Image Histogram allows you to quickly view the image histogram for images on the web. 

To use, simply right-click on an image and choose "Toggle Histogram," and the image histogram will be overlaid on the image. To go back to your original image, simply choose "Toggle Histogram" again. 

Separate Red, Green, and Blue channel histograms can also be shown. To switch between color and normal histograms, click the histogram icon in the in the browser bar, or go to the Image Histogram Options from the Chrome Extensions page. 

New in version 0.1.8: Fixes for 500px.com's site redesign
New in version 0.1.2: Bug fixes, options page reorganized.
New in Version 0.1.1: Added: a browser icon for toggling between color and normal histograms, along with options to use a "smart" histogram color filter, and the ability to show the color histogram as either three graphs separated vertically, or all in one. 
New in Version 0.0.11: Color Histograms! 
New in Version 0.0.10: Work around several problem scenarios where the histogram wouldn't show up. 
New in Version 0.0.7: 500px photo page support!
New in Version 0.0.6: Flickr photo page and lightbox support! 

In some cases where the page author is preventing right-click by putting another element above the image, the histogram won't work. 

A note about permissions: In order to access the image data needed to compute the histogram, this extension needs your permission to access data on webpages you visit. It only accesses image data, and only then when you select the "Toggle Histogram" action. It neither sends or receives additional external data.