egg: Add (discouraged) way to specify sRGB texture format (#924)

This should NOT be used by exporters, but is provided only for the sake of round-trippability of .bam files.

panda/src/egg/eggTexture.cxx

@@ -509,6 +509,7 @@ has_alpha_channel(int num_components) const {
   case F_rgb8:
   case F_rgb5:
   case F_rgb332:
+  case F_srgb:
     // These formats never use alpha, regardless of the number of components
     // we have.
     return false;
@@ -525,6 +526,7 @@ has_alpha_channel(int num_components) const {
   case F_rgba8:
   case F_rgba4:
   case F_rgba5:
+  case F_srgb_alpha:
   case F_unspecified:
     // These formats use alpha if the image had alpha.
     return (num_components == 2 || num_components == 4);
@@ -690,6 +692,8 @@ EggTexture::Format EggTexture::
 string_format(const string &string) {
   if (cmp_nocase_uh(string, "rgba") == 0) {
     return F_rgba;
+  } else if (cmp_nocase_uh(string, "srgb_alpha") == 0) {
+    return F_srgb_alpha;
   } else if (cmp_nocase_uh(string, "rgbm") == 0) {
     return F_rgbm;
   } else if (cmp_nocase_uh(string, "rgba12") == 0) {
@@ -701,6 +705,8 @@ string_format(const string &string) {
 
   } else if (cmp_nocase_uh(string, "rgb") == 0) {
     return F_rgb;
+  } else if (cmp_nocase_uh(string, "srgb") == 0) {
+    return F_srgb;
   } else if (cmp_nocase_uh(string, "rgb12") == 0) {
     return F_rgb12;
   } else if (cmp_nocase_uh(string, "rgb8") == 0) {
@@ -1137,6 +1143,8 @@ ostream &operator << (ostream &out, EggTexture::Format format) {
     return out << "rgba8";
   case EggTexture::F_rgba4:
     return out << "rgba4";
+  case EggTexture::F_srgb_alpha:
+    return out << "srgb_alpha";
 
   case EggTexture::F_rgb:
     return out << "rgb";
@@ -1150,6 +1158,8 @@ ostream &operator << (ostream &out, EggTexture::Format format) {
     return out << "rgba5";
   case EggTexture::F_rgb332:
     return out << "rgb332";
+  case EggTexture::F_srgb:
+    return out << "srgb";
 
   case EggTexture::F_red:
     return out << "red";

panda/src/egg/eggTexture.h

@@ -60,7 +60,10 @@ PUBLISHED:
     F_rgba, F_rgbm, F_rgba12, F_rgba8, F_rgba4, F_rgba5,
     F_rgb, F_rgb12, F_rgb8, F_rgb5, F_rgb332,
     F_red, F_green, F_blue, F_alpha, F_luminance,
-    F_luminance_alpha, F_luminance_alphamask
+    F_luminance_alpha, F_luminance_alphamask,
+
+    // Only for compatibility with .bam, use is discouraged!
+    F_srgb, F_srgb_alpha
   };
   enum CompressionMode {
     CM_default, CM_off, CM_on,

panda/src/egg2pg/eggLoader.cxx

@@ -900,6 +900,7 @@ load_texture(TextureDef &def, EggTexture *egg_tex) {
   case EggTexture::F_rgb8:
   case EggTexture::F_rgb5:
   case EggTexture::F_rgb332:
+  case EggTexture::F_srgb:
     wanted_channels = 3;
     wanted_alpha = false;
     break;
@@ -910,6 +911,7 @@ load_texture(TextureDef &def, EggTexture *egg_tex) {
   case EggTexture::F_rgba8:
   case EggTexture::F_rgba4:
   case EggTexture::F_rgba5:
+  case EggTexture::F_srgb_alpha:
     wanted_channels = 4;
     wanted_alpha = true;
     break;
@@ -1259,6 +1261,10 @@ apply_texture_attributes(Texture *tex, const EggTexture *egg_tex) {
     case EggTexture::F_rgb332:
       tex->set_format(Texture::F_rgb332);
       break;
+    case EggTexture::F_srgb:
+    case EggTexture::F_srgb_alpha:
+      tex->set_format(Texture::F_srgb);
+      break;
 
     case EggTexture::F_unspecified:
       break;
@@ -1296,6 +1302,9 @@ apply_texture_attributes(Texture *tex, const EggTexture *egg_tex) {
     case EggTexture::F_rgba5:
       tex->set_format(Texture::F_rgba5);
       break;
+    case EggTexture::F_srgb_alpha:
+      tex->set_format(Texture::F_srgb_alpha);
+      break;
 
     case EggTexture::F_unspecified:
       break;

panda/src/egg2pg/eggSaver.cxx

@@ -1420,6 +1420,12 @@ get_egg_texture(Texture *tex) {
       case Texture::F_luminance_alphamask:
         temp.set_format(EggTexture::F_luminance_alphamask);
         break;
+      case Texture::F_srgb:
+        temp.set_format(EggTexture::F_srgb);
+        break;
+      case Texture::F_srgb_alpha:
+        temp.set_format(EggTexture::F_srgb_alpha);
+        break;
       default:
         break;
       }