[babl] babl: add lut for some u8 conversions

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 0fa5f52be5671b31de521d221f2780fb13452794
Author: Øyvind Kolås <pippin gimp org>
Date:   Sun Jan 23 11:54:17 2022 +0100

    babl: add lut for some u8 conversions
    
    The fish path now marks created fishes that shall be monitored for
    usage and have full 24bit LUTs generated on demand when limits are
    exceeded. This 3-4x increases the throughput.

 babl/babl-fish-path.c | 43 +++++++++++++++++++++++++++++++++++++++++--
 babl/babl-fish.h      |  2 ++
 2 files changed, 43 insertions(+), 2 deletions(-)
---
diff --git a/babl/babl-fish-path.c b/babl/babl-fish-path.c
index f005a86..99b8380 100644
--- a/babl/babl-fish-path.c
+++ b/babl/babl-fish-path.c
@@ -552,6 +552,7 @@ babl_fish_path2 (const Babl *source,
     static const Babl *run_once[512]={NULL};
     int i;
     int done = 0;
+
     for (i = 0; run_once[i]; i++)
     {
       if (run_once[i] == source->format.space)
@@ -582,7 +583,6 @@ babl_fish_path2 (const Babl *source,
     {
       babl_conversion_class_for_each (show_item, (void*)source->format.space);
     }
-
   }
 
   babl = babl_calloc (1, sizeof (BablFishPath) +
@@ -601,6 +601,7 @@ babl_fish_path2 (const Babl *source,
   babl->fish_path.conversion_list = babl_list_init_with_size (BABL_HARD_MAX_PATH_LENGTH);
 
 
+
   {
     PathContext pc;
     int start_depth = max_path_length ();
@@ -652,6 +653,14 @@ babl_fish_path2 (const Babl *source,
     }
 
   _babl_fish_prepare_bpp (babl);
+  if (source->format.space != destination->format.space &&
+      babl->fish_path.source_bpp == babl->fish_path.dest_bpp &&
+      babl->fish_path.source_bpp == 4)
+  {
+     if ((source->format.model->flags & BABL_MODEL_FLAG_ASSOCIATED)==0)
+       babl->fish_path.is_u8_color_conv = 1;
+  }
+
   _babl_fish_rig_dispatch (babl);
   /* Since there is not an already registered instance by the required
    * name, inserting newly created class into database.
@@ -696,7 +705,6 @@ babl_fish_path (const Babl *source,
   return babl_fish_path2 (source, destination, 0.0);
 }
 
-
 static void
 babl_fish_path_process (const Babl *babl,
                         const char *source,
@@ -704,6 +712,37 @@ babl_fish_path_process (const Babl *babl,
                         long        n,
                         void       *data)
 {
+  if (babl->fish_path.is_u8_color_conv)
+  {
+     uint32_t *lut = (uint32_t*)babl->fish_path.u8_lut;
+     ((Babl*)babl)->fish.pixels += n;
+     if (!lut && babl->fish.pixels > 256 * 256)
+     {
+       ((Babl*)babl)->fish_path.u8_lut = malloc (256 * 256 * 256 * 4);
+       lut = (uint32_t*)babl->fish_path.u8_lut;
+       for (int o = 0; o < 256 * 256 * 256; o++)
+         lut[o] = o | 0xff000000;
+       process_conversion_path (babl->fish_path.conversion_list,
+                                lut,
+                                babl->fish_path.source_bpp,
+                                lut,
+                                babl->fish_path.dest_bpp,
+                                256*256*256);
+     }
+     if (lut)
+     {
+        uint32_t *src = (uint32_t*)source;
+        uint32_t *dst = (uint32_t*)destination;
+        lut = (uint32_t*)babl->fish_path.u8_lut;
+        while (n--)
+        {
+           uint32_t col = *src++;
+           uint32_t alpha = col & 0xff000000;
+           *dst++ = lut[col & 0xffffff] | alpha;
+        }
+        return;
+     }
+  }
   process_conversion_path (babl->fish_path.conversion_list,
                            source,
                            babl->fish_path.source_bpp,
diff --git a/babl/babl-fish.h b/babl/babl-fish.h
index 35382f0..966fa4e 100644
--- a/babl/babl-fish.h
+++ b/babl/babl-fish.h
@@ -69,6 +69,8 @@ typedef struct
   double     cost;   /* number of  ticks *10 + chain_length */
   int        source_bpp;
   int        dest_bpp;
+  unsigned int is_u8_color_conv:1; // keep track of count, and make 
+  uint8_t   *u8_lut;
   BablList  *conversion_list;
 } BablFishPath;