[AI] Add tensor:scale_add_planes to Lua API for raw-denoise color fix

src/lua/ai.c

@@ -414,6 +414,64 @@ static int _tensor_scale_add(lua_State *L)
   return 1;
 }
 
+// tensor:scale_add_planes({scales} [, {offsets}]) → self
+// in-place per-plane: t[k,...] = t[k,...] * scales[k+1] + offsets[k+1].
+// 1-indexed tables, one entry per channel plane (dim 1). offsets
+// defaults to 0. Requires ndim >= 2 and shape[0] == 1.
+static int _tensor_scale_add_planes(lua_State *L)
+{
+  dt_lua_ai_tensor_t *t
+    = luaL_checkudata(L, 1, "dt_lua_ai_tensor_t");
+  if(!t->data) return luaL_error(L, "tensor has been freed");
+  luaL_checktype(L, 2, LUA_TTABLE);
+  const gboolean has_offsets = !lua_isnoneornil(L, 3);
+  if(has_offsets) luaL_checktype(L, 3, LUA_TTABLE);
+  if(t->ndim < 2 || t->shape[0] != 1)
+    return luaL_error(L, "scale_add_planes requires [1,C,...] tensor");
+  const size_t C = (size_t)t->shape[1];
+
+  float *scales = g_new0(float, C);
+  float *offsets = g_new0(float, C);
+  for(size_t k = 0; k < C; k++)
+  {
+    lua_rawgeti(L, 2, (int)(k + 1));
+    if(!lua_isnumber(L, -1))
+    {
+      g_free(scales); g_free(offsets);
+      return luaL_error(L, "scales[%d] is not a number", (int)(k + 1));
+    }
+    scales[k] = (float)lua_tonumber(L, -1);
+    lua_pop(L, 1);
+    if(has_offsets)
+    {
+      lua_rawgeti(L, 3, (int)(k + 1));
+      if(!lua_isnumber(L, -1))
+      {
+        g_free(scales); g_free(offsets);
+        return luaL_error(L, "offsets[%d] is not a number", (int)(k + 1));
+      }
+      offsets[k] = (float)lua_tonumber(L, -1);
+      lua_pop(L, 1);
+    }
+  }
+
+  size_t plane = 1;
+  for(int d = 2; d < t->ndim; d++) plane *= (size_t)t->shape[d];
+
+  for(size_t k = 0; k < C; k++)
+  {
+    float *p = t->data + k * plane;
+    const float s = scales[k];
+    const float o = offsets[k];
+    for(size_t i = 0; i < plane; i++) p[i] = p[i] * s + o;
+  }
+
+  g_free(scales);
+  g_free(offsets);
+  lua_settop(L, 1);
+  return 1;
+}
+
 // tensor:sum() → float
 // sum of all elements (double accumulation, returned as Lua number)
 static int _tensor_sum(lua_State *L)
@@ -1672,6 +1730,8 @@ int dt_lua_init_ai(lua_State *L)
   lua_setfield(L, -2, "fill");
   lua_pushcfunction(L, _tensor_scale_add);
   lua_setfield(L, -2, "scale_add");
+  lua_pushcfunction(L, _tensor_scale_add_planes);
+  lua_setfield(L, -2, "scale_add_planes");
   lua_pushcfunction(L, _tensor_sum);
   lua_setfield(L, -2, "sum");
   lua_pushcfunction(L, _tensor_mean);