complete unbound the zoom... previously allowed 10% - 1600%

now it's limited to as small as possible and zoomed in as long as the image "rescaled" is < 65535 (internal limitation)

While not very useful for most people, for those using extremely large or small images, it gives them more options

Partially addresses #85

src/JPEGView/Helpers.h

@@ -82,8 +82,8 @@ namespace Helpers {
 	};
 
 	// Maximum and minimum allowed zoom factors for images
-	const double ZoomMax = 16.0;
-	const double ZoomMin = 0.1;
+	const double ZoomMax = DBL_MAX; // unbound the maximum zoom, previously set at 16.0 (1600%)
+	const double ZoomMin = DBL_MIN; // unbound the minimum zoom, previously set at 0.1 (10%)
 
 	// Round to integer
 	inline int RoundToInt(double d) {

src/JPEGView/MainDlg.cpp

@@ -2622,6 +2622,14 @@ void CMainDlg::PerformZoom(double dValue, bool bExponent, bool bZoomToMouse, boo
 		nNewYSize = (int)(m_pCurrentImage->OrigHeight() * m_dZoom + 0.5);
 	}
 
+	// because we've increased the maximum zoom allowed, only actually perform the zoom if the old and new dimensions differ
+	// the float arithmetic doesn't always come up with the same answer
+	if (nOldXSize == nNewXSize && nOldYSize == nNewYSize) {
+		m_dZoom = dOldZoom;  // restore previous zoom value, then do nothing
+		return;
+	}
+
+
 	if (bZoomToMouse) {
 		// zoom to mouse
 		int nCenterX = m_bZoomMode ? m_nCapturedX : m_nMouseX;