Explanation for LSB data hiding

Please can someone explain what does the numbers 248, 252, 128, 64 denote, in

red = bitand(redc,248);
blue = bitand(bluec,252);

bitand(text,128) == 128
bitand(text,64) == 64

bitor(red,4)
bitor(red,2)
bitor(red,1)

The below is a few lines from LSB...

red = bitand(redc,248);
green = bitand(greenc,248);
blue = bitand(bluec,252);
if bitand(text,128) == 128
    red = bitor(red,4);
end
if bitand(text,64) == 64
    red = bitor(red,2);
end
if bitand(text,32) == 32
    red = bitor(red,1);
end

Answer 1

[dbmn]

you might get an answer if you leave the decimal notation and go to binary. Here is a mini example

dec2bin(248) = 11111000
dec2bin(252) = 11111100

So bitand(redc, 248) gets you all but the last 3 digits of your redc.

dec2bin(bitand(bin2dec('10101011'), 248)) = 10101000

I assume that you store whatever Info you need in that 3 digits. Similarly bitand(redc, 7) will get you the last 3 bits with the desired info.

dec2bin(bitand(bin2dec('10101011'), 7)) = 00000011

You might play around with bitand and bitor for clarity.