It is like multiplying a number with 2. You tell me your number and i will divide it with 2 to get the result. This is not recovery. Recovery should be getting a number without knowing the exact algorithm that the number is made of.
This method is useless if you don't know the precise algorithm used to blur the text. Since you are using the same filter to blur the text this is not recovering cencored text. This is more likely "Javascript to compare and rank based on similarity".