gui: Simplify and rework EmbeddedImage class

The wxImage Scale/Rescale methods with wxIMAGE_QUALITY_HIGH upsamples
and downsamples using the bicubic and box resampling methods
respectively, so let's just use that instead of the ResampleBox method,
which is undocumentated and probably shouldn't be used.

The Rescale function also modified the image when it was not supposed
to. Fix it, and rename it scale to avoid confusion with the wxWidgets
class.

pcsx2/gui/Resources/EmbeddedImage.h

@@ -26,8 +26,7 @@ class IEmbeddedImage
 {
 public:
 	virtual const wxImage& Get()=0;
-	virtual wxImage Rescale( int width, int height )=0;
+	virtual wxImage Scale( int width, int height )=0;
-	virtual wxImage Resample( int width, int height )=0;
 };
 
 //////////////////////////////////////////////////////////////////////////////////////////
@@ -59,7 +58,7 @@ protected:
 			m_Image.LoadFile( joe, ImageType::GetFormat() );
 
 			if( m_ResampleTo.IsFullySpecified() && ( m_ResampleTo.GetWidth() != m_Image.GetWidth() || m_ResampleTo.GetHeight() != m_Image.GetHeight() ) )
-				m_Image = m_Image.ResampleBox( m_ResampleTo.GetWidth(), m_ResampleTo.GetHeight() );
+				m_Image.Rescale( m_ResampleTo.GetWidth(), m_ResampleTo.GetHeight(), wxIMAGE_QUALITY_HIGH );
 		}
 	}
 
@@ -107,31 +106,15 @@ public:
 
 	// ------------------------------------------------------------------------
 	// Performs a pixel resize of the loaded image and returns a new image handle (EmbeddedImage
-	// is left unmodified).  Useful for creating ugly versions of otherwise nice graphics.  Do
+	// is left unmodified).
-	// us all a favor and use Resample() instead.
 	//
-	// (this method included for sake of completeness only).
-	//
-	wxImage Rescale( int width, int height )
-	{
-		_loadImage();
-		if( width != m_Image.GetWidth() || height != m_Image.GetHeight() )
-			return m_Image.Rescale( width, height );
-		else
-			return m_Image;
-	}
 
-	// ------------------------------------------------------------------------
+	wxImage Scale( int width, int height )
-	// Implementation Note: This function uses wxWidgets ResampleBox method to resize the image.
-	// wxWidgets ResampleBicubic appears to be buggy and produces fairly poor results when down-
-	// sampling images (basically resembles a pixel resize).  ResampleBox produces much cleaner
-	// results.
-	//
-	wxImage Resample( int width, int height )
 	{
 		_loadImage();
+		// Not strictly necessary - wxWidgets does the dimensions check anyway.
 		if( width != m_Image.GetWidth() || height != m_Image.GetHeight() )
-			return m_Image.ResampleBox( width, height );
+			return m_Image.Scale( width, height, wxIMAGE_QUALITY_HIGH );
 		else
 			return m_Image;
 	}