a WebP encoder

converts PNG & JPEG to WebP

This is an experimental early version, with lot of room
of later optimizations in both speed and quality.

Compile with the usual `./configure && make`
Command line example is examples/cwebp

Usage:

   cwebp [options] -q quality input.png -o output.webp

where 'quality' is between 0 (poor) to 100 (very good).
Typical value is around 80.

More encoding options with 'cwebp -longhelp'

Change-Id: I577a94f6f622a0c44bdfa9daf1086ace89d45539

src/enc/cost.h

@@ -0,0 +1,52 @@
+// Copyright 2011 Google Inc.
+//
+// This code is licensed under the same terms as WebM:
+//  Software License Agreement:  http://www.webmproject.org/license/software/
+//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
+// -----------------------------------------------------------------------------
+//
+// Cost tables for level and modes.
+//
+// Author: Skal (pascal.massimino@gmail.com)
+
+#ifndef WEBP_ENC_COST_H_
+#define WEBP_ENC_COST_H_
+
+#include "vp8enci.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+extern const uint16_t VP8LevelFixedCosts[2048];   // approximate cost per level
+extern const uint16_t VP8EntropyCost[256];        // 8bit fixed-point log(p)
+
+// Cost of coding one event with probability 'proba'.
+static inline int VP8BitCost(int bit, uint8_t proba) {
+  return !bit ? VP8EntropyCost[proba] : VP8EntropyCost[255 - proba];
+}
+
+// Cost of coding 'nb' 1's and 'total-nb' 0's using 'proba' probability.
+static inline uint64_t VP8BranchCost(uint64_t nb, uint64_t total, uint8_t proba) {
+  return nb * VP8BitCost(1, proba) + (total - nb) * VP8BitCost(0, proba);
+}
+
+// Level cost calculations
+void VP8CalculateLevelCosts(VP8Proba* const proba);
+static inline int VP8LevelCost(const uint16_t* const table, int level) {
+  return VP8LevelFixedCosts[level]
+       + table[level > MAX_VARIABLE_LEVEL ? MAX_VARIABLE_LEVEL : level];
+}
+
+// Mode costs
+extern const uint16_t VP8FixedCostsUV[4];
+extern const uint16_t VP8FixedCostsI16[4];
+extern const uint16_t VP8FixedCostsI4[NUM_BMODES][NUM_BMODES][NUM_BMODES];
+
+//-----------------------------------------------------------------------------
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}    // extern "C"
+#endif
+
+#endif  // WEBP_ENC_COST_H_