your are missing .aspx
in the URL:
https://localhost/getattachment/about/vp_megamenu_feat_packaginganalysis.jpg.aspx?width=450&height=510&ext=.jpg
How exactly do you get this URL? Normally if you get them in transformation you use these methods
Your files might be stored as binary in the DB, because of your settings.
select * from CMS_Attachment where attachmentname = 'vp_megamenu_feat_packaginganalysis.jpg'
If it settings were set to file system, then whiout workflows your files should ~/<site code name>/files
. Here is the documentation