# erich666/GraphicsGems

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 /* * C code from the article * "Efficient Binary Image Thinning using Neighborhood Maps" * by Joseph M. Cychosz, 3ksnn64@ecn.purdue.edu * in "Graphics Gems IV", Academic Press, 1994 */ #include #include typedef unsigned char Pixel; /* Pixel data type */ typedef struct { /* Image control structure */ short Hres; /* Horizontal resolution (x) */ short Vres; /* Vertical resolution (y) */ int Size; /* Image size (bytes) */ Pixel *i; /* Image array */ Pixel *p[1]; /* Scanline pointer array */ /* Pixel (x,y) is given by */ /* image->p[y][x] */ } Image; /* ---- ThinImage - Thin binary image. -------------------------------- */ /* */ /* Description: */ /* Thins the supplied binary image using Rosenfeld's parallel */ /* thinning algorithm. */ /* */ /* On Entry: */ /* image = Image to thin. */ /* */ /* -------------------------------------------------------------------- */ /* Direction masks: */ /* N S W E */ static int masks[] = { 0200, 0002, 0040, 0010 }; /* True if pixel neighbor map indicates the pixel is 8-simple and */ /* not an end point and thus can be deleted. The neighborhood */ /* map is defined as an integer of bits abcdefghi with a non-zero */ /* bit representing a non-zero pixel. The bit assignment for the */ /* neighborhood is: */ /* */ /* a b c */ /* d e f */ /* g h i */ static unsigned char delete[512] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}; void ThinImage (image) Image *image; /* Image control structure */ { int xsize, ysize; /* Image resolution */ int x, y; /* Pixel location */ int i; /* Pass index */ int pc = 0; /* Pass count */ int count = 1; /* Deleted pixel count */ int p, q; /* Neighborhood maps of adjacent*/ /* cells */ Pixel *qb; /* Neighborhood maps of previous*/ /* scanline */ int m; /* Deletion direction mask */ xsize = image->Hres; ysize = image->Vres; qb = (Pixel *) malloc (xsize*sizeof(Pixel)); qb[xsize-1] = 0; /* Used for lower-right pixel */ while ( count ) { /* Scan image while deletions */ pc++; count = 0; for ( i = 0 ; i < 4 ; i++ ) { m = masks[i]; /* Build initial previous scan buffer. */ p = image->p[0][0] != 0; for ( x = 0 ; x < xsize-1 ; x++ ) qb[x] = p = ((p<<1)&0006) | (image->p[0][x+1] != 0); /* Scan image for pixel deletion candidates. */ for ( y = 0 ; y < ysize-1 ; y++ ) { q = qb[0]; p = ((q<<3)&0110) | (image->p[y+1][0] != 0); for ( x = 0 ; x < xsize-1 ; x++ ) { q = qb[x]; p = ((p<<1)&0666) | ((q<<3)&0110) | (image->p[y+1][x+1] != 0); qb[x] = p; if ( ((p&m) == 0) && delete[p] ) { count++; image->p[y][x] = 0; } } /* Process right edge pixel. */ p = (p<<1)&0666; if ( (p&m) == 0 && delete[p] ) { count++; image->p[y][xsize-1] = 0; } } /* Process bottom scan line. */ for ( x = 0 ; x < xsize ; x++ ) { q = qb[x]; p = ((p<<1)&0666) | ((q<<3)&0110); if ( (p&m) == 0 && delete[p] ) { count++; image->p[ysize-1][x] = 0; } } } printf ("ThinImage: pass %d, %d pixels deleted\n", pc, count); } free (qb); }