Enhance contrast for very low contrast images. This adjustment prevents

the frames from being displayed as all-white, which is a visually unpleasant artifact commonly encountered in very dark frames without visible stars. By slightly increasing the maximum value when the difference between min and max values is minimal, we improve the visibility of image details while avoiding the all-white display issue. Signed-off-by: Leo Shatz <[email protected]>
OpenPHDGuiding · Jan 26, 2024 · 18d5e03 · 18d5e03
1 parent 4030ca7
commit 18d5e03
Showing 1 changed file with 9 additions and 0 deletions.
diff --git a/guider.cpp b/guider.cpp
@@ -441,6 +441,15 @@ bool Guider::PaintHelper(wxAutoBufferedPaintDCBase& dc, wxMemoryDC& memDC)
         {
             int blevel = m_pCurrentImage->FiltMin;
             int wlevel = m_pCurrentImage->FiltMax;
+
+            // Enhance contrast for very low contrast images. This adjustment prevents the frames
+            // from being displayed as all-white, which is a visually unpleasant artifact commonly
+            // encountered in dark frames. By slightly increasing the maximum value
+            // when the difference between min and max values is minimal, we improve the visibility
+            // of image details while avoiding the all-white display issue.
+            if (wlevel < 4096 && (wlevel - blevel) < 16)
+                wlevel += 16;
+
             m_pCurrentImage->CopyToImage(&m_displayedImage, blevel, wlevel, pFrame->Stretch_gamma);
         }