#include "fitz.h"

fz_halftone *
fz_new_halftone(fz_context *ctx, int comps)
{
	fz_halftone *ht;
	int i;

	ht = fz_malloc(ctx, 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_context *ctx, fz_halftone *ht)
{
	int i;

	if (!ht || --ht->refs != 0)
		return;
	for (i = 0; i < ht->n; i++)
		fz_drop_pixmap(ctx, ht->comp[i]);
	fz_free(ctx, 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(fz_context *ctx, int num_comps)
{
	fz_halftone *ht = fz_new_halftone(ctx, num_comps);
	assert(num_comps == 1); /* Only support 1 component for now */
	ht->comp[0] = fz_new_pixmap_with_data(ctx, NULL, 16, 16, mono_ht);
	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_context *ctx, fz_pixmap *pix, fz_halftone *ht)
{
	fz_bitmap *out;
	unsigned char *ht_line, *o, *p;
	int w, h, x, y, n, pstride, ostride;

	if (pix == NULL || ht == NULL)
		return NULL;

	assert(pix->n == 2); /* Mono + Alpha */

	n = pix->n-1; /* Remove alpha */
	ht_line = fz_malloc(ctx, pix->w * n);
	out = fz_new_bitmap(ctx, pix->w, pix->h, n);
	o = out->samples;
	p = pix->samples;

	h = pix->h;
	x = pix->x;
	y = pix->y;
	w = pix->w;
	ostride = out->stride;
	pstride = pix->w * pix->n;
	while (h--)
	{
		make_ht_line(ht_line, ht, x, y++, w);
		do_threshold_1(ht_line, p, o, w);
		o += ostride;
		p += pstride;
	}
	return out;
}