First cut at halftone support. Mono only, 16x16 default halftone.

Add fz_bitmaps (1bpc versions of pixmaps, really).
Add fz_halftones (arrays of fz_pixmaps used as threshold arrays).
Add simple halftoning code.
Add pdfdraw usage of the above (ask for a .pbm and you get a halftoned image).

6 files changed, 341 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 02776d59..6127571f 100644
--- a/Makefile
+++ b/Makefile
@@ -93,8 +93,10 @@ FITZ_SRC := \
 	fitz/obj_dict.c \
 	fitz/obj_print.c \
 	fitz/obj_simple.c \
+	fitz/res_bitmap.c \
 	fitz/res_colorspace.c \
 	fitz/res_font.c \
+	fitz/res_halftone.c \
 	fitz/res_path.c \
 	fitz/res_pixmap.c \
 	fitz/res_shade.c \
diff --git a/apps/pdfdraw.c b/apps/pdfdraw.c
index baaac92c..69a7d3aa 100644
--- a/apps/pdfdraw.c
+++ b/apps/pdfdraw.c
@@ -186,6 +186,13 @@ static void drawpage(pdf_xref *xref, int pagenum)
 				fz_write_pam(pix, buf, savealpha);
 			else if (strstr(output, ".png"))
 				fz_write_png(pix, buf, savealpha);
+			else if (strstr(output, ".pbm")) {
+				fz_halftone *ht = fz_get_default_halftone(1);
+				fz_bitmap *bit = fz_halftone_pixmap(pix, ht);
+				fz_write_pbm(bit, buf);
+				fz_drop_bitmap(bit);
+				fz_drop_halftone(ht);
+			}
 		}
 
 		if (showmd5)
@@ -327,6 +334,8 @@ int main(int argc, char **argv)
 		colorspace = fz_device_gray;
 	if (output && strstr(output, ".ppm"))
 		colorspace = fz_device_rgb;
+	if (output && strstr(output, ".pbm"))
+		colorspace = fz_device_gray;
 
 	timing.count = 0;
 	timing.total = 0;
diff --git a/fitz/fitz.h b/fitz/fitz.h
index 6e53a271..749c8919 100644
--- a/fitz/fitz.h
+++ b/fitz/fitz.h
@@ -700,6 +700,49 @@ fz_error fz_write_png(fz_pixmap *pixmap, char *filename, int savealpha);
 fz_error fz_load_jpx_image(fz_pixmap **imgp, unsigned char *data, int size, fz_colorspace *dcs);
 
 /*
+ * Bitmaps have 1 component per bit. Only used for creating halftoned versions
+ * of contone buffers, and saving out. Samples are stored msb first, akin to
+ * pbms.
+ */
+
+typedef struct fz_bitmap_s fz_bitmap;
+
+struct fz_bitmap_s
+{
+	int refs;
+	int w, h, span, n;
+	unsigned char *samples;
+};
+
+fz_bitmap *fz_new_bitmap(int w, int h, int n);
+fz_bitmap *fz_keep_bitmap(fz_bitmap *bit);
+void fz_clear_bitmap(fz_bitmap *bit);
+void fz_drop_bitmap(fz_bitmap *bit);
+
+fz_error fz_write_pbm(fz_bitmap *bitmap, char *filename);
+
+/*
+ * A halftone is a set of threshold tiles, one per component. Each threshold
+ * tile is a pixmap, possibly of varying sizes and phases.
+ */
+
+typedef struct fz_halftone_s fz_halftone;
+
+struct fz_halftone_s
+{
+	int refs;
+	int n;
+	fz_pixmap *comp[1];
+};
+
+fz_halftone *fz_new_halftone(int num_comps);
+fz_halftone *fz_get_default_halftone(int num_comps);
+fz_halftone *fz_keep_halftone(fz_halftone *half);
+void fz_drop_halftone(fz_halftone *half);
+
+fz_bitmap *fz_halftone_pixmap(fz_pixmap *pix, fz_halftone *ht);
+
+/*
  * Colorspace resources.
  */
 
diff --git a/fitz/res_bitmap.c b/fitz/res_bitmap.c
new file mode 100644
index 00000000..57784076
--- /dev/null
+++ b/fitz/res_bitmap.c
@@ -0,0 +1,76 @@
+#include "fitz.h"
+
+fz_bitmap *
+fz_new_bitmap(int w, int h, int n)
+{
+	fz_bitmap *bit;
+
+	bit = fz_malloc(sizeof(fz_bitmap));
+	bit->refs = 1;
+	bit->w = w;
+	bit->h = h;
+	bit->n = n;
+	/* Span is 32 bit aligned. We may want to make this 64 bit if we
+	 * use SSE2 etc. */
+	bit->span = ((n*w+31)&~31)>>3;
+
+	bit->samples = fz_calloc(h, bit->span);
+
+	return bit;
+}
+
+fz_bitmap *
+fz_keep_bitmap(fz_bitmap *pix)
+{
+	pix->refs++;
+	return pix;
+}
+
+void
+fz_drop_bitmap(fz_bitmap *bit)
+{
+	if (bit && --bit->refs == 0)
+	{
+		fz_free(bit->samples);
+		fz_free(bit);
+	}
+}
+
+void
+fz_clear_bitmap(fz_bitmap *bit)
+{
+	memset(bit->samples, 0, bit->span * bit->h);
+}
+
+/*
+ * Write bitmap to PBM file
+ */
+
+fz_error
+fz_write_pbm(fz_bitmap *bitmap, char *filename)
+{
+	FILE *fp;
+	unsigned char *p;
+	int h, bytespan;
+
+	fp = fopen(filename, "wb");
+	if (!fp)
+		return fz_throw("cannot open file '%s': %s", filename, strerror(errno));
+
+	assert(bitmap->n == 1);
+
+	fprintf(fp, "P4\n%d %d\n", bitmap->w, bitmap->h);
+
+	p = bitmap->samples;
+
+	h = bitmap->h;
+	bytespan = (bitmap->w+7)>>3;
+	while (h--)
+	{
+		fwrite(p, 1, bytespan, fp);
+		p += bitmap->span;
+	}
+
+	fclose(fp);
+	return fz_okay;
+}
diff --git a/fitz/res_halftone.c b/fitz/res_halftone.c
new file mode 100644
index 00000000..180c9c0a
--- /dev/null
+++ b/fitz/res_halftone.c
@@ -0,0 +1,203 @@
+#include "fitz.h"
+
+fz_halftone *
+fz_new_halftone(int comps)
+{
+	fz_halftone *ht;
+	int i;
+
+	ht = fz_malloc(sizeof(fz_halftone) + (comps-1)*sizeof(fz_pixmap *));
+	ht->refs = 1;
+	ht->n = comps;
+	for (i=0; i < comps; i++)
+		ht->comp[i] = NULL;
+
+	return ht;
+}
+
+fz_halftone *
+fz_keep_halftone(fz_halftone *ht)
+{
+	ht->refs++;
+	return ht;
+}
+
+void
+fz_drop_halftone(fz_halftone *ht)
+{
+	int i;
+
+	if (!ht || --ht->refs != 0)
+		return;
+	for (i=0; i < ht->n; i++)
+	{
+		fz_drop_pixmap(ht->comp[i]);
+	}
+	fz_free(ht);
+}
+
+/* Default mono halftone, lifted from Ghostscript. */
+static unsigned char mono_ht[] =
+{
+	0x0E, 0x8E, 0x2E, 0xAE, 0x06, 0x86, 0x26, 0xA6, 0x0C, 0x8C, 0x2C, 0xAC, 0x04, 0x84, 0x24, 0xA4,
+	0xCE, 0x4E, 0xEE, 0x6E, 0xC6, 0x46, 0xE6, 0x66, 0xCC, 0x4C, 0xEC, 0x6C, 0xC4, 0x44, 0xE4, 0x64,
+	0x3E, 0xBE, 0x1E, 0x9E, 0x36, 0xB6, 0x16, 0x96, 0x3C, 0xBC, 0x1C, 0x9C, 0x34, 0xB4, 0x14, 0x94,
+	0xFE, 0x7E, 0xDE, 0x5E, 0xF6, 0x76, 0xD6, 0x56, 0xFC, 0x7C, 0xDC, 0x5C, 0xF4, 0x74, 0xD4, 0x54,
+	0x01, 0x81, 0x21, 0xA1, 0x09, 0x89, 0x29, 0xA9, 0x03, 0x83, 0x23, 0xA3, 0x0B, 0x8B, 0x2B, 0xAB,
+	0xC1, 0x41, 0xE1, 0x61, 0xC9, 0x49, 0xE9, 0x69, 0xC3, 0x43, 0xE3, 0x63, 0xCB, 0x4B, 0xEB, 0x6B,
+	0x31, 0xB1, 0x11, 0x91, 0x39, 0xB9, 0x19, 0x99, 0x33, 0xB3, 0x13, 0x93, 0x3B, 0xBB, 0x1B, 0x9B,
+	0xF1, 0x71, 0xD1, 0x51, 0xF9, 0x79, 0xD9, 0x59, 0xF3, 0x73, 0xD3, 0x53, 0xFB, 0x7B, 0xDB, 0x5B,
+	0x0D, 0x8D, 0x2D, 0xAD, 0x05, 0x85, 0x25, 0xA5, 0x0F, 0x8F, 0x2F, 0xAF, 0x07, 0x87, 0x27, 0xA7,
+	0xCD, 0x4D, 0xED, 0x6D, 0xC5, 0x45, 0xE5, 0x65, 0xCF, 0x4F, 0xEF, 0x6F, 0xC7, 0x47, 0xE7, 0x67,
+	0x3D, 0xBD, 0x1D, 0x9D, 0x35, 0xB5, 0x15, 0x95, 0x3F, 0xBF, 0x1F, 0x9F, 0x37, 0xB7, 0x17, 0x97,
+	0xFD, 0x7D, 0xDD, 0x5D, 0xF5, 0x75, 0xD5, 0x55, 0xFF, 0x7F, 0xDF, 0x5F, 0xF7, 0x77, 0xD7, 0x57,
+	0x02, 0x82, 0x22, 0xA2, 0x0A, 0x8A, 0x2A, 0xAA, 0x00, 0x80, 0x20, 0xA0, 0x08, 0x88, 0x28, 0xA8,
+	0xC2, 0x42, 0xE2, 0x62, 0xCA, 0x4A, 0xEA, 0x6A, 0xC0, 0x40, 0xE0, 0x60, 0xC8, 0x48, 0xE8, 0x68,
+	0x32, 0xB2, 0x12, 0x92, 0x3A, 0xBA, 0x1A, 0x9A, 0x30, 0xB0, 0x10, 0x90, 0x38, 0xB8, 0x18, 0x98,
+	0xF2, 0x72, 0xD2, 0x52, 0xFA, 0x7A, 0xDA, 0x5A, 0xF0, 0x70, 0xD0, 0x50, 0xF8, 0x78, 0xD8, 0x58
+};
+
+fz_halftone *fz_get_default_halftone(int num_comps)
+{
+	fz_halftone *ht = fz_new_halftone(num_comps);
+
+	if (ht == NULL)
+		return NULL;
+
+	/* Only support 1 component for now */
+	assert(num_comps == 1);
+
+	ht->comp[0] = fz_new_pixmap_with_data(NULL, 0, 0, 16, 16, mono_ht);
+	if (ht->comp[0] == NULL)
+	{
+		fz_drop_halftone(ht);
+		return NULL;
+	}
+	return ht;
+}
+
+/* Finally, code to actually perform halftoning. */
+static void make_ht_line(unsigned char *buf, fz_halftone *ht, int x, int y, int w)
+{
+	/* FIXME: There is a potential optimisation here; in the case where
+	 * the LCM of the halftone tile widths is smaller than w, we could
+	 * form just one 'LCM' run, then copy it repeatedly.
+	 */
+	int k, n;
+	n = ht->n;
+	for (k=0; k < n; k++)
+	{
+		fz_pixmap *tile = ht->comp[k];
+		unsigned char *b = buf++;
+		unsigned char *t;
+		unsigned char *tbase;
+		int px = x + tile->x;
+		int py = y + tile->y;
+		int tw = tile->w;
+		int th = tile->h;
+		int w2 = w;
+		int len;
+		px = px % tw;
+		if (px < 0)
+			px += tw;
+		py = py % th;
+		if (py < 0)
+			py += th;
+
+		assert(tile->n == 1);
+
+		/* Left hand section; from x to tile width */
+		tbase = tile->samples + py * tw;
+		t = tbase + px;
+		len = tw - px;
+		if (len > w2)
+			len = w2;
+		w2 -= len;
+		while (len--)
+		{
+			*b = *t++;
+			b += n;
+		}
+
+		/* Centre section - complete copies */
+		w2 -= tw;
+		while (w2 >= 0)
+		{
+			len = tw;
+			t = tbase;
+			while (len--)
+			{
+				*b = *t++;
+				b += n;
+			}
+			w2 -= tw;
+		}
+		w2 += tw;
+
+		/* Right hand section - stragglers */
+		t = tbase;
+		while (w2--)
+		{
+			*b = *t++;
+			b += n;
+		}
+	}
+}
+
+/* Inner mono thresholding code */
+static void do_threshold_1(unsigned char *ht_line, unsigned char *pixmap, unsigned char *out, int w)
+{
+	int bit = 0x80;
+	int h = 0;
+
+	do
+	{
+		if (*pixmap < *ht_line++)
+			h |= bit;
+		pixmap += 2; /* Skip the alpha */
+		bit >>= 1;
+		if (bit == 0)
+		{
+			*out++ = h;
+			h = 0;
+			bit = 0x80;
+		}
+
+	}
+	while (--w);
+	if (bit != 0x80)
+		*out++ = h;
+}
+
+fz_bitmap *fz_halftone_pixmap(fz_pixmap *pix, fz_halftone *ht)
+{
+	fz_bitmap *out;
+	unsigned char *ht_line, *o, *p;
+	int w, h, x, y, n, pspan, ospan;
+
+	if ((pix == NULL) || (ht == NULL))
+		return NULL;
+
+	assert(pix->n == 2); /* Mono + Alpha */
+
+	n = pix->n-1; /* Remove alpha */
+	ht_line = fz_malloc(sizeof(unsigned char)*pix->w*n);
+	out = fz_new_bitmap(pix->w, pix->h, n);
+	o = out->samples;
+	p = pix->samples;
+
+	h = pix->h;
+	x = pix->x;
+	y = pix->y;
+	w = pix->w;
+	ospan = out->span;
+	pspan = pix->w * pix->n;
+	while (h--)
+	{
+		make_ht_line(ht_line, ht, x, y++, w);
+		do_threshold_1(ht_line, p, o, w);
+		o += ospan;
+		p += pspan;
+	}
+	return out;
+}
diff --git a/win32/libmupdf.vcproj b/win32/libmupdf.vcproj
index 0017a340..d58dc6e4 100644
--- a/win32/libmupdf.vcproj
+++ b/win32/libmupdf.vcproj
@@ -387,6 +387,10 @@
 				>
 			</File>
 			<File
+				RelativePath="..\fitz\res_bitmap.c"
+				>
+			</File>
+			<File
 				RelativePath="..\fitz\res_colorspace.c"
 				>
 			</File>
@@ -395,6 +399,10 @@
 				>
 			</File>
 			<File
+				RelativePath="..\fitz\res_halftone.c"
+				>
+			</File>
+			<File
 				RelativePath="..\fitz\res_path.c"
 				>
 			</File>