lavc: add xface image decoder and encoder

Based on libcompface code by James Ashton <James.Ashton@anu.edu.au>, and
relicensed to LGPL with the author's consent.

1 files changed, 95 insertions, 0 deletions

diff --git a/libavcodec/xface.h b/libavcodec/xface.h
new file mode 100644
index 0000000000..cd59ba084a
--- /dev/null
+++ b/libavcodec/xface.h
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 1990 James Ashton - Sydney University
+ * Copyright (c) 2012 Stefano Sabatini
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * X-Face common definitions.
+ */
+
+#include <stdint.h>
+
+/* define the face size - 48x48x1 */
+#define XFACE_WIDTH  48
+#define XFACE_HEIGHT 48
+#define XFACE_PIXELS (XFACE_WIDTH * XFACE_HEIGHT)
+
+/* compressed output uses the full range of printable characters.
+ * In ASCII these are in a contiguous block so we just need to know
+ * the first and last. The total number of printables is needed too. */
+#define XFACE_FIRST_PRINT '!'
+#define XFACE_LAST_PRINT '~'
+#define XFACE_PRINTS (XFACE_LAST_PRINT - XFACE_FIRST_PRINT + 1)
+
+/*
+ * Image is encoded as a big integer, using characters from '~' to
+ * '!', for a total of 92 symbols. In order to express 48x48=2304
+ * bits, we need a total of 354 digits, as given by:
+ * ceil(lg_92(2^2304)) = 354
+ */
+#define XFACE_MAX_DIGITS 354
+
+#define XFACE_BITSPERWORD 8
+#define XFACE_WORDCARRY (1 << XFACE_BITSPERWORD)
+#define XFACE_WORDMASK (XFACE_WORDCARRY - 1)
+
+#define XFACE_MAX_WORDS ((XFACE_PIXELS * 2 + XFACE_BITSPERWORD - 1) / XFACE_BITSPERWORD)
+
+/* Portable, very large unsigned integer arithmetic is needed.
+ * Implementation uses arrays of WORDs. */
+typedef struct {
+    int nb_words;
+    uint8_t words[XFACE_MAX_WORDS];
+} BigInt;
+
+/**
+ * Add a to b storing the result in b.
+ */
+void ff_big_add(BigInt *b, uint8_t a);
+
+/**
+ * Divide b by a storing the result in b and the remainder in the word
+ * pointed to by r.
+ */
+void ff_big_div(BigInt *b, uint8_t a, uint8_t *r);
+
+/**
+ * Multiply a by b storing the result in b.
+ */
+void ff_big_mul(BigInt *b, uint8_t a);
+
+/* Each face is encoded using 9 octrees of 16x16 each. Each level of the
+ * trees has varying probabilities of being white, grey or black.
+ * The table below is based on sampling many faces */
+enum XFaceColor { XFACE_COLOR_BLACK = 0, XFACE_COLOR_GREY, XFACE_COLOR_WHITE };
+
+/* Data of varying probabilities are encoded by a value in the range 0 - 255.
+ * The probability of the data determines the range of possible encodings.
+ * Offset gives the first possible encoding of the range. */
+typedef struct {
+    int range;
+    int offset;
+} ProbRange;
+
+extern const ProbRange ff_xface_probranges_per_level[4][3];
+
+extern const ProbRange ff_xface_probranges_2x2[16];
+
+void ff_xface_generate_face(uint8_t *dst, uint8_t * const src);