invbytes.c

NIST Handwriting OCR Testbed

/*
# proc: inv_bytes - takes an array of bytes and inverts them using a
# proc:             lookup table. invert = reverse bits within a byte
*/

/* this from octal dump of /usr/local/image/lut/inv_bytes.lut	*/
/* itself from /usr/local/image/src/bin/inv_byte/makelut.c	*/

/* see the include file /usr/local/image/include/inv_byte.h	*/

unsigned char Inv_Byte[256] = {
  0,128, 64,192, 32,160, 96,224,
 16,144, 80,208, 48,176,112,240,
  8,136, 72,200, 40,168,104,232,
 24,152, 88,216, 56,184,120,248,
  4,132, 68,196, 36,164,100,228,
 20,148, 84,212, 52,180,116,244,
 12,140, 76,204, 44,172,108,236,
 28,156, 92,220, 60,188,124,252,
  2,130, 66,194, 34,162, 98,226,
 18,146, 82,210, 50,178,114,242,
 10,138, 74,202, 42,170,106,234,
 26,154, 90,218, 58,186,122,250,
  6,134, 70,198, 38,166,102,230,
 22,150, 86,214, 54,182,118,246,
 14,142, 78,206, 46,174,110,238,
 30,158, 94,222, 62,190,126,254,
  1,129, 65,193, 33,161, 97,225,
 17,145, 81,209, 49,177,113,241,
  9,137, 73,201, 41,169,105,233,
 25,153, 89,217, 57,185,121,249,
  5,133, 69,197, 37,165,101,229,
 21,149, 85,213, 53,181,117,245,
 13,141, 77,205, 45,173,109,237,
 29,157, 93,221, 61,189,125,253,
  3,131, 67,195, 35,163, 99,227,
 19,147, 83,211, 51,179,115,243,
 11,139, 75,203, 43,171,107,235,
 27,155, 91,219, 59,187,123,251,
  7,135, 71,199, 39,167,103,231,
 23,151, 87,215, 55,183,119,247,
 15,143, 79,207, 47,175,111,239,
 31,159, 95,223, 63,191,127,255};

inv_bytes(data, nbytes)
unsigned char *data;
int nbytes;
{
   for ( ; nbytes ; nbytes--, data++ )
      *data = Inv_Byte[*data];
}