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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(!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
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(!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
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;
}