Fixed frame selection for pictures

src/Gifitti/Gifitti/View_Models/MainForm.cs

@@ -118,7 +118,7 @@ namespace Gifitti.View_Models
                 path = folderBrowserDialog.SelectedPath;
 
 
-            for (int i = 0; i < gm.numberOfFrames; i++)
+            for (int i = gm.startFrame; i < gm.endFrame; i++)
             {
                 var a = gm.GetFrame(i);
                 a.Save(path + @"\frame" + i + @"." + IMAGE_TO_EXTENSION[format], format);