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Cloud Face Recognition for Cellular Functions: Analysis | by Elena Stepanova | Nov, 2020


Elena Stepanova

Outcomes from Implementing 5 Finest Face Recognition APIs

Within the earlier chapters of this sequence we’ve mentioned a number of cloud face recognition companies and designed a prototype app. Now it’s time to check the chosen suppliers and consider their efficiency.

If you’re inquisitive about different elements of the sequence, verify these out:

Part 1: Overview of some popular face recognition services

Part 2: Implementation example in Android

Part 3: Results and performance of chosen face recognition providers

After we’ve been by design and implementation, it‘s time to reap the outcomes. For this objective my prototype has two modes: demo and check mode.

Demo mode

The demo mode has performance of a customer surveillance system and is used to indicate how totally different suppliers react to slight modifications within the look.

First, I registered myself throughout the AI service and the native database. Then I took a sequence of images, which a pal of mine known as “I killed my husband and went for a run”. The popularity outcomes had been as follows.

Generally cloud companies had been somewhat assured about the truth that me sporting glasses or lengthy hair remains to be the identical me. As anticipated, some modifications in look have led to decrease confidence ranges, nevertheless, they had been nonetheless negligible. Solely in case of Luxand, I might in all probability get away with the homicide simply sporting a hairdo and glasses.

Take a look at mode

Not like demo mode, the check mode is used to acquire and examine outcomes of assorted cloud service suppliers utilized to a check database.

In face recognition the efficiency of machine studying algorithms is normally measured by calculating helpful metrics, akin to

TP – true positives (appropriately recognised candidates)

TN – true negatives (appropriately rejected candidates)

FP – false positives (candidates that ought to not have been accepted)

FN – false negatives (rejected candidates that ought to have been accepted)

Then these values are used to calculate true adverse charge, which measures the proportion of precise negatives which might be appropriately recognized as such.

We will additionally estimate precision, recall (sensitivity, TPR) and accuracy of the face recognition companies.

Along with accuracy, which can provide deceptive outcomes for imbalanced knowledge units, it’s steered to calculate balanced accuracy, which makes use of the TPR and TNR as a substitute of absolute values.

The open supply database chosen for the implementation is Faces94 created by College of Essex. The pictures on this database had been captured from the identical distance whereas the topic was talking, in order that they signify numerous, however not excessive (like within the different Essex Database known as Grimace), face expressions. Furthermore, the picture format is supported by most of face recognition companies and the scale is taken into account as close to to optimum. Sadly, the photographs had been taken in a single session, so there isn’t any variation in such particulars as make up, equipment or coiffure, which could be very more likely to occur in actual life situations. Nonetheless, this database appears to be the only option for our prototype.

First, native and cloud databases are populated with 34 totally different faces from the College of Essex Face database. Afterwards, a random face is chosen, which might belong to both of these 34 registered individuals or to one among different 12 unknown individuals from the identical Essex Database. Then the chosen face is distributed for analysis to all 5 face recognition companies. Candidates from the returned arrays are matched in opposition to the native database and the popularity outcomes are merged collectively for each distinctive customer id. These knowledge is then written to a file, which accumulates the outcomes of 100 check runs.

The variety of optimistic or adverse outcomes will rely upon the set confidence threshold used to both settle for the candidate as “recognised” or to reject him. Subsequently the popularity companies are known as with a threshold set to 0.0, in order to get the boldness charges for all of the candidates and check the collected outcomes in opposition to each doable threshold charge. Assuming, recognisedId is the customer id returned by the face recognition service and trueId stands for the true customer id, all doable outcomes might be described as follows:

if (end result.confidence >= threshold) AND (recognisedId == trueId) => return TPif (end result.confidence >= threshold) AND (recognisedId != trueId) => return FPif (end result.confidence < threshold) AND (recognisedId != trueId) => return TNif (end result.confidence < threshold) AND (recognisedId == trueId) => return FN

I ran a Python script primarily based on these guidelines for numerous confidence threshold ranges to check the efficiency of all face recognition companies. Nonetheless, there have been some obstacles that made evaluations not as exact and full as desired.

To start with, the restriction on the variety of candidates returned. It differs in all companies, however essentially the most disappointing is Face++, which is barely 5 candidates most. Subsequently, to make comparability legitimate, it might be essential to set the identical most variety of returned candidates for each different service. This, nevertheless, limits the conclusions that may be made in regards to the outcomes and the efficiency of the companies. For instance, setting a better threshold will shield us from dropping true positives. However on the identical time, it will enhance the rejection charge and slight modifications in look could produce FN, when the consumer can be prompted with annoying “I couldn’t recognise you…” record of doable candidates.

One other consideration to be made is normalization of outcomes. From uncooked knowledge obtained from face recognition companies, it turns into apparent, that each one companies have totally different strategy to setting confidence ranges. The boldness degree returned for a similar adverse particular person can differ from 5% to 50%. Subsequently it’s essential to normalize the information earlier than evaluating totally different companies with one another. To do that, all the outcomes are grouped by suppliers and confidence values are normalised utilizing the next formulation:

Working simulations in Python for various normalized confidence threshold ranges throughout the vary from 0% to 100% with the step of 5%, has led to following outcomes.

Response instances

The quickest face recognition service turned out to be Kairos, which solely wants 598.19 ms on common. It’s intently adopted by Amazon with 677.63 ms. The Chinese language service supplier Face++ comes third with 794.77 ms. Probably the most shocking end result was proven by Microsoft, which requires 2764.01 ms, which is sort of 5 instances longer than Kairos’ response time! This slowness could have one thing to do with extra intricate logic and elaborate design that the API supplies. It may be seen that each companies which have the particular person characteristic, particularly Luxand and Microsoft, got here final within the response time competitors. Nonetheless, in contrast to different companies, they don’t simply return an array of faces, however attribute each face to a novel particular person, which is extra helpful in lots of use instances.

Confidence sensitivity

As we mentioned earlier than, every service treats confidence ranges in another way, which turns into extra clear from the next charts.

Apparently, there are “confident” and fewer “confident” companies. Whereas Amazon and Luxand are virtually 100% positive if they are saying they acknowledged an individual, Microsoft and Kairos might be 75%-100% positive. Face++ is extra like the primary two and attributes to all acknowledged individuals confidence greater than 90%.

Related conclusions might be made about confidence ranges, which companies attribute to their true adverse candidates. It’s apparent, that Microsoft, Amazon and Kairos are inclined to play protected and attribute to their true negatives decrease confidence ranges underneath 65%. As compared, the beginning confidence degree for Face++ true negatives is round 25% and goes as much as 80%. It means setting confidence threshold lower than 80% can produce false negatives with Face++, whereas for Microsoft, Amazon and Kairos this threshold is round 65%. Luxand reveals very unsatisfying ends in these phrases and appears to not distinguish faces very nicely, as a result of typically it thinks it might recognise an unknown or unsuitable particular person with confidences near 100%.

For that reason it was essential to make use of normalised confidence ranges, in order that companies might be in contrast by way of TNR, Recall, Precision and Accuracy.

True Destructive Fee

From the TNR chart it may be seen that that Amazon, Kairos and Microsoft behave very equally and, as anticipated from a great face recognition service, reject individuals with low confidence outcomes. Quite the opposite, Face++ reveals confidence ranges biased upwards. Luxand reacts to threshold modifications very regularly, which can signify that the service doesn’t distinguish between totally different faces very nicely.


Sensitivity, or recall, or TPR, is the extent to which precise positives should not missed (so false negatives are few) and measures the proportion of precise positives which might be appropriately recognized as such. The chart reveals that Kairos and Microsoft behave equally and begin rejecting true candidates early, whereas the opposite companies are inclined to overlook fewer true positives. As was talked about earlier than, Luxand and Face++ distinguish candidates worse, which implies they’ve extra probabilities of mistaking one particular person for one more, in order that they have much less false negatives, however on the identical time are inclined to have extra false positives as nicely.


Precision, or optimistic predictive worth reveals is how shut two or extra measurements are to one another. It may be seen, that Amazon, Kairos and Microsoft distinguish between false and true guests somewhat nicely. Face++ wants greater threshold to succeed in higher precision. As for Luxand, the outcomes appear to lack precision usually.


The accuracy and balanced accuracy graphs verify earlier observations: the upper the chosen confidence threshold, the extra correct are the outcomes. Nonetheless, Amazon, Kairos and Microsoft want decrease threshold to indicate correct outcomes. Amazon reveals excellent outcomes, each rejecting true negatives and figuring out true positives. Face++ reacts to the change in confidence threshold very strongly, which has to do with the truth that the dataset solely consists of 5 doable faces, that are recognised with upwards biased confidences. As for Luxand, its accuracy modifications very regularly with confidence thresholds, which might make it tough to seek out an applicable threshold, which might maximize the variety of true positives and reduce false negatives.

After this lengthy technique of evaluating 5 in style cloud face recognition companies, we are able to lastly decide our favourites. I might charge them within the following descending order: Amazon, Microsoft, Kairos, Face++, Luxand. It comes as no shock, that IT giants akin to Microsoft and Amazon have proven higher outcomes than smaller corporations. Nonetheless, Kairos additionally carried out fairly nicely, and the comparatively poor outcomes of Face++ might be attributed to the demographic specifics of this algorithms and the chosen database.

To sum up, this experiment proved the viability of face recognition purposes on mobiles units. Not so way back it was perceived, that though pc imaginative and prescient might already be extensively used to determine individuals, it was nonetheless removed from human imaginative and prescient. Nonetheless, the outcomes have proven that the scenario has modified and face recognition algorithms have improved loads.

It appears to be very seemingly that within the nearest future these algorithms will grow to be even higher and computer systems will change people in duties the place face recognition must be carried out. On this case cell units will grow to be a typical platform for face recognition purposes and because of cloud companies will be capable of profit from low latency and excessive efficiency of up-to-date face recognition algorithms.

I hope this text will encourage you to make use of face recognition in your cell apps, which is a superb contactless various to conventional technique of identification.


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