Cannot apply bit mask
binary, bit, c#, digital
Solution
`face` and `eyesOnly` have no common 1-bits. `maskBits` leaves everything except for the eyes. Either swap `0` and `1`, or use the `~` operator to flip `maskBits`. And give it a better name so that it is clear what it is a mask for: `bitmaskForNotEyes`.
Problem
I am making a horse programme. I have the horse face and wish to apply a bit mask. Only the horses eyes should be visible when it is wearing the bit mask. First I must convert the horses face to digital. For this I have a set of bits which include 0, 0, 0, and 1 for the face of the horse. I am using C# and have broken the problem into parts: - Convert the horse's head to digital - Build a bit mask for it to wear - Put the bit mask on the horse - Convert the digital masked horse back into graphics At step 4 I expect only to see the horses eyes but I only see "0" which IS NOT EVEN A HORSE FACE. Here is all of my code, please don't question my ASCII art it is not relevant to the question, besides it is a prototype the real program will have superior graphics. ``` //the head of the horse string head = "# #" + "########" + "#O O#" + "# #" + "# #" + "#= =#" + " #====# " + " #### "; //digitize the horse into bits of binary string binaryHead = head.Replace('#', '0').Replace('=', '0').Replace(' ', '0').Replace('O', '1'); long face = Convert.ToInt64(binaryHead, 2); //make a bit mask with holes for the eyes string mask = "11111111" + "11111111" + "10111101" + "11111111" + "11111111" + "11111111" + "11111111" + "11111111"; //apply the bit mask using C# long maskBits = Convert.ToInt64(mask, 2); string eyesOnly = Convert.ToString(face & maskBits, 2); //eyesOnly is "0"....WHAT??? It should be more than that. WHERE IS THE HORSE?? //It should look like this: // "00000000" + // "00000000" + // "01000010" + // "00000000" + // "00000000" + // "00000000" + // "00000000" + // "00000000"; ``` I suspect something is wrong with the conversion, I have tried all kinds of things like converting to a byte array and formatting the string with spaces but with no luck. I am wondering if this problem might be NP-hard.