Social media keeps getting more visual, and for evidence of that, look no further than Clorox Co.'s Hidden Valley Ranch. One recent Twitter post of a photo that showed chicken wings and French Fries with Hidden Valley Ranch dressing generated 150 million retweets and an ultimate audience of nearly 44 million people, according to Brian Kim, director of product management for ad-tech startup GumGum.

The problem for brands is that much of such visual social-media activity is invisible to them.

"Nearly 60% of all digital impressions are now driven by images," Mr. Kim said in a presentation last month at Innovation Xchange, a program by Cincinnati based Cintrifuse, a venture "fund of funds" that includes money and guidance from Procter & Gamble Co.. The event brought brand marketers and startups together for speed-dating sessions.

"For brand marketers on social media, images can be a big problem," Mr. Kim said. "We found through our studies that nearly 85% of posts that contain a logo contain either no text or no text that's relevant to your brand."

So what goes on in visual social media largely eludes the tracking and analytics brands use to keep tabs on what people are saying -- or seeing about them.

That's where Mantii, a new social-media analytics platform used by Clorox Co., comes in. It's an offshoot of GumGum, a Santa Monica, Calif.-based startup that originally focused on creating an "in-image ad platform" that overlays rich-media ads in images on publisher sites -- such as a campaign last year for L'Oreal's Ombre hair-color brand that targeted ads to run atop photos based on the hair color of the women in them.

In the case of Hidden Valley Ranch, Mantii found about half of all social-media posts about the brand are showing or talking about chicken fingers and fries, Mr. Kim said. That comes as millennials in much of the country have begun swapping ketchup for ranch dressing.

Mary O'Connell, senior director-global digital marketing, social media and public relations at Clorox, confirmed the company was "in the early stages" of using GumGum for social-media analytics.

Using the same GumGum technology that crawls the web looking for images to pair with ads, Mantii looks for all or part of brand logos contained in social-media posts, whether they mention the brand in text or not.

Mantii then classifies, stores and saves the data for reporting in dashboards brands can use. The database, to the extent possible, also gathers and applies demographic information such as age, gender and location along with topic views, affinities with other brands and interests, and sentiment analysis among users of Facebook, Instagram and Twitter.

"We can drill into a specific user, understand how they're talking about a specific product, understand their affinities, that they're probably male, and what their other interests are," Mr. Kim said. That gives brands a visual dimension to find spikes in buzz caused by their social-media campaigns or other efforts.