diff --git a/src/zm_image.cpp b/src/zm_image.cpp
index 1835d59b4..3675f78a5 100644
--- a/src/zm_image.cpp
+++ b/src/zm_image.cpp
@@ -312,12 +312,27 @@ void Image::Blend( const Image &image, int transparency ) const
 {
 	assert( width == image.width && height == image.height && colours == image.colours );
 
+	if ( !blend_buffer )
+	{
+		blend_buffer = new unsigned int[size];
+
+		unsigned int *pb = blend_buffer;
+		JSAMPLE *p = buffer;
+		
+		while( p < (buffer+size) )
+		{
+			*pb++ = (unsigned int)((*p++)<<8);
+		}
+	}
+
 	JSAMPLE *psrc = image.buffer;
 	JSAMPLE *pdest = buffer;
+	unsigned int *pblend = blend_buffer;
 
 	while( pdest < (buffer+size) )
 	{
-		*pdest++ = (JSAMPLE)(((*pdest * (100-transparency))+(*psrc++ * transparency))/100);
+		*pblend = (unsigned int)(((*pblend * (100-transparency))+(((*psrc++)<<8) * transparency))/100);
+		*pdest++ = (JSAMPLE)((*pblend++)>>8);
 	}
 }
 
diff --git a/src/zm_image.h b/src/zm_image.h
index 2f2810166..28beae295 100644
--- a/src/zm_image.h
+++ b/src/zm_image.h
@@ -61,11 +61,15 @@ protected:
 	JSAMPLE *buffer;
 	bool our_buffer;
 
+protected:
+	mutable unsigned int *blend_buffer;
+
 public:
 	Image( const char *filename )
 	{
 		ReadJpeg( filename );
 		our_buffer = true;
+		blend_buffer = 0;
 	}
 	Image( int p_width, int p_height, int p_colours, JSAMPLE *p_buffer=0 )
 	{
@@ -84,6 +88,7 @@ public:
 			our_buffer = false;
 			buffer = p_buffer;
 		}
+		blend_buffer = 0;
 	}
 	Image( const Image &p_image )
 	{
@@ -94,6 +99,7 @@ public:
 		buffer = new JSAMPLE[size];
 		memcpy( buffer, p_image.buffer, size );
 		our_buffer = true;
+		blend_buffer = 0;
 	}
 	~Image()
 	{
@@ -101,6 +107,7 @@ public:
 		{
 			delete[] buffer;
 		}
+		delete[] blend_buffer;
 	}
 
 	inline int Width() { return( width ); }