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+// ==========================================================
+// Bitmap conversion routines
+// Thresholding and halftoning functions
+// Design and implementation by
+// - Hervé Drolon (drolon@infonie.fr)
+// - Dennis Lim (dlkj@users.sourceforge.net)
+// - Thomas Chmielewski (Chmielewski.Thomas@oce.de)
+//
+// Main reference : Ulichney, R., Digital Halftoning, The MIT Press, Cambridge, MA, 1987
+//
+// This file is part of FreeImage 3
+//
+// COVERED CODE IS PROVIDED UNDER THIS LICENSE ON AN "AS IS" BASIS, WITHOUT WARRANTY
+// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES
+// THAT THE COVERED CODE IS FREE OF DEFECTS, MERCHANTABLE, FIT FOR A PARTICULAR PURPOSE
+// OR NON-INFRINGING. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE COVERED
+// CODE IS WITH YOU. SHOULD ANY COVERED CODE PROVE DEFECTIVE IN ANY RESPECT, YOU (NOT
+// THE INITIAL DEVELOPER OR ANY OTHER CONTRIBUTOR) ASSUME THE COST OF ANY NECESSARY
+// SERVICING, REPAIR OR CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL
+// PART OF THIS LICENSE. NO USE OF ANY COVERED CODE IS AUTHORIZED HEREUNDER EXCEPT UNDER
+// THIS DISCLAIMER.
+//
+// Use at your own risk!
+// ==========================================================
+
+#include "FreeImage.h"
+#include "Utilities.h"
+
+static const int WHITE = 255;
+static const int BLACK = 0;
+
+// Floyd & Steinberg error diffusion dithering
+// This algorithm use the following filter
+// * 7
+// 3 5 1 (1/16)
+static FIBITMAP* FloydSteinberg(FIBITMAP *dib) {
+
+#define RAND(RN) (((seed = 1103515245 * seed + 12345) >> 12) % (RN))
+#define INITERR(X, Y) (((int) X) - (((int) Y) ? WHITE : BLACK) + ((WHITE/2)-((int)X)) / 2)
+
+ int seed = 0;
+ int x, y, p, pixel, threshold, error;
+ int width, height, pitch;
+ BYTE *bits, *new_bits;
+ FIBITMAP *new_dib = NULL;
+
+ // allocate a 8-bit DIB
+ width = FreeImage_GetWidth(dib);
+ height = FreeImage_GetHeight(dib);
+ pitch = FreeImage_GetPitch(dib);
+ new_dib = FreeImage_Allocate(width, height, 8);
+ if(NULL == new_dib) return NULL;
+
+ // allocate space for error arrays
+ int *lerr = (int*)malloc (width * sizeof(int));
+ int *cerr = (int*)malloc (width * sizeof(int));
+ memset(lerr, 0, width * sizeof(int));
+ memset(cerr, 0, width * sizeof(int));
+
+ // left border
+ error = 0;
+ for(y = 0; y < height; y++) {
+ bits = FreeImage_GetScanLine(dib, y);
+ new_bits = FreeImage_GetScanLine(new_dib, y);
+
+ threshold = (WHITE / 2 + RAND(129) - 64);
+ pixel = bits[0] + error;
+ p = (pixel > threshold) ? WHITE : BLACK;
+ error = pixel - p;
+ new_bits[0] = (BYTE)p;
+ }
+ // right border
+ error = 0;
+ for(y = 0; y < height; y++) {
+ bits = FreeImage_GetScanLine(dib, y);
+ new_bits = FreeImage_GetScanLine(new_dib, y);
+
+ threshold = (WHITE / 2 + RAND(129) - 64);
+ pixel = bits[width-1] + error;
+ p = (pixel > threshold) ? WHITE : BLACK;
+ error = pixel - p;
+ new_bits[width-1] = (BYTE)p;
+ }
+ // top border
+ bits = FreeImage_GetBits(dib);
+ new_bits = FreeImage_GetBits(new_dib);
+ error = 0;
+ for(x = 0; x < width; x++) {
+ threshold = (WHITE / 2 + RAND(129) - 64);
+ pixel = bits[x] + error;
+ p = (pixel > threshold) ? WHITE : BLACK;
+ error = pixel - p;
+ new_bits[x] = (BYTE)p;
+ lerr[x] = INITERR(bits[x], p);
+ }
+
+ // interior bits
+ for(y = 1; y < height; y++) {
+ // scan left to right
+ bits = FreeImage_GetScanLine(dib, y);
+ new_bits = FreeImage_GetScanLine(new_dib, y);
+
+ cerr[0] = INITERR(bits[0], new_bits[0]);
+ for(x = 1; x < width - 1; x++) {
+ error = (lerr[x-1] + 5 * lerr[x] + 3 * lerr[x+1] + 7 * cerr[x-1]) / 16;
+ pixel = bits[x] + error;
+ if(pixel > (WHITE / 2)) {
+ new_bits[x] = WHITE;
+ cerr[x] = pixel - WHITE;
+ } else {
+ new_bits[x] = BLACK;
+ cerr[x] = pixel - BLACK;
+ }
+ }
+ // set errors for ends of the row
+ cerr[0] = INITERR (bits[0], new_bits[0]);
+ cerr[width - 1] = INITERR (bits[width - 1], new_bits[width - 1]);
+
+ // swap error buffers
+ int *terr = lerr; lerr = cerr; cerr = terr;
+ }
+
+ free(lerr);
+ free(cerr);
+
+ return new_dib;
+}
+
+// ==========================================================
+// Bayer ordered dispersed dot dithering
+//
+
+// Function taken from "Ordered Dithering, Stephen Hawley, Graphics Gems, Academic Press, 1990"
+// This function is used to generate a Bayer dithering matrice whose dimension are 2^size by 2^size
+//
+static int dithervalue(int x, int y, int size) {
+ int d = 0;
+ /*
+ * calculate the dither value at a particular
+ * (x, y) over the size of the matrix.
+ */
+ while (size-->0) {
+ /* Think of d as the density. At every iteration,
+ * d is shifted left one and a new bit is put in the
+ * low bit based on x and y. If x is odd and y is even,
+ * or x is even and y is odd, a bit is put in. This
+ * generates the checkerboard seen in dithering.
+ * This quantity is shifted left again and the low bit of
+ * y is added in.
+ * This whole thing interleaves a checkerboard bit pattern
+ * and y's bits, which is the value you want.
+ */
+ d = (d <<1 | (x&1 ^ y&1))<<1 | y&1;
+ x >>= 1;
+ y >>= 1;
+ }
+ return d;
+}
+
+// Ordered dithering with a Bayer matrix of size 2^order by 2^order
+//
+static FIBITMAP* OrderedDispersedDot(FIBITMAP *dib, int order) {
+ int x, y;
+ 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;
+
+ // build the dithering matrix
+ int l = (1 << order); // square of dither matrix order; the dimensions of the matrix
+ BYTE *matrix = (BYTE*)malloc(l*l * sizeof(BYTE));
+ for(int i = 0; i < l*l; i++) {
+ // according to "Purdue University: Digital Image Processing Laboratory: Image Halftoning, April 30th, 2006
+ matrix[i] = (BYTE)( 255 * (((double)dithervalue(i / l, i % l, order) + 0.5) / (l*l)) );
+ }
+
+ // 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++) {
+ if(bits[x] > matrix[(x % l) + l * (y % l)]) {
+ new_bits[x] = WHITE;
+ } else {
+ new_bits[x] = BLACK;
+ }
+ }
+ }
+
+ free(matrix);
+
+ return new_dib;
+}
+
+// ==========================================================
+// Ordered clustered dot dithering
+//
+
+// 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(NULL == 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
+ RGBQUAD *pal = FreeImage_GetPalette(new_dib);
+ pal[0].rgbRed = pal[0].rgbGreen = pal[0].rgbBlue = 0;
+ pal[1].rgbRed = pal[1].rgbGreen = pal[1].rgbBlue = 255;
+ }
+ return new_dib;
+ }
+
+ // Convert the input dib to a 8-bit greyscale dib
+ //
+ switch(bpp) {
+ case 8:
+ if(FreeImage_GetColorType(dib) == FIC_MINISBLACK) {
+ input = dib;
+ } else {
+ input = FreeImage_ConvertToGreyscale(dib);
+ }
+ break;
+ case 4:
+ case 16:
+ case 24:
+ case 32:
+ input = FreeImage_ConvertToGreyscale(dib);
+ break;
+ }
+ if(NULL == input) return NULL;
+
+ // Apply the dithering algorithm
+ switch(algorithm) {
+ case FID_FS:
+ dib8 = FloydSteinberg(input);
+ break;
+ case FID_BAYER4x4:
+ dib8 = OrderedDispersedDot(input, 2);
+ break;
+ case FID_BAYER8x8:
+ dib8 = OrderedDispersedDot(input, 3);
+ break;
+ case FID_BAYER16x16:
+ dib8 = OrderedDispersedDot(input, 4);
+ break;
+ case FID_CLUSTER6x6:
+ dib8 = OrderedClusteredDot(input, 3);
+ break;
+ case FID_CLUSTER8x8:
+ dib8 = OrderedClusteredDot(input, 4);
+ break;
+ case FID_CLUSTER16x16:
+ dib8 = OrderedClusteredDot(input, 8);
+ break;
+ }
+ if(input != dib) {
+ FreeImage_Unload(input);
+ }
+
+ // Build a greyscale palette (needed by threshold)
+ RGBQUAD *grey_pal = FreeImage_GetPalette(dib8);
+ for(int i = 0; i < 256; i++) {
+ grey_pal[i].rgbRed = (BYTE)i;
+ grey_pal[i].rgbGreen = (BYTE)i;
+ grey_pal[i].rgbBlue = (BYTE)i;
+ }
+
+ // Convert to 1-bit
+ FIBITMAP *new_dib = FreeImage_Threshold(dib8, 128);
+ FreeImage_Unload(dib8);
+
+ // copy metadata from src to dst
+ FreeImage_CloneMetadata(new_dib, dib);
+
+ return new_dib;
+}
+
+// ==========================================================
+// Thresholding function
+//
+FIBITMAP * DLL_CALLCONV
+FreeImage_Threshold(FIBITMAP *dib, BYTE T) {
+ FIBITMAP *dib8 = NULL;
+
+ if(NULL == 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
+ RGBQUAD *pal = FreeImage_GetPalette(new_dib);
+ pal[0].rgbRed = pal[0].rgbGreen = pal[0].rgbBlue = 0;
+ pal[1].rgbRed = pal[1].rgbGreen = pal[1].rgbBlue = 255;
+ }
+ return new_dib;
+ }
+
+ // Convert the input dib to a 8-bit greyscale dib
+ //
+ switch(bpp) {
+ case 8:
+ if(FreeImage_GetColorType(dib) == FIC_MINISBLACK) {
+ dib8 = dib;
+ } else {
+ dib8 = FreeImage_ConvertToGreyscale(dib);
+ }
+ break;
+ case 4:
+ case 16:
+ case 24:
+ case 32:
+ dib8 = FreeImage_ConvertToGreyscale(dib);
+ break;
+ }
+ if(NULL == dib8) return NULL;
+
+ // Allocate a new 1-bit DIB
+ int width = FreeImage_GetWidth(dib);
+ int height = FreeImage_GetHeight(dib);
+ FIBITMAP *new_dib = FreeImage_Allocate(width, height, 1);
+ if(NULL == new_dib) return NULL;
+ // Build a monochrome palette
+ RGBQUAD *pal = FreeImage_GetPalette(new_dib);
+ pal[0].rgbRed = pal[0].rgbGreen = pal[0].rgbBlue = 0;
+ pal[1].rgbRed = pal[1].rgbGreen = pal[1].rgbBlue = 255;
+
+ // Perform the thresholding
+ //
+ for(int y = 0; y < height; y++) {
+ BYTE *bits8 = FreeImage_GetScanLine(dib8, y);
+ BYTE *bits1 = FreeImage_GetScanLine(new_dib, y);
+ for(int x = 0; x < width; x++) {
+ if(bits8[x] < T) {
+ // Set bit(x, y) to 0
+ bits1[x >> 3] &= (0xFF7F >> (x & 0x7));
+ } else {
+ // Set bit(x, y) to 1
+ bits1[x >> 3] |= (0x80 >> (x & 0x7));
+ }
+ }
+ }
+ if(dib8 != dib) {
+ FreeImage_Unload(dib8);
+ }
+
+ // copy metadata from src to dst
+ FreeImage_CloneMetadata(new_dib, dib);
+
+ return new_dib;
+}
+
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