mesa: Add decoding functions for GL_COMPRESSED_SIGNED_R11_EAC

Data in GL_COMPRESSED_SIGNED_R11_EAC format is decoded and stored in
MESA_FORMAT_SIGNED_R16.

v2:
16 bit signed data is converted to 16 bit unsigned data by
adding 2 ^ 15 and stored in an unsigned texture format.

v3:
1. Handle a corner case when base code word value is -128. As per
OpenGL ES 3.0 specification -128 is not an allowed value and should
be truncated to -127.
2. Converting a decoded 16 bit signed data to 16 bit unsigned data by
adding 2 ^ 15 gives us an output which matches the decompressed image
(.ppm) generated by ericsson's etcpack tool. ericsson is also doing this
conversion in their tool because .ppm image files don't support signed
data. But gles 3.0 specification doesn't suggest this conversion. We
need to keep the decoded data in signed format. Both signed format
tests in gles3 conformance pass with these changes.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Tested-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/texcompress.c

@@ -626,7 +626,7 @@ _mesa_decompress_image(gl_format format, GLuint width, GLuint height,
       fetch = _mesa_fetch_texel_2d_f_etc2_rg11_eac;
       break;
    case MESA_FORMAT_ETC2_SIGNED_R11_EAC:
-      /* fetch = _mesa_fetch_texel_2d_f_etc2_signed_r11_eac; -- not implemented yet */
+      fetch = _mesa_fetch_texel_2d_f_etc2_signed_r11_eac;
       break;
    case MESA_FORMAT_ETC2_SIGNED_RG11_EAC:
       /* fetch = _mesa_fetch_texel_2d_f_etc2_signed_rg11_eac; -- not implemented yet */

src/mesa/main/texcompress_etc.c

@@ -31,6 +31,7 @@
  * GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC
  * GL_COMPRESSED_R11_EAC
  * GL_COMPRESSED_RG11_EAC
+ * GL_COMPRESSED_SIGNED_R11_EAC
  */
 
 #include <stdbool.h>
@@ -328,6 +329,13 @@ etc2_clamp2(int color)
    return (GLushort) CLAMP(color, 0, 2047);
 }
 
+static GLshort
+etc2_clamp3(int color)
+{
+   /* CLAMP(color, -1023, 1023) */
+   return (GLshort) CLAMP(color, -1023, 1023);
+}
+
 static void
 etc2_rgb8_parse_block(struct etc2_block *block, const uint8_t *src)
 {
@@ -537,6 +545,44 @@ etc2_r11_fetch_texel(const struct etc2_block *block,
    ((GLushort *)dst)[0] = color;
 }
 
+static void
+etc2_signed_r11_fetch_texel(const struct etc2_block *block,
+                            int x, int y, uint8_t *dst)
+{
+   GLint modifier, idx;
+   GLshort color;
+   GLbyte base_codeword = (GLbyte) block->base_codeword;
+
+   if (base_codeword == -128)
+      base_codeword = -127;
+
+   /* Get pixel index */
+   idx = etc2_get_pixel_index(block, x, y);
+   modifier = etc2_modifier_tables[block->table_index][idx];
+
+   if (block->multiplier != 0)
+      /* clamp3(base codeword × 8 + modifier × multiplier × 8) */
+      color = etc2_clamp3((base_codeword << 3)  +
+                         ((modifier * block->multiplier) << 3));
+   else
+      color = etc2_clamp3((base_codeword << 3)  + modifier);
+
+   /* Extend 11 bits color value to 16 bits. OpenGL ES 3.0 specification
+    * allows extending the color value to any number of bits. But, an
+    * implementation is not allowed to truncate the 11-bit value to less than
+    * 11 bits. A negative 11-bit value must first be made positive before bit
+    * replication, and then made negative again
+    */
+   if (color >= 0)
+      color = (color << 5) | (color >> 5);
+   else {
+      color = -color;
+      color = (color << 5) | (color >> 5);
+      color = -color;
+   }
+   ((GLshort *)dst)[0] = color;
+}
+
 static void
 etc2_alpha8_parse_block(struct etc2_block *block, const uint8_t *src)
 {
@@ -812,6 +858,42 @@ etc2_unpack_rg11(uint8_t *dst_row,
     }
 }
 
+static void
+etc2_unpack_signed_r11(uint8_t *dst_row,
+                       unsigned dst_stride,
+                       const uint8_t *src_row,
+                       unsigned src_stride,
+                       unsigned width,
+                       unsigned height)
+{
+   /* If internalformat is COMPRESSED_SIGNED_R11_EAC, each 4 × 4 block of
+      red color information is compressed to 64 bits.
+   */
+   const unsigned bw = 4, bh = 4, bs = 8, comps = 1, comp_size = 2;
+   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_r11_parse_block(&block, src);
+
+         for (j = 0; j < bh; j++) {
+            uint8_t *dst = dst_row + (y + j) * dst_stride +
+                           x * comps * comp_size;
+            for (i = 0; i < bw; i++) {
+               etc2_signed_r11_fetch_texel(&block, i, j, dst);
+               dst += comps * comp_size;
+            }
+         }
+         src += bs;
+       }
+
+      src_row += src_stride;
+    }
+}
+
 /* ETC2 texture formats are valid in glCompressedTexImage2D and
  * glCompressedTexSubImage2D functions */
 GLboolean
@@ -854,6 +936,14 @@ _mesa_texstore_etc2_r11_eac(TEXSTORE_PARAMS)
    return GL_FALSE;
 }
 
+GLboolean
+_mesa_texstore_etc2_signed_r11_eac(TEXSTORE_PARAMS)
+{
+   ASSERT(0);
+
+   return GL_FALSE;
+}
+
 GLboolean
 _mesa_texstore_etc2_rg11_eac(TEXSTORE_PARAMS)
 {
@@ -991,6 +1081,26 @@ _mesa_fetch_texel_2d_f_etc2_rg11_eac(const struct
    texel[ACOMP] = 1.0f;
 }
 
+void
+_mesa_fetch_texel_2d_f_etc2_signed_r11_eac(const struct swrast_texture_image *texImage,
+                                           GLint i, GLint j, GLint k, GLfloat *texel)
+{
+   struct etc2_block block;
+   GLushort dst;
+   const uint8_t *src;
+
+   src = texImage->Map +
+      (((texImage->RowStride + 3) / 4) * (j / 4) + (i / 4)) * 8;
+
+   etc2_r11_parse_block(&block, src);
+   etc2_signed_r11_fetch_texel(&block, i % 4, j % 4, (uint8_t *)&dst);
+
+   texel[RCOMP] = SHORT_TO_FLOAT(dst);
+   texel[GCOMP] = 0.0f;
+   texel[BCOMP] = 0.0f;
+   texel[ACOMP] = 1.0f;
+}
+
 /**
  * Decode texture data in any one of following formats:
  * `MESA_FORMAT_ETC2_RGB8`
@@ -999,6 +1109,7 @@ _mesa_fetch_texel_2d_f_etc2_rg11_eac(const struct
  * `MESA_FORMAT_ETC2_SRGB8_ALPHA8_EAC`
  * `MESA_FORMAT_ETC2_R11_EAC`
  * `MESA_FORMAT_ETC2_RG11_EAC`
+ * `MESA_FORMAT_ETC2_SIGNED_R11_EAC`
  *
  * 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.
@@ -1041,4 +1152,8 @@ _mesa_unpack_etc2_format(uint8_t *dst_row,
       etc2_unpack_rg11(dst_row, dst_stride,
                        src_row, src_stride,
                        src_width, src_height);
+   else if (format == MESA_FORMAT_ETC2_SIGNED_R11_EAC)
+      etc2_unpack_signed_r11(dst_row, dst_stride,
+                             src_row, src_stride,
+                             src_width, src_height);
 }

src/mesa/main/texcompress_etc.h

@@ -52,6 +52,9 @@ _mesa_texstore_etc2_r11_eac(TEXSTORE_PARAMS);
 GLboolean
 _mesa_texstore_etc2_rg11_eac(TEXSTORE_PARAMS);
 
+GLboolean
+_mesa_texstore_etc2_signed_r11_eac(TEXSTORE_PARAMS);
+
 void
 _mesa_fetch_texel_2d_f_etc1_rgb8(const struct swrast_texture_image *texImage,
                                  GLint i, GLint j, GLint k, GLfloat *texel);
@@ -77,6 +80,11 @@ void
 _mesa_fetch_texel_2d_f_etc2_rg11_eac(const struct swrast_texture_image *texImage,
                                      GLint i, GLint j, GLint k, GLfloat *texel);
 void
+_mesa_fetch_texel_2d_f_etc2_signed_r11_eac(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,
                            const uint8_t *src_row,

src/mesa/main/texstore.c

@@ -4130,7 +4130,7 @@ _mesa_get_texstore_func(gl_format format)
       table[MESA_FORMAT_ETC2_SRGB8_ALPHA8_EAC] = _mesa_texstore_etc2_srgb8_alpha8_eac;
       table[MESA_FORMAT_ETC2_R11_EAC] = _mesa_texstore_etc2_r11_eac;
       table[MESA_FORMAT_ETC2_RG11_EAC] = _mesa_texstore_etc2_rg11_eac;
-      /* table[MESA_FORMAT_ETC2_SIGNED_R11_EAC] = _mesa_texstore_etc2_signed_r11_eac; -- not implemented yet */
+      table[MESA_FORMAT_ETC2_SIGNED_R11_EAC] = _mesa_texstore_etc2_signed_r11_eac;
       /* table[MESA_FORMAT_ETC2_SIGNED_RG11_EAC] = _mesa_texstore_etc2_signed_rg11_eac; -- not implemented yet */
       /* table[MESA_FORMAT_ETC2_RGB8_PUNCHTHROUGH_ALPHA1] =
          _mesa_texstore_etc2_rgb8_punchthrough_alpha1; -- not implemented yet */

src/mesa/swrast/s_texfetch.c

@@ -1067,7 +1067,7 @@ texfetch_funcs[] =
    {
       MESA_FORMAT_ETC2_SIGNED_R11_EAC,
       NULL,
-      NULL /* _mesa_fetch_texel_2d_f_etc2_signed_r11_eac -- not implemented yet */,
+      _mesa_fetch_texel_2d_f_etc2_signed_r11_eac,
       NULL
    },
    {