From fa8250ba1215577ffb24aafbee6e18dbfb81f769 Mon Sep 17 00:00:00 2001
From: Peter Thoman <peter@metaclassofnil.com>
Date: Fri, 3 May 2013 13:35:24 +0200
Subject: [PATCH] Avoid scaling empty and flat textures

---
 GPU/GLES/TextureScaler.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/GPU/GLES/TextureScaler.cpp b/GPU/GLES/TextureScaler.cpp
index 036dea50a3..f810f55b3a 100644
--- a/GPU/GLES/TextureScaler.cpp
+++ b/GPU/GLES/TextureScaler.cpp
@@ -40,6 +40,8 @@ namespace p = std::placeholders;
 #include "native/base/timeutil.h"
 #endif
 
+/////////////////////////////////////// Helper Functions (mostly math for parallelization)
+
 namespace {
 	// convert 4444 image to 8888, parallelizable
 	void convert4444(u16* data, u32* out, int width, int l, int u) {
@@ -261,11 +263,28 @@ namespace {
 	}
 }
 
+/////////////////////////////////////// Texture Scaler
 
 TextureScaler::TextureScaler() {
 }
 
+bool TextureScaler::IsEmptyOrFlat(u32* data, int pixels, GLenum fmt) {
+	int pixelsPerWord = (fmt == GL_UNSIGNED_BYTE) ? 1 : 2;
+	int ref = data[0];
+	for(int i=0; i<pixels/pixelsPerWord; ++i) {
+		if(data[i]!=ref) return false;
+	}
+	return true;
+}
+
 void TextureScaler::Scale(u32* &data, GLenum &dstFmt, int &width, int &height, int factor) {
+	// prevent processing empty or flat textures (this happens a lot in some games)
+	// doesn't hurt the standard case, will be very quick for textures with actual texture
+	if(IsEmptyOrFlat(data, width*height, dstFmt)) {
+		INFO_LOG(G3D, "TextureScaler: early exit -- empty/flat texture");
+		return;
+	}
+
 	#ifdef SCALING_MEASURE_TIME
 	double t_start = real_time_now();
 	#endif