Once uploaded in SharinPix, images are always available for download.

You can even ask to download the original file, a transformed version (cropped, rotated) with or without annotation.

Here are the different options to download images from SharinPix : 

• Right click on image download is not working
• Download icon is available by configuration : Large View toolbar Download 
  For that you have to set the image_download ability to true : SharinPix Abilities 
  This could be done in the VF code page, in the controller code or even globally at the org from the SharinPix settings 
• Customizable Download link/button you can add as footer to your VF page : Image Large View Interaction with Footer 
• ZIP download from image selection (require Premium license)