Encode and Decode a radar images
As described above, a radar image contains 401×401 data points, each point is an interger taking value from 0 to 2000.
By performing the Huffman encoder, we obtained the following codes (Figure 1).
By using these codes, the total number of bits of one specific image is 416,924 bits, which is much smaller than the codes using 11-bits length.
In actual work, we can convert an image data to bits by concatenate value by value, then write everything to a binary file. As computer groups every 8 bits to a byte, then the binary file consume 416,924/8 bits = 52KB.
To decode a binary file back to the image array, we load the binary file and trasform it to bit. As the Huffman code verifies the ‘prefix’ condition, by searching and maping, the original data can always be reconstructed without loosing any information.
If we write image array in the numpy format, then the storage can be up to 1.3MB/array. Now with Huffman compression, the storage can be reduced to 52KB.
If we use ‘ZIP’ application to compress the numpy file, the storage of the zip file is only 48KB, meaning that the ‘ZIP’ is outperform our Huffman encoding. That is because ZIP is using another encoding algorithm that allows to reach closer to the lower bound of compression.
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