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src/Source/FreeImage/Halftoning.cpp  view on Meta::CPAN

// NB : The predefined dither matrices are the same as matrices used in 
// the Netpbm package (http://netpbm.sourceforge.net) and are defined in Ulichney's book.
// See also : The newsprint web site at http://www.cl.cam.ac.uk/~and1000/newsprint/
// for more technical info on this dithering technique
//
static FIBITMAP* OrderedClusteredDot(FIBITMAP *dib, int order) {
	// Order-3 clustered dithering matrix.
	int cluster3[] = {
	  9,11,10, 8, 6, 7,
	  12,17,16, 5, 0, 1,
	  13,14,15, 4, 3, 2,
	  8, 6, 7, 9,11,10,
	  5, 0, 1,12,17,16,
	  4, 3, 2,13,14,15
	};

	// Order-4 clustered dithering matrix. 
	int cluster4[] = {
	  18,20,19,16,13,11,12,15,
	  27,28,29,22, 4, 3, 2, 9,
	  26,31,30,21, 5, 0, 1,10,
	  23,25,24,17, 8, 6, 7,14,
	  13,11,12,15,18,20,19,16,
	  4, 3, 2, 9,27,28,29,22,
	  5, 0, 1,10,26,31,30,21,
	  8, 6, 7,14,23,25,24,17
	};

	// Order-8 clustered dithering matrix. 
	int cluster8[] = {
	   64, 69, 77, 87, 86, 76, 68, 67, 63, 58, 50, 40, 41, 51, 59, 60,
	   70, 94,100,109,108, 99, 93, 75, 57, 33, 27, 18, 19, 28, 34, 52,
	   78,101,114,116,115,112, 98, 83, 49, 26, 13, 11, 12, 15, 29, 44,
	   88,110,123,124,125,118,107, 85, 39, 17,  4,  3,  2,  9, 20, 42,
	   89,111,122,127,126,117,106, 84, 38, 16,  5,  0,  1, 10, 21, 43,
	   79,102,119,121,120,113, 97, 82, 48, 25,  8,  6,  7, 14, 30, 45,
	   71, 95,103,104,105, 96, 92, 74, 56, 32, 24, 23, 22, 31, 35, 53,
	   65, 72, 80, 90, 91, 81, 73, 66, 62, 55, 47, 37, 36, 46, 54, 61,
	   63, 58, 50, 40, 41, 51, 59, 60, 64, 69, 77, 87, 86, 76, 68, 67,
	   57, 33, 27, 18, 19, 28, 34, 52, 70, 94,100,109,108, 99, 93, 75,
	   49, 26, 13, 11, 12, 15, 29, 44, 78,101,114,116,115,112, 98, 83,
	   39, 17,  4,  3,  2,  9, 20, 42, 88,110,123,124,125,118,107, 85,
	   38, 16,  5,  0,  1, 10, 21, 43, 89,111,122,127,126,117,106, 84,
	   48, 25,  8,  6,  7, 14, 30, 45, 79,102,119,121,120,113, 97, 82,
	   56, 32, 24, 23, 22, 31, 35, 53, 71, 95,103,104,105, 96, 92, 74,
	   62, 55, 47, 37, 36, 46, 54, 61, 65, 72, 80, 90, 91, 81, 73, 66
	};

	int x, y, pixel;
	int width, height;
	BYTE *bits, *new_bits;
	FIBITMAP *new_dib = NULL;

	// allocate a 8-bit DIB
	width = FreeImage_GetWidth(dib);
	height = FreeImage_GetHeight(dib);
	new_dib = FreeImage_Allocate(width, height, 8);
	if(NULL == new_dib) return NULL;

	// select the dithering matrix
	int *matrix = NULL;
	switch(order) {
		case 3:
			matrix = &cluster3[0];
			break;
		case 4:
			matrix = &cluster4[0];
			break;
		case 8:
			matrix = &cluster8[0];
			break;
		default:
			return NULL;
	}

	// scale the dithering matrix
	int l = 2 * order;
	int scale = 256 / (l * order);
	for(y = 0; y < l; y++) {
		for(x = 0; x < l; x++) {
			matrix[y*l + x] *= scale;
		}
	}

	// perform the dithering
	for(y = 0; y < height; y++) {
		// scan left to right
		bits = FreeImage_GetScanLine(dib, y);
		new_bits = FreeImage_GetScanLine(new_dib, y);
		for(x = 0; x < width; x++) {
			pixel = bits[x];
			if(pixel >= matrix[(y % l) + l * (x % l)]) {
				new_bits[x] = WHITE;
			} else {
				new_bits[x] = BLACK;
			}
		}
	}

	return new_dib;
}


// ==========================================================
// Halftoning function
//
FIBITMAP * DLL_CALLCONV
FreeImage_Dither(FIBITMAP *dib, FREE_IMAGE_DITHER algorithm) {
	FIBITMAP *input = NULL, *dib8 = NULL;

	if(!FreeImage_HasPixels(dib)) return NULL;

	const unsigned bpp = FreeImage_GetBPP(dib);

	if(bpp == 1) {
		// Just clone the dib and adjust the palette if needed
		FIBITMAP *new_dib = FreeImage_Clone(dib);
		if(NULL == new_dib) return NULL;
		if(FreeImage_GetColorType(new_dib) == FIC_PALETTE) {
			// Build a monochrome palette