detect square (diagonal) banners, and give a small margin of error

stepmania/src/BannerCache.cpp

@@ -10,6 +10,7 @@
 #include "RageUtil.h"
 #include "RageLog.h"
 #include "BannerCache.h"
+#include "CroppedSprite.h"
 #include "PrefsManager.h"
 #include "SDL_utils.h"
 #include "SDL_dither.h"
@@ -304,7 +305,7 @@ void BannerCache::CacheBannerInternal( CString BannerPath )
 
 	bool WasRotatedBanner = false;
 
-	if( img->w == img->h )
+	if( CroppedSprite::IsDiagonalBanner(img->w , img->h) )
 	{
 		/* Ack.  It's a diagonal banner.  Problem: if we resize a diagonal banner, we
 		 * get ugly checker patterns.  We need to un-rotate it.

stepmania/src/CroppedSprite.cpp

@@ -56,7 +56,7 @@ void CroppedSprite::CropToSize( float fWidth, float fHeight )
 	float fOriginalX = GetX();
 	float fOriginalY = GetY();
 
-	if( iSourceWidth == iSourceHeight )		// this is a SSR/DWI CroppedSprite
+	if( IsDiagonalBanner(iSourceWidth, iSourceHeight) )		// this is a SSR/DWI CroppedSprite
 	{
 		float fCustomImageCoords[8] = {
 			0.02f,	0.78f,	// top left
@@ -137,3 +137,10 @@ void CroppedSprite::CropToSize( float fWidth, float fHeight )
 	// restore original XY
 	SetXY( fOriginalX, fOriginalY );
 }
+
+bool CroppedSprite::IsDiagonalBanner( int iWidth, int iHeight )
+{
+	/* A diagonal banner is a square.  Give a couple pixels of leeway. */
+	return iWidth >= 100 && abs(iWidth - iHeight) < 2;
+}
+

stepmania/src/CroppedSprite.h

@@ -25,6 +25,8 @@ public:
 	void SetCroppedSize( float fWidth, float fHeight );
 	void SetWH(float fWidth, float fHeight);	
 
+	static bool IsDiagonalBanner( int iWidth, int iHeight );
+
 protected:
 	void CropToSize( float fWidth, float fHeight );
 

stepmania/src/Song.cpp

@@ -27,6 +27,7 @@
 #include "FontCharAliases.h"
 #include "TitleSubstitution.h"
 #include "BannerCache.h"
+#include "CroppedSprite.h"
 
 #include "NotesLoaderSM.h"
 #include "NotesLoaderDWI.h"
@@ -670,6 +671,13 @@ void Song::TidyUpData()
 			m_sBackgroundFile = arrayImages[i];
 			continue;
 		}
+
+		if( CroppedSprite::IsDiagonalBanner(width, height) )
+		{
+			m_sBannerFile = arrayImages[i];
+			continue;
+		}
+
 		if( !HasBanner()  &&  100<=width  &&  width<=320  &&  50<=height  &&  height<=240 )
 		{
 			m_sBannerFile = arrayImages[i];