The below links has various image processing functionality implemented using Javascript. They can be useful to implement various image processing functionality in website frontend.

www.marvinj.org/en/index.html

gitHub.com/inspirit/jsfeat
Some features of this library are

• Basic image processing methods (grayscale, derivatives, box-blur, resample, etc.)
• Grayscale
• Box blur
• Gaussian blur
• Equalize histogram
• Fast Corners feature detector
• YAPE06 feature detector
• YAPE feature detector
• ORB feature descriptor
• HAAR object detector
• BBF object detector