Add `etcpak` library for faster ETC/ETC2/S3TC imports.

- `etc` module was renamed to `etcpak` and modified to use the new library.
- PKM importer is removed in the process, it's obsolete.
- Old library `etc2comp` is removed.
- S3TC compression no longer done via `squish` (but decompression still is).
- Slight modifications to etcpak sources for MinGW compatibility,
  to fix LLVM `-Wc++11-narrowing` errors, and to allow using vendored or
  system libpng.

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/thirdparty/etcpak/ColorSpace.hpp b/thirdparty/etcpak/ColorSpace.hpp
new file mode 100644
index 0000000000..c9d0a9cf3f
--- /dev/null
+++ b/thirdparty/etcpak/ColorSpace.hpp
@@ -0,0 +1,36 @@
+#ifndef __DARKRL__COLORSPACE_HPP__
+#define __DARKRL__COLORSPACE_HPP__
+
+#include "Vector.hpp"
+
+namespace Color
+{
+
+    class Lab;
+
+    class XYZ
+    {
+    public:
+        XYZ( float x, float y, float z );
+        XYZ( const v3b& rgb );
+        XYZ( const Lab& lab );
+
+        v3i RGB() const;
+
+        float x, y, z;
+    };
+
+    class Lab
+    {
+    public:
+        Lab();
+        Lab( float L, float a, float b );
+        Lab( const XYZ& xyz );
+        Lab( const v3b& rgb );
+
+        float L, a, b;
+    };
+
+}
+
+#endif