From b70ce7de2b8ed37f7bd4fa01bb95b45a79c502e7 Mon Sep 17 00:00:00 2001
From: Sebastian Rasmussen <sebras@gmail.com>
Date: Sat, 24 Sep 2016 16:47:59 +0800
Subject: tiff: Add support for thunder decoding.

---
 include/mupdf/fitz/filter.h  |   1 +
 source/fitz/filter-thunder.c | 153 +++++++++++++++++++++++++++++++++++++++++++
 source/fitz/load-tiff.c      |  13 ++++
 3 files changed, 167 insertions(+)
 create mode 100644 source/fitz/filter-thunder.c

diff --git a/include/mupdf/fitz/filter.h b/include/mupdf/fitz/filter.h
index 5192540e..58dc3e21 100644
--- a/include/mupdf/fitz/filter.h
+++ b/include/mupdf/fitz/filter.h
@@ -34,5 +34,6 @@ void fz_drop_jbig2_globals_imp(fz_context *ctx, fz_storable *globals);
 fz_stream *fz_open_sgilog16(fz_context *ctx, fz_stream *chain, int w);
 fz_stream *fz_open_sgilog24(fz_context *ctx, fz_stream *chain, int w);
 fz_stream *fz_open_sgilog32(fz_context *ctx, fz_stream *chain, int w);
+fz_stream *fz_open_thunder(fz_context *ctx, fz_stream *chain, int w);
 
 #endif
diff --git a/source/fitz/filter-thunder.c b/source/fitz/filter-thunder.c
new file mode 100644
index 00000000..65cb115b
--- /dev/null
+++ b/source/fitz/filter-thunder.c
@@ -0,0 +1,153 @@
+#include "mupdf/fitz/system.h"
+#include "mupdf/fitz/context.h"
+#include "mupdf/fitz/stream.h"
+
+/* 4bit greyscale Thunderscan decoding */
+
+typedef struct fz_thunder_s fz_thunder;
+
+struct fz_thunder_s
+{
+	fz_stream *chain;
+	int lastpixel;
+	int run;
+	int pixel;
+
+	int len;
+	unsigned char *buffer;
+};
+
+static int
+next_thunder(fz_context *ctx, fz_stream *stm, size_t max)
+{
+	fz_thunder *state = stm->state;
+	unsigned char *p = state->buffer;
+	unsigned char *ep;
+	int c, v, i, pixels, index;
+
+	if (max > state->len);
+		max = state->len;
+
+	ep = p + max;
+
+	c = 0;
+	while (p < ep && c >= 0)
+	{
+		pixels = 0;
+		v = 0;
+
+		while (pixels < 2)
+		{
+			if (state->run > 0)
+			{
+				v <<= 4;
+				v |= state->pixel & 0xf;
+				state->pixel >>= 4;
+				state->run--;
+				pixels++;
+
+				if (state->run > 2)
+					state->pixel |= ((state->pixel >> 4) & 0xf) << 8;
+			}
+			else
+			{
+				c = fz_read_byte(ctx, state->chain);
+				if (c < 0)
+					break;
+
+				switch ((c >> 6) & 0x3)
+				{
+				case 0x0: /* run of pixels identical to last pixel */
+					state->run = c;
+					state->pixel = (state->lastpixel << 8) | (state->lastpixel << 4) | (state->lastpixel << 0);
+					break;
+
+				case 0x1: /* three pixels with 2bit deltas to last pixel */
+					for (i = 0; i < 3; i++)
+					{
+						static const int deltas[] = { 0, 1, 0, -1 };
+						index = (c >> (4 - i * 2)) & 0x3;
+						if (index == 2)
+							continue;
+
+						state->lastpixel = (state->lastpixel + deltas[index]) & 0xf;
+						state->pixel <<= 4;
+						state->pixel |= state->lastpixel;
+						state->run++;
+					}
+					break;
+
+				case 0x2: /* two pixels with 3bit deltas to last pixel */
+					for (i = 0; i < 2; i++)
+					{
+						static const int deltas[] = { 0, 1, 2, 3, 0, -3, -2, -1 };
+						index = (c >> (3 - i * 3)) & 0x7;
+						if (index == 4)
+							continue;
+
+						state->lastpixel = (state->lastpixel + deltas[index]) & 0xf;
+						state->pixel <<= 4;
+						state->pixel |= state->lastpixel;
+						state->run++;
+					}
+					break;
+
+				case 0x3: /* a single raw 4bit pixel */
+					state->run = 1;
+					state->pixel = c & 0xf;
+					state->lastpixel = state->pixel & 0xf;
+					break;
+				}
+			}
+		}
+
+		if (pixels)
+			*p++ = v;
+	}
+
+	stm->rp = state->buffer;
+	stm->wp = p;
+	stm->pos += p - state->buffer;
+
+	if (stm->rp != p)
+		return *stm->rp++;
+	return EOF;
+}
+
+static void
+close_thunder(fz_context *ctx, void *state_)
+{
+	fz_thunder *state = (fz_thunder *)state_;
+	fz_stream *chain = state->chain;
+
+	fz_free(ctx, state->buffer);
+	fz_free(ctx, state);
+	fz_drop_stream(ctx, chain);
+}
+
+fz_stream *
+fz_open_thunder(fz_context *ctx, fz_stream *chain, int w)
+{
+	fz_thunder *state = NULL;
+
+	fz_var(state);
+
+	fz_try(ctx)
+	{
+		state = fz_malloc_struct(ctx, fz_thunder);
+		state->chain = chain;
+		state->run = 0;
+		state->pixel = 0;
+		state->lastpixel = 0;
+		state->len = w / 2;
+		state->buffer = fz_malloc(ctx, state->len);
+	}
+	fz_catch(ctx)
+	{
+		fz_free(ctx, state);
+		fz_drop_stream(ctx, chain);
+		fz_rethrow(ctx);
+	}
+
+	return fz_new_stream(ctx, state, next_thunder, close_thunder);
+}
diff --git a/source/fitz/load-tiff.c b/source/fitz/load-tiff.c
index b57497a2..87e350f0 100644
--- a/source/fitz/load-tiff.c
+++ b/source/fitz/load-tiff.c
@@ -170,6 +170,14 @@ fz_decode_tiff_sgilog24(fz_context *ctx, struct tiff *tiff, fz_stream *chain, un
 	fz_drop_stream(ctx, stm);
 }
 
+static void
+fz_decode_tiff_thunder(fz_context *ctx, struct tiff *tiff, fz_stream *chain, unsigned char *wp, int wlen, int w)
+{
+	fz_stream *stm = fz_open_thunder(ctx, chain, w);
+	fz_read(ctx, stm, wp, wlen);
+	fz_drop_stream(ctx, stm);
+}
+
 static void
 fz_decode_tiff_sgilog32(fz_context *ctx, struct tiff *tiff, fz_stream *chain, unsigned char *wp, int wlen, int w)
 {
@@ -518,6 +526,11 @@ fz_decode_tiff_strips(fz_context *ctx, struct tiff *tiff)
 		case 34677:
 			fz_decode_tiff_sgilog24(ctx, tiff, stm, wp, wlen, tiff->imagewidth);
 			break;
+		case 32809:
+			if (tiff->bitspersample != 4)
+				fz_throw(ctx, FZ_ERROR_GENERIC, "invalid bits per pixel in thunder encoding");
+			fz_decode_tiff_thunder(ctx, tiff, stm, wp, wlen, tiff->imagewidth);
+			break;
 		default:
 			fz_throw(ctx, FZ_ERROR_GENERIC, "unknown TIFF compression: %d", tiff->compression);
 		}
-- 
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