_etc2_rgb8; -- not implemented yet */
+      fetch = _mesa_fetch_texel_2d_f_etc2_rgb8;
       break;
    case MESA_FORMAT_ETC2_SRGB8:
       /* fetch = _mesa_fetch_texel_2d_f_etc2_srgb8; -- not implemented yet */

src/mesa/main/texcompress_etc.c

@@ -24,9 +24,11 @@
 /**
  * \file texcompress_etc.c
  * GL_OES_compressed_ETC1_RGB8_texture support.
+ * Supported ETC2 texture formats are:
+ * GL_COMPRESSED_RGB8_ETC2
  */
 
-
+#include <stdbool.h>
 #include "mfeatures.h"
 #include "texcompress.h"
 #include "texcompress_etc.h"
@@ -34,6 +36,30 @@
 #include "macros.h"
 #include "swrast/s_context.h"
 
+struct etc2_block {
+   int distance;
+   uint32_t pixel_indices;
+   const int *modifier_tables[2];
+   bool flipped;
+   bool is_ind_mode;
+   bool is_diff_mode;
+   bool is_t_mode;
+   bool is_h_mode;
+   bool is_planar_mode;
+   uint8_t base_colors[3][3];
+   uint8_t paint_colors[4][3];
+};
+
+static const int etc2_distance_table[8] = {
+   3, 6, 11, 16, 23, 32, 41, 64 };
+
+/* define etc1_parse_block and etc. */
+#define UINT8_TYPE GLubyte
+#define TAG(x) x
+#include "texcompress_etc_tmp.h"
+#undef TAG
+#undef UINT8_TYPE
+
 GLboolean
 _mesa_texstore_etc1_rgb8(TEXSTORE_PARAMS)
 {
@@ -43,13 +69,6 @@ _mesa_texstore_etc1_rgb8(TEXSTORE_PARAMS)
    return GL_FALSE;
 }
 
-/* define etc1_parse_block and etc. */
-#define UINT8_TYPE GLubyte
-#define TAG(x) x
-#include "texcompress_etc_tmp.h"
-#undef TAG
-#undef UINT8_TYPE
-
 void
 _mesa_fetch_texel_2d_f_etc1_rgb8(const struct swrast_texture_image *texImage,
                                  GLint i, GLint j, GLint k, GLfloat *texel)
@@ -101,3 +120,428 @@ _mesa_etc1_unpack_rgba8888(uint8_t *dst_row,
                         src_row, src_stride,
                         src_width, src_height);
 }
+
+static uint8_t
+etc2_base_color1_t_mode(const uint8_t *in, GLuint index)
+{
+   uint8_t R1a = 0, x = 0;
+   /* base col 1 = extend_4to8bits( (R1a << 2) | R1b, G1, B1) */
+   switch(index) {
+   case 0:
+      R1a = (in[0] >> 3) & 0x3;
+      x = ((R1a << 2) | (in[0] & 0x3));
+      break;
+   case 1:
+      x = ((in[1] >> 4) & 0xf);
+      break;
+   case 2:
+      x = (in[1] & 0xf);
+      break;
+   default:
+      /* invalid index */
+      break;
+   }
+   return ((x << 4) | (x & 0xf));
+}
+
+static uint8_t
+etc2_base_color2_t_mode(const uint8_t *in, GLuint index)
+{
+   uint8_t x = 0;
+   /*extend 4to8bits(R2, G2, B2)*/
+   switch(index) {
+   case 0:
+      x = ((in[2] >> 4) & 0xf );
+      break;
+   case 1:
+      x = (in[2] & 0xf);
+      break;
+   case 2:
+      x = ((in[3] >> 4) & 0xf);
+      break;
+   default:
+      /* invalid index */
+      break;
+   }
+   return ((x << 4) | (x & 0xf));
+}
+
+static uint8_t
+etc2_base_color1_h_mode(const uint8_t *in, GLuint index)
+{
+   uint8_t x = 0;
+   /* base col 1 = extend 4to8bits(R1, (G1a << 1) | G1b, (B1a << 3) | B1b) */
+   switch(index) {
+   case 0:
+      x = ((in[0] >> 3) & 0xf);
+      break;
+   case 1:
+      x = (((in[0] & 0x7) << 1) | ((in[1] >> 4) & 0x1));
+      break;
+   case 2:
+      x = ((in[1] & 0x8) |
+           (((in[1] & 0x3) << 1) | ((in[2] >> 7) & 0x1)));
+      break;
+   default:
+      /* invalid index */
+      break;
+   }
+   return ((x << 4) | (x & 0xf));
+ }
+
+static uint8_t
+etc2_base_color2_h_mode(const uint8_t *in, GLuint index)
+{
+   uint8_t x = 0;
+   /* base col 2 = extend 4to8bits(R2, G2, B2) */
+   switch(index) {
+   case 0:
+      x = ((in[2] >> 3) & 0xf );
+      break;
+   case 1:
+      x = (((in[2] & 0x7) << 1) | ((in[3] >> 7) & 0x1));
+      break;
+   case 2:
+      x = ((in[3] >> 3) & 0xf);
+      break;
+   default:
+      /* invalid index */
+      break;
+   }
+   return ((x << 4) | (x & 0xf));
+ }
+
+static uint8_t
+etc2_base_color_o_planar(const uint8_t *in, GLuint index)
+{
+   GLuint tmp;
+   switch(index) {
+   case 0:
+      tmp = ((in[0] >> 1) & 0x3f); /* RO */
+      return ((tmp << 2) | (tmp >> 4));
+   case 1:
+      tmp = (((in[0] & 0x1) << 6) | /* GO1 */
+             ((in[1] >> 1) & 0x3f)); /* GO2 */
+      return ((tmp << 1) | (tmp >> 6));
+   case 2:
+      tmp = (((in[1] & 0x1) << 5) | /* BO1 */
+             (in[2] & 0x18) | /* BO2 */
+             (((in[2] & 0x3) << 1) | ((in[3] >> 7) & 0x1))); /* BO3 */
+      return ((tmp << 2) | (tmp >> 4));
+    default:
+      /* invalid index */
+      return 0;
+   }
+}
+
+static uint8_t
+etc2_base_color_h_planar(const uint8_t *in, GLuint index)
+{
+   GLuint tmp;
+   switch(index) {
+   case 0:
+      tmp = (((in[3] & 0x7c) >> 1) | /* RH1 */
+             (in[3] & 0x1));         /* RH2 */
+      return ((tmp << 2) | (tmp >> 4));
+   case 1:
+      tmp = (in[4] >> 1) & 0x7f; /* GH */
+      return ((tmp << 1) | (tmp >> 6));
+   case 2:
+      tmp = (((in[4] & 0x1) << 5) |
+             ((in[5] >> 3) & 0x1f)); /* BH */
+      return ((tmp << 2) | (tmp >> 4));
+   default:
+      /* invalid index */
+      return 0;
+   }
+}
+
+static uint8_t
+etc2_base_color_v_planar(const uint8_t *in, GLuint index)
+{
+   GLuint tmp;
+   switch(index) {
+   case 0:
+      tmp = (((in[5] & 0x7) << 0x3) |
+             ((in[6] >> 5) & 0x7)); /* RV */
+      return ((tmp << 2) | (tmp >> 4));
+   case 1:
+      tmp = (((in[6] & 0x1f) << 2) |
+             ((in[7] >> 6) & 0x3)); /* GV */
+      return ((tmp << 1) | (tmp >> 6));
+   case 2:
+      tmp = in[7] & 0x3f; /* BV */
+      return ((tmp << 2) | (tmp >> 4));
+   default:
+      /* invalid index */
+      return 0;
+   }
+}
+
+static uint8_t
+etc2_clamp(int color)
+{
+   /* CLAMP(color, 0, 255) */
+   return (uint8_t) CLAMP(color, 0, 255);
+}
+
+static void
+etc2_rgb8_parse_block(struct etc2_block *block, const uint8_t *src)
+{
+   unsigned i;
+   GLboolean diffbit = src[3] & 0x2;
+   static const int lookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
+
+   const int R_plus_dR = (src[0] >> 3) + lookup[src[0] & 0x7];
+   const int G_plus_dG = (src[1] >> 3) + lookup[src[1] & 0x7];
+   const int B_plus_dB = (src[2] >> 3) + lookup[src[2] & 0x7];
+
+   /* Reset the mode flags */
+   block->is_ind_mode = false;
+   block->is_diff_mode = false;
+   block->is_t_mode = false;
+   block->is_h_mode = false;
+   block->is_planar_mode = false;
+
+   if (!diffbit) {
+      /* individual mode */
+      block->is_ind_mode = true;
+
+      for (i = 0; i < 3; i++) {
+         /* Texture decode algorithm is same for individual mode in etc1
+          * & etc2.
+          */
+         block->base_colors[0][i] = etc1_base_color_ind_hi(src[i]);
+         block->base_colors[1][i] = etc1_base_color_ind_lo(src[i]);
+      }
+   }
+   else if (R_plus_dR < 0 || R_plus_dR > 31){
+      /* T mode */
+      block->is_t_mode = true;
+
+      for(i = 0; i < 3; i++) {
+         block->base_colors[0][i] = etc2_base_color1_t_mode(src, i);
+         block->base_colors[1][i] = etc2_base_color2_t_mode(src, i);
+      }
+      /* pick distance */
+      block->distance =
+         etc2_distance_table[(((src[3] >> 2) & 0x3) << 1) |
+                             (src[3] & 0x1)];
+
+      for (i = 0; i < 3; i++) {
+         block->paint_colors[0][i] = etc2_clamp(block->base_colors[0][i]);
+         block->paint_colors[1][i] = etc2_clamp(block->base_colors[1][i] +
+                                                block->distance);
+         block->paint_colors[2][i] = etc2_clamp(block->base_colors[1][i]);
+         block->paint_colors[3][i] = etc2_clamp(block->base_colors[1][i] -
+                                                block->distance);
+      }
+   }
+   else if (G_plus_dG < 0 || G_plus_dG > 31){
+      /* H mode */
+      block->is_h_mode = true;
+      int base_color_1_value, base_color_2_value;
+
+      for(i = 0; i < 3; i++) {
+         block->base_colors[0][i] = etc2_base_color1_h_mode(src, i);
+         block->base_colors[1][i] = etc2_base_color2_h_mode(src, i);
+      }
+
+      base_color_1_value = (block->base_colors[0][0] << 16) +
+                           (block->base_colors[0][1] << 8) +
+                           block->base_colors[0][2];
+      base_color_2_value = (block->base_colors[1][0] << 16) +
+                           (block->base_colors[1][1] << 8) +
+                           block->base_colors[1][2];
+      /* pick distance */
+      block->distance =
+         etc2_distance_table[(src[3] & 0x4) |
+                             ((src[3] & 0x1) << 1) |
+                             (base_color_1_value >= base_color_2_value)];
+
+      for (i = 0; i < 3; i++) {
+         block->paint_colors[0][i] = etc2_clamp(block->base_colors[0][i] +
+                                                block->distance);
+         block->paint_colors[1][i] = etc2_clamp(block->base_colors[0][i] -
+                                                block->distance);
+         block->paint_colors[2][i] = etc2_clamp(block->base_colors[1][i] +
+                                                block->distance);
+         block->paint_colors[3][i] = etc2_clamp(block->base_colors[1][i] -
+                                                block->distance);
+      }
+   }
+   else if (B_plus_dB < 0 || B_plus_dB > 31){
+      /* Planar mode */
+      block->is_planar_mode = true;
+
+      for (i = 0; i < 3; i++) {
+         block->base_colors[0][i] = etc2_base_color_o_planar(src, i);
+         block->base_colors[1][i] = etc2_base_color_h_planar(src, i);
+         block->base_colors[2][i] = etc2_base_color_v_planar(src, i);
+      }
+   }
+   else if (diffbit) {
+      /* differential mode */
+      block->is_diff_mode = true;
+
+      for (i = 0; i < 3; i++) {
+         /* Texture decode algorithm is same for differential mode in etc1
+          * & etc2.
+          */
+         block->base_colors[0][i] = etc1_base_color_diff_hi(src[i]);
+         block->base_colors[1][i] = etc1_base_color_diff_lo(src[i]);
+     }
+   }
+
+   if (block->is_ind_mode || block->is_diff_mode) {
+      /* pick modifier tables. same for etc1 & etc2 textures */
+      block->modifier_tables[0] = etc1_modifier_tables[(src[3] >> 5) & 0x7];
+      block->modifier_tables[1] = 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
+etc2_rgb8_fetch_texel(const struct etc2_block *block,
+      int x, int y, uint8_t *dst)
+{
+   const uint8_t *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);
+
+   if (block->is_ind_mode || block->is_diff_mode) {
+      /* Use pixel index and subblock to get the modifier */
+      blk = (block->flipped) ? (y >= 2) : (x >= 2);
+      base_color = block->base_colors[blk];
+      modifier = block->modifier_tables[blk][idx];
+
+      dst[0] = etc2_clamp(base_color[0] + modifier);
+      dst[1] = etc2_clamp(base_color[1] + modifier);
+      dst[2] = etc2_clamp(base_color[2] + modifier);
+   }
+   else if (block->is_t_mode || block->is_h_mode) {
+      /* Use pixel index to pick one of the paint colors */
+      dst[0] = block->paint_colors[idx][0];
+      dst[1] = block->paint_colors[idx][1];
+      dst[2] = block->paint_colors[idx][2];
+   }
+   else if (block->is_planar_mode) {
+      /* {R(x, y) = clamp255((x × (RH − RO) + y × (RV − RO) + 4 × RO + 2) >> 2)
+       * {G(x, y) = clamp255((x × (GH − GO) + y × (GV − GO) + 4 × GO + 2) >> 2)
+       * {B(x, y) = clamp255((x × (BH − BO) + y × (BV − BO) + 4 × BO + 2) >> 2)
+       */
+      int red, green, blue;
+      red = (x * (block->base_colors[1][0] - block->base_colors[0][0]) +
+             y * (block->base_colors[2][0] - block->base_colors[0][0]) +
+             4 * block->base_colors[0][0] + 2) >> 2;
+
+      green = (x * (block->base_colors[1][1] - block->base_colors[0][1]) +
+               y * (block->base_colors[2][1] - block->base_colors[0][1]) +
+               4 * block->base_colors[0][1] + 2) >> 2;
+
+      blue = (x * (block->base_colors[1][2] - block->base_colors[0][2]) +
+              y * (block->base_colors[2][2] - block->base_colors[0][2]) +
+              4 * block->base_colors[0][2] + 2) >> 2;
+
+      dst[0] = etc2_clamp(red);
+      dst[1] = etc2_clamp(green);
+      dst[2] = etc2_clamp(blue);
+  }
+}
+
+static void
+etc2_unpack_rgb8(uint8_t *dst_row,
+                 unsigned dst_stride,
+                 const uint8_t *src_row,
+                 unsigned src_stride,
+                 unsigned width,
+                 unsigned height)
+{
+   const unsigned bw = 4, bh = 4, bs = 8, comps = 4;
+   struct etc2_block block;
+   unsigned x, y, i, j;
+
+   for (y = 0; y < height; y += bh) {
+      const uint8_t *src = src_row;
+
+      for (x = 0; x < width; x+= bw) {
+         etc2_rgb8_parse_block(&block, src);
+
+         for (j = 0; j < bh; j++) {
+            uint8_t *dst = dst_row + (y + j) * dst_stride + x * comps;
+            for (i = 0; i < bw; i++) {
+               etc2_rgb8_fetch_texel(&block, i, j, dst);
+               dst[3] = 255;
+               dst += comps;
+            }
+         }
+
+         src += bs;
+      }
+
+      src_row += src_stride;
+   }
+}
+
+/* ETC2 texture formats are valid in glCompressedTexImage2D and
+ * glCompressedTexSubImage2D functions */
+GLboolean
+_mesa_texstore_etc2_rgb8(TEXSTORE_PARAMS)
+{
+   ASSERT(0);
+
+   return GL_FALSE;
+}
+
+void
+_mesa_fetch_texel_2d_f_etc2_rgb8(const struct swrast_texture_image *texImage,
+                                 GLint i, GLint j, GLint k, GLfloat *texel)
+{
+   struct etc2_block block;
+   uint8_t dst[3];
+   const uint8_t *src;
+
+   src = texImage->Map +
+      (((texImage->RowStride + 3) / 4) * (j / 4) + (i / 4)) * 8;
+
+   etc2_rgb8_parse_block(&block, src);
+   etc2_rgb8_fetch_texel(&block, i % 4, j % 4, dst);
+
+   texel[RCOMP] = UBYTE_TO_FLOAT(dst[0]);
+   texel[GCOMP] = UBYTE_TO_FLOAT(dst[1]);
+   texel[BCOMP] = UBYTE_TO_FLOAT(dst[2]);
+   texel[ACOMP] = 1.0f;
+}
+
+
+/**
+ * Decode texture data in format `MESA_FORMAT_ETC2_RGB8`
+ *
+ * The size of the source data must be a multiple of the ETC2 block size
+ * even if the texture image's dimensions are not aligned to 4.
+ *
+ * \param src_width in pixels
+ * \param src_height in pixels
+ * \param dst_stride in bytes
+ */
+
+void
+_mesa_unpack_etc2_format(uint8_t *dst_row,
+                         unsigned dst_stride,
+                         const uint8_t *src_row,
+                         unsigned src_stride,
+                         unsigned src_width,
+                         unsigned src_height,
+                         gl_format format)
+{
+   etc2_unpack_rgb8(dst_row, dst_stride,
+                    src_row, src_stride,
+                    src_width, src_height);
+}

src/mesa/main/texcompress_etc.h

@@ -34,10 +34,15 @@ struct swrast_texture_image;
 GLboolean
 _mesa_texstore_etc1_rgb8(TEXSTORE_PARAMS);
 
+GLboolean
+_mesa_texstore_etc2_rgb8(TEXSTORE_PARAMS);
+
 void
 _mesa_fetch_texel_2d_f_etc1_rgb8(const struct swrast_texture_image *texImage,
                                  GLint i, GLint j, GLint k, GLfloat *texel);
-
+void
+_mesa_fetch_texel_2d_f_etc2_rgb8(const struct swrast_texture_image *texImage,
+                                 GLint i, GLint j, GLint k, GLfloat *texel);
 void
 _mesa_etc1_unpack_rgba8888(uint8_t *dst_row,
                            unsigned dst_stride,
@@ -45,5 +50,12 @@ _mesa_etc1_unpack_rgba8888(uint8_t *dst_row,
                            unsigned src_stride,
                            unsigned src_width,
                            unsigned src_height);
-
+void
+_mesa_unpack_etc2_format(uint8_t *dst_row,
+                         unsigned dst_stride,
+                         const uint8_t *src_row,
+                         unsigned src_stride,
+                         unsigned src_width,
+                         unsigned src_height,
+                         gl_format format);
 #endif

src/mesa/main/texstore.c

@@ -4124,7 +4124,7 @@ _mesa_get_texstore_func(gl_format format)
       table[MESA_FORMAT_LA_LATC2] = _mesa_texstore_rg_rgtc2;
       table[MESA_FORMAT_SIGNED_LA_LATC2] = _mesa_texstore_signed_rg_rgtc2;
       table[MESA_FORMAT_ETC1_RGB8] = _mesa_texstore_etc1_rgb8;
-      /* table[MESA_FORMAT_ETC2_RGB8] = _mesa_texstore_etc2_rgb8; -- not implemented yet */
+      table[MESA_FORMAT_ETC2_RGB8] = _mesa_texstore_etc2_rgb8;
       /* table[MESA_FORMAT_ETC2_SRGB8] = _mesa_texstore_etc2_srgb8; -- not implemented yet */
       /* table[MESA_FORMAT_ETC2_RGBA8_EAC] = _mesa_texstore_etc2_rgba8_eac; -- not implemented yet */
       /* table[MESA_FORMAT_ETC2_SRGB8_ALPHA8_EAC] = _mesa_texstore_etc2_srgb8_alpha8_eac; -- not implemented yet */

src/mesa/swrast/s_texfetch.c

@@ -1031,7 +1031,7 @@ texfetch_funcs[] =
    {
       MESA_FORMAT_ETC2_RGB8,
       NULL,
-      NULL /* _mesa_fetch_texel_2d_f_etc2_rgb8 -- not implemented yet */,
+      _mesa_fetch_texel_2d_f_etc2_rgb8,
       NULL
    },
    {