2 files changed, 15 insertions, 0 deletions
diff --git a/rfb/ScaledPixelBuffer.cxx b/rfb/ScaledPixelBuffer.cxx
index 8e7430b4..b566ea4e 100644
--- a/rfb/ScaledPixelBuffer.cxx
+++ b/rfb/ScaledPixelBuffer.cxx
@@ -140,6 +140,17 @@ void ScaledPixelBuffer::scaleRect(const Rect& r) {
   }
 }
 
+Rect ScaledPixelBuffer::calculateScaleBoundary(const Rect& r) {
+  static int x_start, y_start, x_end, y_end;
+  x_start = r.tl.x == 0 ? 0 : ceil((r.tl.x-1) * scale_ratio);
+  y_start = r.tl.y == 0 ? 0 : ceil((r.tl.y-1) * scale_ratio);
+  x_end = ceil(r.br.x * scale_ratio - 1); 
+  x_end = x_end < scaled_width ? x_end + 1 : scaled_width;
+  y_end = ceil(r.br.y * scale_ratio - 1);
+  y_end = y_end < scaled_height ? y_end + 1 : scaled_height;
+  return Rect(x_start, y_start, x_end, y_end);
+}
+
 void ScaledPixelBuffer::recreateScaledBuffer() {
   if (scaled_data) delete [] scaled_data;
   scaled_data = new U8[scaled_width * scaled_height * (bpp / 8)];
diff --git a/rfb/ScaledPixelBuffer.h b/rfb/ScaledPixelBuffer.h
index b4b5a8ec..8342a583 100644
--- a/rfb/ScaledPixelBuffer.h
+++ b/rfb/ScaledPixelBuffer.h
@@ -68,6 +68,10 @@ namespace rfb {
     // using bilinear interpolation
     virtual void scaleRect(const Rect& r);
 
+    // Calculate the scaled image rectangle which depend on the source 
+    // image rectangle.
+    inline Rect calculateScaleBoundary(const Rect& r);
+
   protected:
     virtual void recreateScaledBuffer();