Add NoUpscale option

cmd/cbconvert-gui/options.go

@@ -25,6 +25,7 @@ func options() cbconvert.Options {
 	opts.Height = iup.GetHandle("Height").GetInt("VALUE")
 	opts.DPI = dpiValue(iup.GetHandle("DPI").GetAttribute("VALUE"))
 	opts.Fit = iup.GetHandle("Fit").GetAttribute("VALUE") == "ON"
+	opts.NoUpscale = iup.GetHandle("NoUpscale").GetAttribute("VALUE") == "ON"
 	opts.Filter = iup.GetHandle("Filter").GetInt("VALUE") - 1
 	opts.Quality = iup.GetHandle("Quality").GetInt("VALUE")
 	switch opts.Format {

cmd/cbconvert-gui/settings.go

@@ -39,6 +39,7 @@ var settings = []setting{
 	{"NoNonImage", kindBool, "OFF"},
 	{"Combine", kindBool, "OFF"},
 	{"Fit", kindBool, "OFF"},
+	{"NoUpscale", kindBool, "OFF"},
 	{"Lossless", kindBool, "OFF"},
 	{"Grayscale", kindBool, "OFF"},
 	{"OutDir", kindStr, ""},

cmd/cbconvert-gui/widgets.go

@@ -359,6 +359,8 @@ func tabImage() iup.Ihandle {
 			iup.Vbox(
 				iup.Toggle(" Best Fit").SetHandle("Fit").
 					SetAttributes(`TIP="Best fit for required width and height"`),
+				iup.Toggle(" No Upscale").SetHandle("NoUpscale").
+					SetAttribute("TIP", "Do not enlarge images already smaller than the requested size"),
 			),
 			iup.Vbox(
 				iup.Label("Resize Filter:"),