How Reverse Image Search Technology & Algorithms Work

Browsing for reverse photos using automated tools is handy. It provides you similar images and finds duplicate ones in return for your query. It is the technology that encourages search engines to adopt computer vision. Every progress in this field provides a way for some exciting product features.

To build a reverse image search system, we first need a way to find the meaning of image data. For computers, the picture is a 3-D matrix consisting of hundreds of thousands of numbers. It represents the red-green pixel value (RGB).

But for humans, a picture is setting the semantic pattern – lines, curves, gradients, textures, and colors – all of which are integrated into some meaningful ideas. But how do search engines compare photos? Well, this is interesting, and it’s not so easy to answer such questions.

Reverse Image Search

Reverse image search algorithm research

Reverse photos search technology is about image processing and classification algorithms. So there are many variant approaches for this, and this is unknown which the search engine currently uses. I can only mention here the system that is most likely to use by reverse image search technology:

  • Filter

Features SIFT (scale-invariant feature transform) are perfect for recognizing similar images. They are consistent for size and location.

  • Surf

Surf (speed up powerful features) accelerates SIFT technology by replacing the Gaussian SIFT filter. Reverse photos search engines can work on keywords as well. But sometimes you only need to know where an image comes from, regardless of how many words it is worth it. For this reason, there are reverse image search engines provided by people.

Because you don’t give words on your request, how do they get the command of what to look for? And, also, how do they find it? How every search for an image varies among multiple browsing apps? They keep the algorithms right below it, but basic ideas are out there and are not so difficult to understand.

Latest Reverse image Search Applications or Online Tools

Multiple online tools are using reverse photo search technology. But we recommend ReverseImageSearch because it’s the most accurate, fastest, and safe reverse image search utility available online. Moreover, it’s free and very easy to use. Let’s say we want to analyze the “image”, We simply upload the photo in this tool and find similar within seconds.

Fingerprint and Pictures

The actual reverse photos may be unique to human fingerprints. Because the opportunity for two images containing the exact pixel settings is unimaginable infinitesimal. While the chances of fingerprint collisions are around 64 billion – relatively good options.

But how do you describe pictures? The steps differentiate depending on the algorithm, but most of them follow the same basic formula. First, you have to measure the features of different image pieces. And even things like Fourier’s transformation, the method breaks the image into the sinus and cosine.

Neural Network – A feature extractor

Classifier Neural Network reverse photos work through image conversion which is a point in the high dimensional pixel space to “Low-dimension” feature vector “represents the characteristics of” features “studied by the network.

We can then take trained neural networks, removing the last high-level layer. Which was initially used to classify objects, and using the model dissected to change our photos into a vector feature.

Metric similarity: Cosine similarity

After converting our images to display vectors, we then need several types of metrics in common to compare them. One of these candidates, and used in this example, is “cosine similarity”. It measures the “angle” between images in the high dimension feature room.

It is illustrated in a very simplified version below for two-dimensional feature space, comparing the similarity of cosine between the input reverse photos and “A” / “B” picture. We are here seeing that “A” contains similar objects as input pictures and hence the “angle” smaller among them, while “B” includes things that look different and have a larger angle.

Picture Clustering

By processing reverse photos in our database through our “feature extraction model”, we can convert all photos to feature vector representations. It means we now have quantitative descriptions in terms of image content.

Pass these vectors through clustering algorithms. Which will specify pictures to various groups based on their content. In doing this, we still don’t know what contains individual photos. But we know that pictures in different groups usually have similar objects/content. 


Reverse photos search is the best way to run your query for finding pictures. But one may be confused about how it actually works. Here we have explained all. The reverse image search engine is easy to use but it requires a lot of effort to make such tools and make them process accordingly.

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