1 files changed, 106 insertions, 0 deletions
diff --git a/thirdparty/etcpak/ProcessRgtc.cpp b/thirdparty/etcpak/ProcessRgtc.cpp
new file mode 100644
index 0000000000..3a283b743b
--- /dev/null
+++ b/thirdparty/etcpak/ProcessRgtc.cpp
@@ -0,0 +1,106 @@
+// -- GODOT start --
+
+#include "ForceInline.hpp"
+#include "ProcessRgtc.hpp"
+
+#include <assert.h>
+#include <string.h>
+
+static const uint8_t AlphaIndexTable[8] = { 1, 7, 6, 5, 4, 3, 2, 0 };
+
+static etcpak_force_inline uint64_t ProcessAlpha( const uint8_t* src )
+{
+    uint8_t solid8 = *src;
+    uint16_t solid16 = uint16_t( solid8 ) | ( uint16_t( solid8 ) << 8 );
+    uint32_t solid32 = uint32_t( solid16 ) | ( uint32_t( solid16 ) << 16 );
+    uint64_t solid64 = uint64_t( solid32 ) | ( uint64_t( solid32 ) << 32 );
+    if( memcmp( src, &solid64, 8 ) == 0 && memcmp( src+8, &solid64, 8 ) == 0 )
+    {
+        return solid8;
+    }
+
+    uint8_t min = src[0];
+    uint8_t max = min;
+    for( int i=1; i<16; i++ )
+    {
+        const auto v = src[i];
+        if( v > max ) max = v;
+        else if( v < min ) min = v;
+    }
+
+    uint32_t range = ( 8 << 13 ) / ( 1 + max - min );
+    uint64_t data = 0;
+    for( int i=0; i<16; i++ )
+    {
+        uint8_t a = src[i] - min;
+        uint64_t idx = AlphaIndexTable[( a * range ) >> 13];
+        data |= idx << (i*3);
+    }
+
+    return max | ( min << 8 ) | ( data << 16 );
+}
+
+void CompressRgtcR(const uint32_t *src, uint64_t *dst, uint32_t blocks, size_t width) 
+{
+	int i = 0;
+	auto ptr = dst;
+	do 
+	{
+		uint32_t rgba[4 * 4];
+		uint8_t r[4 * 4];
+
+		auto tmp = (char *)rgba;
+		memcpy(tmp, src + width * 0, 4 * 4);
+		memcpy(tmp + 4 * 4, src + width * 1, 4 * 4);
+		memcpy(tmp + 8 * 4, src + width * 2, 4 * 4);
+		memcpy(tmp + 12 * 4, src + width * 3, 4 * 4);
+		src += 4;
+		if (++i == width / 4) 
+		{
+			src += width * 3;
+			i = 0;
+		}
+
+		for (int i = 0; i < 16; i++) 
+		{
+			r[i] = rgba[i] & 0x000000FF;
+		}
+		*ptr++ = ProcessAlpha(r);
+	} 
+	while (--blocks);
+}
+
+void CompressRgtcRG(const uint32_t *src, uint64_t *dst, uint32_t blocks, size_t width) 
+{
+	int i = 0;
+	auto ptr = dst;
+	do 
+	{
+		uint32_t rgba[4 * 4];
+		uint8_t r[4 * 4];
+		uint8_t g[4 * 4];
+
+		auto tmp = (char *)rgba;
+		memcpy(tmp, src + width * 0, 4 * 4);
+		memcpy(tmp + 4 * 4, src + width * 1, 4 * 4);
+		memcpy(tmp + 8 * 4, src + width * 2, 4 * 4);
+		memcpy(tmp + 12 * 4, src + width * 3, 4 * 4);
+		src += 4;
+		if (++i == width / 4) 
+		{
+			src += width * 3;
+			i = 0;
+		}
+
+		for (int i = 0; i < 16; i++) 
+		{
+			r[i] = rgba[i] & 0x000000FF;
+			g[i] = (rgba[i] & 0x0000FF00) >> 8;
+		}
+		*ptr++ = ProcessAlpha(r);
+		*ptr++ = ProcessAlpha(g);
+	} 
+	while (--blocks);
+}
+
+// -- GODOT end --