Uses MIPs for terrain textures previews following e4455a8e8f.

Comments By: Stan
Differential Revision: https://code.wildfiregames.com/D4447
This was SVN commit r26239.

source/lib/tex/tex.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2022 Wildfire Games.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -20,24 +20,19 @@
  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
-/*
- * support routines for 2d texture access/writing.
- */
-
 #include "precompiled.h"
+
 #include "tex.h"
 
-#include <math.h>
-#include <stdlib.h>
-#include <algorithm>
-
-#include "lib/timer.h"
-#include "lib/bits.h"
 #include "lib/allocators/shared_ptr.h"
+#include "lib/bits.h"
 #include "lib/sysdep/cpu.h"
+#include "lib/tex/tex_codec.h"
+#include "lib/timer.h"
 
-#include "tex_codec.h"
-
+#include <algorithm>
+#include <cmath>
+#include <cstdlib>
 
 static const StatusDefinition texStatusDefinitions[] = {
 	{ ERR::TEX_FMT_INVALID, L"Invalid/unsupported texture format" },
@@ -633,10 +628,35 @@ u8* Tex::get_data()
 
 	u8* p = m_Data.get();
 	if(!p)
-		return 0;
+		return nullptr;
 	return p + m_Ofs;
 }
 
+u8* Tex::GetMipLevelData(const u32 level)
+{
+	// (can't use normal CHECK_TEX due to u8* return value)
+	WARN_IF_ERR(validate());
+
+	u8* levelData = m_Data.get();
+	if (!levelData)
+		return nullptr;
+	levelData += m_Ofs;
+	const size_t dataPadding = (m_Flags & TEX_DXT) != 0 ? 4 : 1;
+	size_t levelWidth = m_Width, levelHeight = m_Height;
+	for (u32 currentLevel = 0; levelWidth > 1 || levelHeight > 1; ++currentLevel)
+	{
+		if (currentLevel == level)
+			return levelData;
+
+		const size_t levelDataSize = round_up(levelWidth, dataPadding) * round_up(levelHeight, dataPadding) * m_Bpp / 8;
+		levelData += levelDataSize;
+
+		levelWidth = std::max<u32>(levelWidth / 2, 1);
+		levelHeight = std::max<u32>(levelHeight / 2, 1);
+	}
+	return nullptr;
+}
+
 // returns color of 1x1 mipmap level
 u32 Tex::get_average_color() const
 {

source/lib/tex/tex.h

@@ -332,6 +332,14 @@ struct Tex
 	 **/
 	u8* get_data();
 
+	/**
+	 * return a pointer to the mip level image data (pixels).
+	 *
+	 * @param level which level's data should be returned.
+	 * @return pointer to the data.
+	 **/
+	u8* GetMipLevelData(const u32 level);
+
 	/**
 	 * return the ARGB value of the 1x1 mipmap level of the texture.
 	 *

source/tools/atlas/GameInterface/Handlers/TerrainHandlers.cpp

@@ -86,7 +86,7 @@ sTerrainTexturePreview GetPreview(CTerrainTextureEntry* tex, size_t width, size_
 		// Check that we can fit the texture into the preview size before any transform.
 		texture.m_Width >= width && texture.m_Height >= height &&
 		// Transform to a single format that we can process.
-		texture.transform_to((texture.m_Flags) & ~(TEX_DXT | TEX_MIPMAPS | TEX_GREY | TEX_BGR)) == INFO::OK &&
+		texture.transform_to((texture.m_Flags | TEX_MIPMAPS) & ~(TEX_DXT | TEX_GREY | TEX_BGR)) == INFO::OK &&
 		(texture.m_Bpp == 24 || texture.m_Bpp == 32);
 	if (canUsePreview)
 	{
@@ -95,14 +95,17 @@ sTerrainTexturePreview GetPreview(CTerrainTextureEntry* tex, size_t width, size_
 			++level;
 		// Extract the middle section (as a representative preview),
 		// and copy into buffer.
-		u8* data = texture.get_data();
-		const size_t dataShiftX = ((texture.m_Width - width) / 2) >> level;
-		const size_t dataShiftY = ((texture.m_Height - height) / 2) >> level;
+		u8* data = texture.GetMipLevelData(level);
+		ENSURE(data);
+		const size_t levelWidth = texture.m_Width >> level;
+		const size_t levelHeight = texture.m_Height >> level;
+		const size_t dataShiftX = (levelWidth - width) / 2;
+		const size_t dataShiftY = (levelHeight - height) / 2;
 		for (size_t y = 0; y < height; ++y)
 			for (size_t x = 0; x < width; ++x)
 			{
 				const size_t bufferOffset = (y * width + x) * previewBPP;
-				const size_t dataOffset = (((y << level) + dataShiftY) * texture.m_Width + (x << level) + dataShiftX) * texture.m_Bpp / 8;
+				const size_t dataOffset = ((y + dataShiftY) * levelWidth + x + dataShiftX) * texture.m_Bpp / 8;
 				buffer[bufferOffset + 0] = data[dataOffset + 0];
 				buffer[bufferOffset + 1] = data[dataOffset + 1];
 				buffer[bufferOffset + 2] = data[dataOffset + 2];