Solve the problem that QQ flash photos cannot be saved

Preface

When I am bored, I see the flash and wonder if I can save it , I studied it out of curiosity , Have figured out the general principle , Let's learn from each other . The following article only discusses the technology and principle .

principle

8.8.x The version is roughly the same as the previous version , Store the flash file on the client , Automatically destroy after viewing for five seconds . According to the online tutorial , I have divided the flash technology into three versions .

Version of a

In the early days, documents would not be destroyed , You can find it directly in the cache folder of the picture , Then change the suffix of the flash file to jpg、png You can view it later , But according to my practice , Now there are no flashed pictures in the cache folder , Therefore, a small number of online tutorials are basically invalid .

Version 2

At present, most of the online tutorials are for version 2 . This time I won't find it in the cache folder , When clicking the flash, the flash file will be downloaded to the folder where the flash is stored . It is worth noting that , You can only click on the flash , Can't view , Because this version of will destroy the flash file , But you don't have to long press to check . Then go to find the corresponding flash file , It is the same as version 1 , Change the suffix to view . According to my realization , The picture obtained by directly changing the suffix is a blank picture with nothing .

Version 3

No tutorial of this version has been found on the Internet , In order to test , I downgraded the version to 8.3.x Version 2 cannot use the method of version 2 , The version is too low to log in , There may be a version that can log in and use the version 2 method , I'm too lazy to try .
Preservation principle
Get the flash file according to the method of version 2 , At this time, the file is a specially processed picture , It can be regarded as encryption , It will decrypt the file when long press to view , At this point, we just need to change the suffix of the flash file .（ If a boss can decompile and find the encrypted algorithm , When I'm farting ）

Technical discussion

No source code , I dare to guess that the current practice of flash photography should be like this . Download flash file , The user triggers the long press event to decrypt the file , Then the file is displayed to the user . Of course, this is only about file processing , I don't know how to prevent screen capture .
As for why the flash image is not a picture format file, it may have its own processing algorithm , Processing this format will be faster than regular pictures ？
And why it doesn't read the file directly, decrypt it, and then display it , Wouldn't it be better to protect the flash photos from being acquired by the users ？
The above is just personal conjecture and doubt , I hope the big guy passing by can answer .

Conclusion

I wanted to share my thoughts , But too much said and too little reviewed , If you are interested, you can discuss it in the comment area or in a private letter .
As for the path of flash folder, it is available on the Internet , To baidu .