Reland: Add ETC1 powered SSE encoder for tile texture compression

cc/resources/texture_compressor_etc1.cc

Index: cc/resources/texture_compressor_etc1.cc
diff --git a/cc/resources/texture_compressor_etc1.cc b/cc/resources/texture_compressor_etc1.cc
index 61c4438c21862342f8cf0ca10b19a375364a581c..03055437be666d533f9ae99c651d2568fd8baab1 100644
--- a/cc/resources/texture_compressor_etc1.cc
+++ b/cc/resources/texture_compressor_etc1.cc
@@ -20,194 +20,21 @@
 
 namespace {
 
-template <typename T>
-inline T clamp(T val, T min, T max) {
-  return val < min ? min : (val > max ? max : val);
-}
-
-inline uint8_t round_to_5_bits(float val) {
-  return clamp<uint8_t>(val * 31.0f / 255.0f + 0.5f, 0, 31);
-}
-
-inline uint8_t round_to_4_bits(float val) {
-  return clamp<uint8_t>(val * 15.0f / 255.0f + 0.5f, 0, 15);
-}
-
-union Color {
-  struct BgraColorType {
-    uint8_t b;
-    uint8_t g;
-    uint8_t r;
-    uint8_t a;
-  } channels;
-  uint8_t components[4];
-  uint32_t bits;
-};
-
-/*
- * Codeword tables.
- * See: Table 3.17.2
- */
-static const int16_t g_codeword_tables[8][4] = {{-8, -2, 2, 8},
-                                                {-17, -5, 5, 17},
-                                                {-29, -9, 9, 29},
-                                                {-42, -13, 13, 42},
-                                                {-60, -18, 18, 60},
-                                                {-80, -24, 24, 80},
-                                                {-106, -33, 33, 106},
-                                                {-183, -47, 47, 183}};
-
-/*
- * Maps modifier indices to pixel index values.
- * See: Table 3.17.3
- */
-static const uint8_t g_mod_to_pix[4] = {3, 2, 0, 1};
-
-/*
- * The ETC1 specification index texels as follows:
- *
- * [a][e][i][m]     [ 0][ 4][ 8][12]
- * [b][f][j][n] <-> [ 1][ 5][ 9][13]
- * [c][g][k][o]     [ 2][ 6][10][14]
- * [d][h][l][p]     [ 3][ 7][11][15]
- *
- * However, when extracting sub blocks from BGRA data the natural array
- * indexing order ends up different:
- *
- * vertical0: [a][e][b][f]  horizontal0: [a][e][i][m]
- *            [c][g][d][h]               [b][f][j][n]
- * vertical1: [i][m][j][n]  horizontal1: [c][g][k][o]
- *            [k][o][l][p]               [d][h][l][p]
- *
- * In order to translate from the natural array indices in a sub block to the
- * indices (number) used by specification and hardware we use this table.
- */
-static const uint8_t g_idx_to_num[4][8] = {
-    {0, 4, 1, 5, 2, 6, 3, 7},        // Vertical block 0.
-    {8, 12, 9, 13, 10, 14, 11, 15},  // Vertical block 1.
-    {0, 4, 8, 12, 1, 5, 9, 13},      // Horizontal block 0.
-    {2, 6, 10, 14, 3, 7, 11, 15}     // Horizontal block 1.
-};
-
-inline void WriteColors444(uint8_t* block,
-                           const Color& color0,
-                           const Color& color1) {
-  block[0] = (color0.channels.r & 0xf0) | (color1.channels.r >> 4);
-  block[1] = (color0.channels.g & 0xf0) | (color1.channels.g >> 4);
-  block[2] = (color0.channels.b & 0xf0) | (color1.channels.b >> 4);
-}
-
-inline void WriteColors555(uint8_t* block,
-                           const Color& color0,
-                           const Color& color1) {
-  // Table for conversion to 3-bit two complement format.
-  static const uint8_t two_compl_trans_table[8] = {
-      4,  // -4 (100b)
-      5,  // -3 (101b)
-      6,  // -2 (110b)
-      7,  // -1 (111b)
-      0,  //  0 (000b)
-      1,  //  1 (001b)
-      2,  //  2 (010b)
-      3,  //  3 (011b)
-  };
-
-  int16_t delta_r =
-      static_cast<int16_t>(color1.channels.r >> 3) - (color0.channels.r >> 3);
-  int16_t delta_g =
-      static_cast<int16_t>(color1.channels.g >> 3) - (color0.channels.g >> 3);
-  int16_t delta_b =
-      static_cast<int16_t>(color1.channels.b >> 3) - (color0.channels.b >> 3);
-  DCHECK(delta_r >= -4 && delta_r <= 3);
-  DCHECK(delta_g >= -4 && delta_g <= 3);
-  DCHECK(delta_b >= -4 && delta_b <= 3);
-
-  block[0] = (color0.channels.r & 0xf8) | two_compl_trans_table[delta_r + 4];
-  block[1] = (color0.channels.g & 0xf8) | two_compl_trans_table[delta_g + 4];
-  block[2] = (color0.channels.b & 0xf8) | two_compl_trans_table[delta_b + 4];
-}
-
-inline void WriteCodewordTable(uint8_t* block,
-                               uint8_t sub_block_id,
-                               uint8_t table) {
-  DCHECK_LT(sub_block_id, 2);
-  DCHECK_LT(table, 8);
-
-  uint8_t shift = (2 + (3 - sub_block_id * 3));
-  block[3] &= ~(0x07 << shift);
-  block[3] |= table << shift;
-}
-
-inline void WritePixelData(uint8_t* block, uint32_t pixel_data) {
-  block[4] |= pixel_data >> 24;
-  block[5] |= (pixel_data >> 16) & 0xff;
-  block[6] |= (pixel_data >> 8) & 0xff;
-  block[7] |= pixel_data & 0xff;
-}
-
-inline void WriteFlip(uint8_t* block, bool flip) {
-  block[3] &= ~0x01;
-  block[3] |= static_cast<uint8_t>(flip);
-}
-
-inline void WriteDiff(uint8_t* block, bool diff) {
-  block[3] &= ~0x02;
-  block[3] |= static_cast<uint8_t>(diff) << 1;
-}
-
-/**
- * Compress and rounds BGR888 into BGR444. The resulting BGR444 color is
- * expanded to BGR888 as it would be in hardware after decompression. The
- * actual 444-bit data is available in the four most significant bits of each
- * channel.
- */
-inline Color MakeColor444(const float* bgr) {
-  uint8_t b4 = round_to_4_bits(bgr[0]);
-  uint8_t g4 = round_to_4_bits(bgr[1]);
-  uint8_t r4 = round_to_4_bits(bgr[2]);
-  Color bgr444;
-  bgr444.channels.b = (b4 << 4) | b4;
-  bgr444.channels.g = (g4 << 4) | g4;
-  bgr444.channels.r = (r4 << 4) | r4;
-  return bgr444;
-}
-
-/**
- * Compress and rounds BGR888 into BGR555. The resulting BGR555 color is
- * expanded to BGR888 as it would be in hardware after decompression. The
- * actual 555-bit data is available in the five most significant bits of each
- * channel.
- */
-inline Color MakeColor555(const float* bgr) {
-  uint8_t b5 = round_to_5_bits(bgr[0]);
-  uint8_t g5 = round_to_5_bits(bgr[1]);
-  uint8_t r5 = round_to_5_bits(bgr[2]);
-  Color bgr555;
-  bgr555.channels.b = (b5 << 3) | (b5 >> 2);
-  bgr555.channels.g = (g5 << 3) | (g5 >> 2);
-  bgr555.channels.r = (r5 << 3) | (r5 >> 2);
-  return bgr555;
-}
-
-/**
- * Constructs a color from a given base color and luminance value.
- */
-inline Color MakeColor(const Color& base, int16_t lum) {
+// Constructs a color from a given base color and luminance value.
+inline cc::Color MakeColor(const cc::Color& base, int16_t lum) {
   int b = static_cast<int>(base.channels.b) + lum;
   int g = static_cast<int>(base.channels.g) + lum;
   int r = static_cast<int>(base.channels.r) + lum;
-  Color color;
-  color.channels.b = static_cast<uint8_t>(clamp(b, 0, 255));
-  color.channels.g = static_cast<uint8_t>(clamp(g, 0, 255));
-  color.channels.r = static_cast<uint8_t>(clamp(r, 0, 255));
+  cc::Color color;
+  color.channels.b = static_cast<uint8_t>(cc::clamp(b, 0, 255));
+  color.channels.g = static_cast<uint8_t>(cc::clamp(g, 0, 255));
+  color.channels.r = static_cast<uint8_t>(cc::clamp(r, 0, 255));
   return color;
 }
 
-/**
- * Calculates the error metric for two colors. A small error signals that the
- * colors are similar to each other, a large error the signals the opposite.
- */
-inline uint32_t GetColorError(const Color& u, const Color& v) {
+// Calculates the error metric for two colors. A small error signals that the
+// colors are similar to each other, a large error the signals the opposite.
+inline uint32_t GetColorError(const cc::Color& u, const cc::Color& v) {
 #ifdef USE_PERCEIVED_ERROR_METRIC
   float delta_b = static_cast<float>(u.channels.b) - v.channels.b;
   float delta_g = static_cast<float>(u.channels.g) - v.channels.g;
@@ -223,7 +50,7 @@ inline uint32_t GetColorError(const Color& u, const Color& v) {
 #endif
 }
 
-void GetAverageColor(const Color* src, float* avg_color) {
+void GetAverageColor(const cc::Color* src, float* avg_color) {
   uint32_t sum_b = 0, sum_g = 0, sum_r = 0;
 
   for (unsigned int i = 0; i < 8; ++i) {
@@ -239,8 +66,8 @@ void GetAverageColor(const Color* src, float* avg_color) {
 }
 
 void ComputeLuminance(uint8_t* block,
-                      const Color* src,
-                      const Color& base,
+                      const cc::Color* src,
+                      const cc::Color& base,
                       int sub_block_id,
                       const uint8_t* idx_to_num_tab) {
   uint32_t best_tbl_err = std::numeric_limits<uint32_t>::max();
@@ -252,9 +79,9 @@ void ComputeLuminance(uint8_t* block,
   for (unsigned int tbl_idx = 0; tbl_idx < 8; ++tbl_idx) {
     // Pre-compute all the candidate colors; combinations of the base color and
     // all available luminance values.
-    Color candidate_color[4];  // [modifier]
+    cc::Color candidate_color[4];  // [modifier]
     for (unsigned int mod_idx = 0; mod_idx < 4; ++mod_idx) {
-      int16_t lum = g_codeword_tables[tbl_idx][mod_idx];
+      int16_t lum = cc::g_codeword_tables[tbl_idx][mod_idx];
       candidate_color[mod_idx] = MakeColor(base, lum);
     }
 
@@ -265,7 +92,7 @@ void ComputeLuminance(uint8_t* block,
       // smallest error.
       uint32_t best_mod_err = std::numeric_limits<uint32_t>::max();
       for (unsigned int mod_idx = 0; mod_idx < 4; ++mod_idx) {
-        const Color& color = candidate_color[mod_idx];
+        const cc::Color& color = candidate_color[mod_idx];
 
         uint32_t mod_err = GetColorError(src[i], color);
         if (mod_err < best_mod_err) {
@@ -291,13 +118,13 @@ void ComputeLuminance(uint8_t* block,
     }
   }
 
-  WriteCodewordTable(block, sub_block_id, best_tbl_idx);
+  cc::WriteCodewordTable(block, sub_block_id, best_tbl_idx);
 
   uint32_t pix_data = 0;
 
   for (unsigned int i = 0; i < 8; ++i) {
     uint8_t mod_idx = best_mod_idx[best_tbl_idx][i];
-    uint8_t pix_idx = g_mod_to_pix[mod_idx];
+    uint8_t pix_idx = cc::g_mod_to_pix[mod_idx];
 
     uint32_t lsb = pix_idx & 0x1;
     uint32_t msb = pix_idx >> 1;
@@ -308,7 +135,7 @@ void ComputeLuminance(uint8_t* block,
     pix_data |= lsb << (texel_num);
   }
 
-  WritePixelData(block, pix_data);
+  cc::WritePixelData(block, pix_data);
 }
 
 /**
@@ -316,7 +143,7 @@ void ComputeLuminance(uint8_t* block,
  * block. If it's not the function will bail out without writing anything to
  * the destination buffer.
  */
-bool TryCompressSolidBlock(uint8_t* dst, const Color* src) {
+bool TryCompressSolidBlock(uint8_t* dst, const cc::Color* src) {
   for (unsigned int i = 1; i < 16; ++i) {
     if (src[i].bits != src[0].bits)
       return false;
@@ -328,11 +155,11 @@ bool TryCompressSolidBlock(uint8_t* dst, const Color* src) {
   float src_color_float[3] = {static_cast<float>(src->channels.b),
                               static_cast<float>(src->channels.g),
                               static_cast<float>(src->channels.r)};
-  Color base = MakeColor555(src_color_float);
+  cc::Color base = cc::MakeColor555(src_color_float);
 
-  WriteDiff(dst, true);
-  WriteFlip(dst, false);
-  WriteColors555(dst, base, base);
+  cc::WriteDiff(dst, true);
+  cc::WriteFlip(dst, false);
+  cc::WriteColors555(dst, base, base);
 
   uint8_t best_tbl_idx = 0;
   uint8_t best_mod_idx = 0;
@@ -344,8 +171,8 @@ bool TryCompressSolidBlock(uint8_t* dst, const Color* src) {
     // Try all modifiers in the current table to find which one gives the
     // smallest error.
     for (unsigned int mod_idx = 0; mod_idx < 4; ++mod_idx) {
-      int16_t lum = g_codeword_tables[tbl_idx][mod_idx];
-      const Color& color = MakeColor(base, lum);
+      int16_t lum = cc::g_codeword_tables[tbl_idx][mod_idx];
+      const cc::Color& color = MakeColor(base, lum);
 
       uint32_t mod_err = GetColorError(*src, color);
       if (mod_err < best_mod_err) {
@@ -362,10 +189,10 @@ bool TryCompressSolidBlock(uint8_t* dst, const Color* src) {
       break;
   }
 
-  WriteCodewordTable(dst, 0, best_tbl_idx);
-  WriteCodewordTable(dst, 1, best_tbl_idx);
+  cc::WriteCodewordTable(dst, 0, best_tbl_idx);
+  cc::WriteCodewordTable(dst, 1, best_tbl_idx);
 
-  uint8_t pix_idx = g_mod_to_pix[best_mod_idx];
+  uint8_t pix_idx = cc::g_mod_to_pix[best_mod_idx];
   uint32_t lsb = pix_idx & 0x1;
   uint32_t msb = pix_idx >> 1;
 
@@ -373,23 +200,26 @@ bool TryCompressSolidBlock(uint8_t* dst, const Color* src) {
   for (unsigned int i = 0; i < 2; ++i) {
     for (unsigned int j = 0; j < 8; ++j) {
       // Obtain the texel number as specified in the standard.
-      int texel_num = g_idx_to_num[i][j];
+      int texel_num = cc::g_idx_to_num[i][j];
       pix_data |= msb << (texel_num + 16);
       pix_data |= lsb << (texel_num);
     }
   }
 
-  WritePixelData(dst, pix_data);
+  cc::WritePixelData(dst, pix_data);
   return true;
 }
 
-void CompressBlock(uint8_t* dst, const Color* ver_src, const Color* hor_src) {
+void CompressBlock(uint8_t* dst,
+                   const cc::Color* ver_src,
+                   const cc::Color* hor_src) {
   if (TryCompressSolidBlock(dst, ver_src))
     return;
 
-  const Color* sub_block_src[4] = {ver_src, ver_src + 8, hor_src, hor_src + 8};
+  const cc::Color* sub_block_src[4] = {
+      ver_src, ver_src + 8, hor_src, hor_src + 8};
 
-  Color sub_block_avg[4];
+  cc::Color sub_block_avg[4];
   bool use_differential[2] = {true, true};
 
   // Compute the average color for each sub block and determine if differential
@@ -397,11 +227,11 @@ void CompressBlock(uint8_t* dst, const Color* ver_src, const Color* hor_src) {
   for (unsigned int i = 0, j = 1; i < 4; i += 2, j += 2) {
     float avg_color_0[3];
     GetAverageColor(sub_block_src[i], avg_color_0);
-    Color avg_color_555_0 = MakeColor555(avg_color_0);
+    cc::Color avg_color_555_0 = cc::MakeColor555(avg_color_0);
 
     float avg_color_1[3];
     GetAverageColor(sub_block_src[j], avg_color_1);
-    Color avg_color_555_1 = MakeColor555(avg_color_1);
+    cc::Color avg_color_555_1 = cc::MakeColor555(avg_color_1);
 
     for (unsigned int light_idx = 0; light_idx < 3; ++light_idx) {
       int u = avg_color_555_0.components[light_idx] >> 3;
@@ -410,8 +240,8 @@ void CompressBlock(uint8_t* dst, const Color* ver_src, const Color* hor_src) {
       int component_diff = v - u;
       if (component_diff < -4 || component_diff > 3) {
         use_differential[i / 2] = false;
-        sub_block_avg[i] = MakeColor444(avg_color_0);
-        sub_block_avg[j] = MakeColor444(avg_color_1);
+        sub_block_avg[i] = cc::MakeColor444(avg_color_0);
+        sub_block_avg[j] = cc::MakeColor444(avg_color_1);
       } else {
         sub_block_avg[i] = avg_color_555_0;
         sub_block_avg[j] = avg_color_555_1;
@@ -435,28 +265,28 @@ void CompressBlock(uint8_t* dst, const Color* ver_src, const Color* hor_src) {
   // Clear destination buffer so that we can "or" in the results.
   memset(dst, 0, 8);
 
-  WriteDiff(dst, use_differential[!!flip]);
-  WriteFlip(dst, flip);
+  cc::WriteDiff(dst, use_differential[!!flip]);
+  cc::WriteFlip(dst, flip);
 
   uint8_t sub_block_off_0 = flip ? 2 : 0;
   uint8_t sub_block_off_1 = sub_block_off_0 + 1;
 
   if (use_differential[!!flip]) {
-    WriteColors555(dst, sub_block_avg[sub_block_off_0],
-                   sub_block_avg[sub_block_off_1]);
+    cc::WriteColors555(dst, sub_block_avg[sub_block_off_0],
+                       sub_block_avg[sub_block_off_1]);
   } else {
-    WriteColors444(dst, sub_block_avg[sub_block_off_0],
-                   sub_block_avg[sub_block_off_1]);
+    cc::WriteColors444(dst, sub_block_avg[sub_block_off_0],
+                       sub_block_avg[sub_block_off_1]);
   }
 
   // Compute luminance for the first sub block.
   ComputeLuminance(dst, sub_block_src[sub_block_off_0],
                    sub_block_avg[sub_block_off_0], 0,
-                   g_idx_to_num[sub_block_off_0]);
+                   cc::g_idx_to_num[sub_block_off_0]);
   // Compute luminance for the second sub block.
   ComputeLuminance(dst, sub_block_src[sub_block_off_1],
                    sub_block_avg[sub_block_off_1], 1,
-                   g_idx_to_num[sub_block_off_1]);
+                   cc::g_idx_to_num[sub_block_off_1]);
 }
 
 }  // namespace
@@ -468,8 +298,10 @@ void TextureCompressorETC1::Compress(const uint8_t* src,
                                      int width,
                                      int height,
                                      Quality quality) {
-  DCHECK(width >= 4 && (width & 3) == 0);
-  DCHECK(height >= 4 && (height & 3) == 0);
+  DCHECK_GE(width, 4);
+  DCHECK_EQ((width & 3), 0);
+  DCHECK_GE(height, 4);
+  DCHECK_EQ((height & 3), 0);
 
   Color ver_blocks[16];
   Color hor_blocks[16];