Translates hexidecimal digits into ASCII art, with the brightness correlated to the magnitude of the digit. The input may be either ASCII hex (either upper or lowercase) digits or machine values. Try it on random data, or the compiled executable of the program (and vary your terminal width). An octal version is also available.

hexBright.c

/* hexBright.c - visualize hex data with brightness
 * Max Goldstein
 *
 * example usage:
 * $ head /dev/urandom | hexdump -e '16/1 "%02x " "\n"' | ./hexBright
 */

#include <stdio.h>

int main(){
    while(1){
        int c = getchar();
        if (c == EOF){
            break;
        }else if (c >= '0' && c <= '9'){
            c -= '0';
        }else if (c >= 'A' && c <= 'F'){
            c -= 'A';
        }else if (c >= 'a' && c <= 'f'){
            c -= 'a';
        }else{
            continue;
        }
        putchar(" .:;-~=+a*&$#%M@"[c]);
    }
    putchar('\n');
    return 0;
}