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Text File  |  1992-03-30  |  7KB  |  214 lines
  1. /*******************************************************************************
  2.  
  3.             Optimized Bitmap Scaling Routines
  4.                 by Dale Schumacher
  5.  
  6. *******************************************************************************/
  7.  
  8. typedef struct {
  9.     int        xsize;        /* length of each scanline in pixels */
  10.     int        ysize;        /* number of scanlines in the image */
  11.     int        yspan;        /* byte offset between scanlines */
  12.     unsigned char *    data;        /* pointer to bitmap data */
  13. } Bitmap;
  14.  
  15. static unsigned char
  16. redux_6_of_8[256] = {
  17. 0x00,0x01,0x02,0x03,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x04,0x05,0x06,0x07,
  18. 0x08,0x09,0x0a,0x0b,0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f,0x0c,0x0d,0x0e,0x0f,
  19. 0x10,0x11,0x12,0x13,0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x14,0x15,0x16,0x17,
  20. 0x18,0x19,0x1a,0x1b,0x18,0x19,0x1a,0x1b,0x1c,0x1d,0x1e,0x1f,0x1c,0x1d,0x1e,0x1f,
  21. 0x00,0x01,0x02,0x03,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x04,0x05,0x06,0x07,
  22. 0x08,0x09,0x0a,0x0b,0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f,0x0c,0x0d,0x0e,0x0f,
  23. 0x10,0x11,0x12,0x13,0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x14,0x15,0x16,0x17,
  24. 0x18,0x19,0x1a,0x1b,0x18,0x19,0x1a,0x1b,0x1c,0x1d,0x1e,0x1f,0x1c,0x1d,0x1e,0x1f,
  25. 0x20,0x21,0x22,0x23,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x24,0x25,0x26,0x27,
  26. 0x28,0x29,0x2a,0x2b,0x28,0x29,0x2a,0x2b,0x2c,0x2d,0x2e,0x2f,0x2c,0x2d,0x2e,0x2f,
  27. 0x30,0x31,0x32,0x33,0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x34,0x35,0x36,0x37,
  28. 0x38,0x39,0x3a,0x3b,0x38,0x39,0x3a,0x3b,0x3c,0x3d,0x3e,0x3f,0x3c,0x3d,0x3e,0x3f,
  29. 0x20,0x21,0x22,0x23,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x24,0x25,0x26,0x27,
  30. 0x28,0x29,0x2a,0x2b,0x28,0x29,0x2a,0x2b,0x2c,0x2d,0x2e,0x2f,0x2c,0x2d,0x2e,0x2f,
  31. 0x30,0x31,0x32,0x33,0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x34,0x35,0x36,0x37,
  32. 0x38,0x39,0x3a,0x3b,0x38,0x39,0x3a,0x3b,0x3c,0x3d,0x3e,0x3f,0x3c,0x3d,0x3e,0x3f
  33. };
  34.  
  35. void
  36. scale_bitmap_6_of_8(dst, src)
  37. Bitmap *dst, *src;
  38. {
  39.     register int bitbuf, bits;
  40.     register int x, y, i, j, xbytes;
  41.     unsigned char *p, *pp, *q, *qq;
  42.  
  43.     xbytes = src->xsize / 8;
  44.     qq = src->data;
  45.     pp = dst->data;
  46.     for(y = 0; y < src->ysize; ++y) {
  47.         bits = 0;
  48.         p = pp;
  49.         q = qq;
  50.         qq += src->yspan;
  51.         j = y & 0x03;
  52.         if(j == 2) {
  53.             continue;    /* skip scanline */
  54.         }
  55.         pp += dst->yspan;
  56.         for(x = 0; x < xbytes; ++x) {
  57.             bitbuf <<= 6;
  58.             bitbuf |= redux_6_of_8[*q++];
  59.             bits += 6;
  60.             if(bits >= 8) {
  61.                 *p++ = bitbuf >> (bits - 8);
  62.                 bits -= 8;
  63.             }
  64.         }
  65.     }
  66. }
  67.  
  68. static unsigned char
  69. redux_3_of_8[256] = {
  70. 0x00,0x00,0x00,0x01,0x00,0x01,0x01,0x01,0x00,0x01,0x00,0x01,0x02,0x03,0x03,0x03,
  71. 0x00,0x00,0x00,0x01,0x02,0x03,0x03,0x03,0x02,0x03,0x02,0x03,0x02,0x03,0x03,0x03,
  72. 0x00,0x00,0x00,0x01,0x00,0x01,0x01,0x01,0x02,0x03,0x02,0x03,0x02,0x03,0x03,0x03,
  73. 0x02,0x02,0x02,0x03,0x02,0x03,0x03,0x03,0x02,0x03,0x02,0x03,0x02,0x03,0x03,0x03,
  74. 0x00,0x00,0x00,0x01,0x00,0x01,0x01,0x01,0x00,0x01,0x00,0x01,0x02,0x03,0x03,0x03,
  75. 0x04,0x04,0x04,0x05,0x06,0x07,0x07,0x07,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  76. 0x04,0x04,0x04,0x05,0x04,0x05,0x05,0x05,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  77. 0x06,0x06,0x06,0x07,0x06,0x07,0x07,0x07,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  78. 0x00,0x00,0x00,0x01,0x00,0x01,0x01,0x01,0x00,0x01,0x00,0x01,0x02,0x03,0x03,0x03,
  79. 0x00,0x00,0x00,0x01,0x02,0x03,0x03,0x03,0x02,0x03,0x02,0x03,0x02,0x03,0x03,0x03,
  80. 0x04,0x04,0x04,0x05,0x04,0x05,0x05,0x05,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  81. 0x06,0x06,0x06,0x07,0x06,0x07,0x07,0x07,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  82. 0x04,0x04,0x04,0x05,0x04,0x05,0x05,0x05,0x04,0x05,0x04,0x05,0x06,0x07,0x07,0x07,
  83. 0x04,0x04,0x04,0x05,0x06,0x07,0x07,0x07,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  84. 0x04,0x04,0x04,0x05,0x04,0x05,0x05,0x05,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07,
  85. 0x06,0x06,0x06,0x07,0x06,0x07,0x07,0x07,0x06,0x07,0x06,0x07,0x06,0x07,0x07,0x07
  86. };
  87.  
  88. void
  89. scale_bitmap_3_of_8(dst, src)
  90. Bitmap *dst, *src;
  91. {
  92.     register int bitbuf, bits;
  93.     register int x, y, i, j, xbytes;
  94.     unsigned char *p, *pp, *q, *qq;
  95.  
  96.     xbytes = src->xsize / 8;
  97.     qq = src->data;
  98.     pp = dst->data;
  99.     for(y = 0; y < src->ysize; ++y) {
  100.         bits = 0;
  101.         p = pp;
  102.         q = qq;
  103.         qq += src->yspan;
  104.         j = y & 7;
  105.         if(!((j == 1) || (j == 4) || (j == 7))) {
  106.             continue;    /* skip scanline */
  107.         }
  108.         pp += dst->yspan;
  109.         for(x = 0; x < xbytes; ++x) {
  110.             bitbuf <<= 3;
  111.             bitbuf |= redux_3_of_8[*q++];
  112.             bits += 3;
  113.             if(bits >= 8) {
  114.                 *p++ = bitbuf >> (bits - 8);
  115.                 bits -= 8;
  116.             }
  117.         }
  118.     }
  119. }
  120.  
  121. static unsigned short redux_7_of_16[0x10000];
  122.  
  123. void
  124. scale_bitmap_7_of_16(dst, src)
  125. Bitmap *dst, *src;
  126. {
  127.     static init_flag = 0;
  128.     register long bitbuf;
  129.     register int bits;
  130.     register int x, y, i, j, xwords;
  131.     unsigned char *p, *pp, *q, *qq;
  132.     unsigned short *dp, *dq;
  133.  
  134.     if(init_flag == 0) {    /* compute table at run time, but only once! */
  135. #define    BIT(b)    ((i >> (b)) & 1)    /* extract bit 'b' from int 'i' */
  136.         for(i = 0; i < 0x10000; ++i) {
  137.             redux_7_of_16[i] = (BIT(14) << 6)
  138.                      | (BIT(12) << 5)
  139.                      | (BIT(10) << 4)
  140.                      | ((BIT(8) | BIT(7)) << 3)
  141.                      | (BIT(5) << 2)
  142.                      | (BIT(3) << 1)
  143.                      | (BIT(1) | BIT(0));
  144.         }
  145.         init_flag = 1;
  146. #undef BIT
  147.     }
  148.     xwords = src->xsize / 16;
  149.     qq = src->data;
  150.     pp = dst->data;
  151.     for(y = 0; y < src->ysize; ++y) {
  152.         bits = 0;
  153.         dp = (unsigned short *)pp;
  154.         dq = (unsigned short *)qq;
  155.         qq += src->yspan;
  156.         j = y & 0xF;
  157.         if(!(j==1||j==3||j==5||j==8||j==10||j==12||j==14)) {
  158.             continue;    /* skip scanline */
  159.         }
  160.         pp += dst->yspan;
  161.         for(x = 0; x < xwords; ++x) {
  162.             bitbuf <<= 7;
  163.             bitbuf |= redux_7_of_16[*dq++];
  164.             bits += 7;
  165.             if(bits >= 16) {
  166.                 *dp++ = bitbuf >> (bits - 16);
  167.                 bits -= 16;
  168.             }
  169.         }
  170.     }
  171. }
  172.  
  173. static unsigned char
  174. bit_reverse_byte[256] = {
  175. 0x00,0x80,0x40,0xc0,0x20,0xa0,0x60,0xe0,0x10,0x90,0x50,0xd0,0x30,0xb0,0x70,0xf0,
  176. 0x08,0x88,0x48,0xc8,0x28,0xa8,0x68,0xe8,0x18,0x98,0x58,0xd8,0x38,0xb8,0x78,0xf8,
  177. 0x04,0x84,0x44,0xc4,0x24,0xa4,0x64,0xe4,0x14,0x94,0x54,0xd4,0x34,0xb4,0x74,0xf4,
  178. 0x0c,0x8c,0x4c,0xcc,0x2c,0xac,0x6c,0xec,0x1c,0x9c,0x5c,0xdc,0x3c,0xbc,0x7c,0xfc,
  179. 0x02,0x82,0x42,0xc2,0x22,0xa2,0x62,0xe2,0x12,0x92,0x52,0xd2,0x32,0xb2,0x72,0xf2,
  180. 0x0a,0x8a,0x4a,0xca,0x2a,0xaa,0x6a,0xea,0x1a,0x9a,0x5a,0xda,0x3a,0xba,0x7a,0xfa,
  181. 0x06,0x86,0x46,0xc6,0x26,0xa6,0x66,0xe6,0x16,0x96,0x56,0xd6,0x36,0xb6,0x76,0xf6,
  182. 0x0e,0x8e,0x4e,0xce,0x2e,0xae,0x6e,0xee,0x1e,0x9e,0x5e,0xde,0x3e,0xbe,0x7e,0xfe,
  183. 0x01,0x81,0x41,0xc1,0x21,0xa1,0x61,0xe1,0x11,0x91,0x51,0xd1,0x31,0xb1,0x71,0xf1,
  184. 0x09,0x89,0x49,0xc9,0x29,0xa9,0x69,0xe9,0x19,0x99,0x59,0xd9,0x39,0xb9,0x79,0xf9,
  185. 0x05,0x85,0x45,0xc5,0x25,0xa5,0x65,0xe5,0x15,0x95,0x55,0xd5,0x35,0xb5,0x75,0xf5,
  186. 0x0d,0x8d,0x4d,0xcd,0x2d,0xad,0x6d,0xed,0x1d,0x9d,0x5d,0xdd,0x3d,0xbd,0x7d,0xfd,
  187. 0x03,0x83,0x43,0xc3,0x23,0xa3,0x63,0xe3,0x13,0x93,0x53,0xd3,0x33,0xb3,0x73,0xf3,
  188. 0x0b,0x8b,0x4b,0xcb,0x2b,0xab,0x6b,0xeb,0x1b,0x9b,0x5b,0xdb,0x3b,0xbb,0x7b,0xfb,
  189. 0x07,0x87,0x47,0xc7,0x27,0xa7,0x67,0xe7,0x17,0x97,0x57,0xd7,0x37,0xb7,0x77,0xf7,
  190. 0x0f,0x8f,0x4f,0xcf,0x2f,0xaf,0x6f,0xef,0x1f,0x9f,0x5f,0xdf,0x3f,0xbf,0x7f,0xff
  191. };
  192.  
  193. void
  194. rotate_bitmap_180(dst, src)
  195. Bitmap *dst, *src;
  196. {
  197.     register int x, y, i, j, xbytes;
  198.     unsigned char *p, *pp, *q, *qq;
  199.  
  200.     xbytes = src->xsize / 8;
  201.     qq = dst->data;
  202.     pp = src->data;
  203.     pp += (src->yspan * src->ysize);
  204.     for(y = 0; y < src->ysize; ++y) {
  205.         q = qq;
  206.         qq += dst->yspan;
  207.         pp -= src->yspan;
  208.         p = pp + xbytes;
  209.         for(x = 0; x < xbytes; ++x) {
  210.             *q++ = bit_reverse_byte[*--p];
  211.         }
  212.     }
  213. }
  214.