But even with fingerprints, identification and analysis are still very difficult. A third of the fingerprints left by the same finger have blurred edges, and the pressure-induced ridge lines are squeezed together.

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

This time, the simple number and number transformation of the number of images can no longer be used to preprocess the fingerprint.

Therefore, Lu Chuan adopts a combination of spatial algorithm and frequency domain algorithm. In image enhancement technology, the frequency domain algorithm is a two-dimensional processing of the digitization of the image, which digitizes the image from the three-dimensional visible concrete into a two-dimensional number.

The techniques used here are mainly basic methods such as the Fourier transform. Then, through low-pass filtering, the high-frequency signal is filtered out, leaving only the low-frequency signal, so that the noise interference in the image can be removed.

At the same time, high-pass filtering is used to remove low-frequency signals, because the frequency of the image increases gradually as it spreads from the center point to the edges.

When you reach the very edge, the image frequency is the highest, and the edge is the most blurry. High-pass filtering kicks out low-frequency signal impacts, improving clarity at the edges.

The combination of the two can be regarded as a certain achievement in the processing of the airspace algorithm. 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 calculate the gray value of the image.

This technology is divided into two types: point operation and neighborhood enhancement operation. Firstly, Lu Chuan used the dot operation algorithm to correct, transform and correct the grayscale.

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

After that, Lu Chuan uses the neighborhood enhancement algorithm to smooth or sharpen the image. At present, many high-end mobile phones on the market actually have functions such as sharpening and grayscale value adjustment.

But compared with Lu Chuan's processing on the computer and using professional PS paid software, it is as big as the difference between singing downstairs and firing upstairs.

The two are not of an order of magnitude. For the processing of every fingerprint, Lu Chuan has to go through such a process.

On average, it takes almost an hour to process a fingerprint. However, even so, after Lu Chuan finished processing, he still couldn't use the exact matching function of the fingerprint system.

Because the number of annotations of feature points is insufficient. The judicial effect of fingerprint identification is related to the proficiency of feature point matching in the process of fingerprint identification and analysis, and it is an absolute relationship.

If there are less than 13 marking points of the same token, fingerprint identification and analysis have no legal effect. Of course, in this case, it does not mean that fingerprint identification analysis is useless.

Because as long as there are no clear points of similarities and differences, the identity of the suspect can actually be corroborated. As long as the identity of the other party is confirmed, even if there is no fingerprint evidence, the police handling the case can always dig up other evidence.

As long as people can find it, everything else will be easy. Open the fingerprint comparison system, the second commonly used comparison method in the system adopted by Lu Chuan.

Similarity comparison. Five fingerprints means that Lu Chuan has five chances. The first fingerprint was not well compared.

The system directly gives a failure comparison. This means that there are similarities and differences between this fingerprint and all fingerprints in the system, that is, the comparison failure is determined.

The second fingerprint still failed. In front of the computer, Lu Chuan was not discouraged, if the advanced fingerprint identification and analysis skills can't get this fingerprint, then it is estimated that there are few people in the country who can get this fingerprint.

The third fingerprint comparison ...... Failed again. Looking at the last two fingerprints that had been pre-processed at hand, Lu Chuan took a deep breath.

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

Because these five fingerprints were so mutilated, after Lu Chuan preprocessed, the results obtained were very different.

Therefore, if it is not successful, Lu Chuan has already made plans to preprocess the original fingerprint again.

While thinking about it, 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.

Drip, drip, drip. and exactly matched

The "ding" prompt sound is different, and this time the system gives a continuous dripping sound. Lu Chuan perked up and looked at the screen carefully.

The similarity match is successful. In the list, there are twenty-eight fingerprints lying there quietly, waiting for Lu Chuan to appreciate them one by one.

"Good!" Lu Chuan struck with both palms, and his mood was very high. Fingerprint identification and analysis requires both technology and sometimes luck.

Or the feel. After doing so many fingerprint identification and analysis, Lu Chuan knows very well that the feeling of fingerprint pretreatment for the first time is very important.

If the fingerprint of the first processing is not matched, the further it goes, the greater the distortion of the processing, and the less likely it is that the comparison will be successful.

Of course, this does not mean that the comparison will not be successful. Kung fu is not afraid of people with a heart, no matter how thick the iron pestle is, if there is more friction, it must be thinner.

No matter how bad it is, you can rub and vomit. Twenty-eight similar fingerprints were sorted by the number of similar feature points.

Of course, this does not mean that the first place in the ranking must be the target fingerprint, and the last in the ranking may also be possible.

The point is that the original fingerprint is too badly mutilated, only one-third the size, and it is still blurred into an extremely distorted state.

Taking a deep breath, Lu Chuan started to manually check the fingerprints that were ranked first. This time, Lu Chuan did not just check with the pre-processed 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 trace inspection criminal police also have to sort out and compare them one by one.

Until obvious similarities and differences are found, the judgment comparison fails. Or no similarities or differences have been found, and the sameness is determined.

Twenty-eight fingerprints, the first fingerprint has a high degree of similarity, but it is also easy to find similarities and differences. In less than five minutes, Lu Chuan found two obvious similarities and differences.

After marking, this fingerprint is considered goodbye. Then there is the second fingerprint, Lu Chuan combed them one by one along the middle lines, and then compared them with the original fingerprint.

This time the time was shorter, and the battle ended in three minutes. Third Fingerprint ...... Two minutes. Then the fourth, the fifth...... Just like in the beauty pageant in the clubhouse, more than 20 destined female bodhisattvas stand in a row, but who can purify the lonely souls of the guests cannot listen to the manager's introduction.

Listening to his introduction, all of them are boundless in mana. At this time, it is necessary to screen all distracting thoughts, start from the beginning, pick one by one, and look at them one by one.

Is the hair you like, the advantages are prominent enough, the eyes are not what you like, and the skirt slit is in place...... Click!

Lu Chuan, who had already compared the nineteenth fingerprint, seemed to have a lightning bolt in his mind. The eyes lit up, and the mind cleared.

That means that fate has arrived, and it's you! The nineteenth fingerprint, Lu Chuan put it in place from the beginning, and the entire one-third of the fingerprints were all compared, and no obvious similarities and differences were found.

Of course, this does not mean that the owner of this fingerprint must be the murderer. After all, there is a possibility that one-third of a fingerprint is the same as that of other people.

Although this probability is very small, there is a case, which cannot be used as judicial evidence to accuse 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, and then look for other evidence, it will be easy to do.