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, 77 insertions, 0 deletions

diff --git a/thirdparty/etcpak/DataProvider.cpp b/thirdparty/etcpak/DataProvider.cpp
new file mode 100644
index 0000000000..6bd4b105ed
--- /dev/null
+++ b/thirdparty/etcpak/DataProvider.cpp
@@ -0,0 +1,77 @@
+#include <assert.h>
+#include <utility>
+
+#include "BitmapDownsampled.hpp"
+#include "DataProvider.hpp"
+#include "MipMap.hpp"
+
+DataProvider::DataProvider( const char* fn, bool mipmap, bool bgr )
+    : m_offset( 0 )
+    , m_mipmap( mipmap )
+    , m_done( false )
+    , m_lines( 32 )
+{
+    m_bmp.emplace_back( new Bitmap( fn, m_lines, bgr ) );
+    m_current = m_bmp[0].get();
+}
+
+DataProvider::~DataProvider()
+{
+}
+
+unsigned int DataProvider::NumberOfParts() const
+{
+    unsigned int parts = ( ( m_bmp[0]->Size().y / 4 ) + m_lines - 1 ) / m_lines;
+
+    if( m_mipmap )
+    {
+        v2i current = m_bmp[0]->Size();
+        int levels = NumberOfMipLevels( current );
+        unsigned int lines = m_lines;
+        for( int i=1; i<levels; i++ )
+        {
+            assert( current.x != 1 || current.y != 1 );
+            current.x = std::max( 1, current.x / 2 );
+            current.y = std::max( 1, current.y / 2 );
+            lines *= 2;
+            parts += ( ( std::max( 4, current.y ) / 4 ) + lines - 1 ) / lines;
+        }
+        assert( current.x == 1 && current.y == 1 );
+    }
+
+    return parts;
+}
+
+DataPart DataProvider::NextPart()
+{
+    assert( !m_done );
+
+    unsigned int lines = m_lines;
+    bool done;
+
+    const auto ptr = m_current->NextBlock( lines, done );
+    DataPart ret = {
+        ptr,
+        std::max<unsigned int>( 4, m_current->Size().x ),
+        lines,
+        m_offset
+    };
+
+    m_offset += m_current->Size().x / 4 * lines;
+
+    if( done )
+    {
+        if( m_mipmap && ( m_current->Size().x != 1 || m_current->Size().y != 1 ) )
+        {
+            m_lines *= 2;
+            m_bmp.emplace_back( new BitmapDownsampled( *m_current, m_lines ) );
+            m_current = m_bmp[m_bmp.size()-1].get();
+        }
+        else
+        {
+            m_done = true;
+        }
+    }
+
+    return ret;
+}