Knowledgebase

Interpreting Results

Image Analyzer ViS supports the classification of images for multiple threat categories. The scan results return a probability for each active category.

For example, if the categories Porn, Terrorism, and Weapons are activated, then a single image will return a probability for each category.

scan results: 

{ 
Porn : 0.2433

Terrorism : 99.67

Weapons : 89.486

} 

The result returned is 0-100 and indicates the probability the image contains visual attributes common to the category. It is possible for an image to return high probabilities for multiple categories; in this example the image is of a terrorist holding a firearm and therefore returns high positive results for both Terrorism and Weapons categories.

Setting Thresholds

The higher the probability for a particular category the more likely the image composition matches that category. The default recommended threshold is 50%, this will provide high detection with false positives of approximately 1-2%. Increasing the threshold will decrease the false positives and detection rate. Lowering the threshold will increase the false positives and detection rate.

The table below provides a guideline for the level of false positive/detection rates at certain thresholds for the porn category.

Threshold Value	99%	95%	75%	50%	25%	5%	1%
False Positive Rate*	0.09%	0.20%	0.61%	1.67%	4.43%	9.40%	19.35%
Detection Rate*	67.66%	78.69%	87.08%	92.77%	97.00%	98.29%	99.30%

* Figures are indicative and will vary depending on image data and category. Dataset used to produce these figures was designed to challenge the technology.

If images that return a probability equal to or greater than 25% are considered pornographic then the detection rate will be approximately 97% with 4% false positives.

If images that return a probability equal to or greater than 75% are considered pornographic then the detection rate will be approximately 87% with 0.6% false positives.

Setting the optimum threshold will depend on the use case and the desired goal. It is recommended to start with a threshold of 50% and increase/decrease it as required.

 

 

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