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Fine Image Comparison

Fine image comparison is a specialized technology especially pertinent to media intelligence applications such as advertising identification. It allows to esealy compare 2 images in order to point the differences.

Fine image comparison is designed

  • To automate the comparison of images which match but which may contain difference
  • To provide additional details on the results of matches. The fine image comparison feature provides visual feedback about matched images including a visual highlight showing where differences are located.

The Fine Image Comparison process generates these elements:

  • score: a score is generated which quantifies the visual distance between the two images
  • visual indicators: two analytical images are generated for each fine comparison effected. These analytical images indicate the zones within the images in which there are variations.

A LTU API is available to let you fine compare two images.


  • image1 : buffer image or URL
  • image2 : buffer image or URL

The APIS returns a Json result containing 2 images with the score

Here a curl example:

curl -d 'image1=' -d 'image2=' -X POST '''

Example of result :

  "content": {
    "query_image": "/9j/4AAQSkZJRgABAQAAAQABAAD/…”,
    "ref_image": "/9j/4AAQSkZJRgABAQAAAQABAAD/…”,
    "score": 1.4694126844406128
  "code": "0",
  "message": "ok"

3.1. Industry

Let's compare integrated electronic circuit: After machining, the operator makes an acquisition of his newly manufactured piece.


The images acquisition is made in a controlled environment: constant brightness and fixed camera axis. The acquisition must be done in conditions similar to the reference image for better veracity of the results

The differences are very thin:

  • central point: a 2mm component is not present on the image of the operator
  • top point in the middle: fine stripe on the image of the operator
  • the other difference are artefact.

3.2. Prospectus

The examples below are typical of the types of images to which Fine Image Comparison is applied:

These two images are identical, except for the pricing details in the lower part of the image. The whitened zones in the image at right indicate the zones in which differences are detected.

The differences between these two images are highlighted in the upper left corner.

In a media intelligence application, Fine Image Comparison is typcially used in conjunction with LTU image matching.

  • Unidentified advertisements are compared with a database of know advertisements.
  • Certain ads are identified as definite matches.
  • Other ads are identified as possible matches, but which need validation (their matching scores may indicate the possibility of variations)
  • Fine Image Comparison is applied to the pairs of possible matches. The score generated by Fine Image Comparison determines whether the possible matches should be classified as definite matches or should be examined in a human validation process.