Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

Chapter 127 Determine the identity
But even with fingerprints, identification analysis is still very difficult.

A third of the prints from the same finger, blurred edges, ridges squeezed together by pressure.

It looks like five different fingerprints. This is the most difficult fingerprint Lu Chuan has encountered so far.

This time, using simple digit-map transformation and graph-number transformation can no longer preprocess fingerprints well.

Therefore, Lu Chuan adopted a method combining the spatial domain algorithm and the frequency domain algorithm.

In the image enhancement technology, the frequency domain algorithm is a two-dimensional digital processing of the image, which converts the image from the three-dimensional visible to the two-dimensional digital.

The techniques used here are mainly basic methods such as Fourier transform.

Then, through low-pass filtering, high-frequency signals are filtered out, leaving only low-frequency signals, so that noise interference in the image can be removed.

At the same time, high-pass filtering should be used to remove low-frequency signals, because the frequency will gradually increase when the image starts from the center point and spreads to the edge.

When reaching the very edge, the image frequency is the highest, and it is also the place where the edge is the most blurred.

High-pass filtering kicks out low-frequency signal effects, improving clarity around the edges.

Combining the two, the processing of the airspace algorithm has achieved certain results.

However, because the image itself is too blurry, the obtained image is not enough for subsequent matching only through the processing of the frequency domain algorithm.

After half an hour of processing, Lu Chuan continued to process the fingerprint image with an airspace algorithm.

The so-called frequency domain algorithm used by Lu Chuan is to operate on the gray value of the image.

This technology is divided into two types: point operation and neighborhood enhancement operation.

First, Lu Chuan used the point calculation algorithm to correct, transform and correct the gray scale.

The purpose of this operation is to make the image uniform, or to expand the dynamic range of the image and expand the contrast.

After that, Lu Chuan uses the neighborhood enhancement algorithm to smooth or sharpen the image.

Many high-end mobile phones currently on the market actually have functions such as sharpening and grayscale adjustment.

But compared with Lu Chuan's processing on the computer and using professional PS payment software, it's as big a difference as singing downstairs and shooting upstairs.

The two are not of the same order of magnitude.

Lu Chuan has to go through this process for every fingerprint.

On average, the processing time for a fingerprint is almost an hour.

However, even so, after Lu Chuan finished processing, he still couldn't use the full matching function of the fingerprint system.

Because the number of labels of feature points is not enough.

The judicial effectiveness of fingerprint identification is related to the proficiency in feature point matching in the process of fingerprint identification analysis, and it is an absolute relationship.

If there are less than thirteen marked points identified as the same, the fingerprint identification analysis has no legal effect.

Of course, in this case, it does not mean that fingerprint identification analysis is useless.

Because as long as there is no clear similarity and difference, the identity of the suspect can be actually supported.

As long as the identity of the other party is determined, even if there is no fingerprint evidence, the police handling the case can always dig out other evidence.

As long as people can find them, everything else is easy to handle.

Open the fingerprint comparison system, the second common comparison method in the system used by Lu Chuan.

Similarity comparison.

Five fingerprints means that Lu Chuan has five chances.

The comparison of the first fingerprint was very unsuccessful.

The system directly gives the failed comparison.

This means that this fingerprint and all the fingerprints in the system have similarities and differences, which means that the comparison fails.

The second fingerprint still failed.

In front of the computer, Lu Chuan was not discouraged. If even advanced fingerprint identification and analysis skills can't handle this fingerprint, then there are probably not many people in the country who can handle this fingerprint.

The third fingerprint comparison...failed again.

Looking at the last two fingerprints that had been preprocessed, Lu Chuan took a deep breath.

Even if the five comparisons are unsuccessful, it does not mean that there is no other party's information in the fingerprint database.

Because these five fingerprints were too incomplete, after Lu Chuan pre-processed, the resulting fingerprints were quite different.

Therefore, if it is unsuccessful, Lu Chuan has made plans to preprocess the original fingerprints again.

While thinking, the data of the fourth fingerprint was also entered into the system.

The light blue aperture slowly rotates in the center of the screen, and the system data has begun to match.

Drop drop drop.

Different from the perfectly matching "ding" sound, this time the system gives a continuous beep sound.

Lu Chuan lifted his spirits and looked at the screen carefully.

Similarity matching succeeded.

In the list, there are 28 fingerprints lying there quietly, waiting for Lu Chuan to appreciate them one by one.

"it is good!"

Lu Chuan clapped his palms together, feeling very excited.

Fingerprint identification analysis requires both technology and sometimes luck.

Or feel.

Having done so many fingerprint identification and analysis, Lu Chuan is very clear that the first impression of fingerprint preprocessing is very important.

If the fingerprints processed for the first time are not successfully matched, the further the process goes, the greater the distortion of the processing, and the less likely it is to succeed in the comparison.

Of course, this does not mean that the comparison must be unsuccessful.

Kung fu is not afraid of those who have a heart, no matter how thick the iron pestle is, it will become thinner if it rubs too much.

No matter how bad it is, you can rub it and spit it out.

28 similar fingerprints are sorted by the system according to the number of similar feature points.

Of course, this does not mean that the target fingerprint must be ranked first, and it may also be the one ranked last.

The key is that the original fingerprint is too severely damaged, only one-third the size, and blurred into an extremely distorted state.

Taking a deep breath, Lu Chuan started manual verification from the first fingerprint.

This time, Lu Chuan did not just check with the preprocessed fingerprints.

The most important thing is to check it with the original fingerprint.

This is the difficulty of manually checking fingerprints. No matter how rubbish the original fingerprints are, the criminal police have to sort out and compare them line by line.

Until obvious similarities and differences are found, it is judged that the comparison fails.

Or have not found similarities and differences, to determine the same.

28 fingerprints, the first fingerprint has a high degree of similarity, but it is also easy to find similarities and differences.

In less than 5 minutes, Lu Chuan discovered two obvious similarities and differences.

After marking, this fingerprint is goodbye.

Then there was the second fingerprint. Lu Chuan followed the lines in the middle, sorted it out one by one, and compared it with the original fingerprint.

This time the time was shorter, and the battle was over in 3 minutes.

The third fingerprint...

2 minutes.

Then the fourth, fifth...

Just like a beauty pageant in a club, more than [-] predestined female Bodhisattvas stand in a row, but whoever can purify the lonely soul of the guests can't listen to the manager's introduction.

Listening to his introduction, all of them have boundless mana.

At this time, you should get rid of all distracting thoughts, start from the beginning, pick one by one, and look at them one by one.

Is the hair what you like? Is the advantage outstanding enough? Is the eyes what you like? Is the skirt slit in place...

Click!

Lu Chuan, who had already compared No.19 fingerprints, seemed to be struck by lightning in his mind.

His eyes brightened, and his mind cleared up.

That means that fate has arrived, and it is you!
No. 19 fingerprints, Lu Chuan stroked them in place from the beginning, and compared the entire third of the fingerprints, and found no obvious similarities and differences.

Of course, this does not mean that the owner of this fingerprint must be the murderer.

After all, in a fingerprint, there is a one-third possibility of being the same as other people.

Although this probability is very small, if there is, there is, and this cannot be used as judicial evidence to sue the other party.

But in reality, one-third of the fingerprints can basically determine the identity of the other party.

And as long as it is confirmed, it will be easy to find other evidence.

(End of this chapter)