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Diffstat (limited to 'drivers/webpold/enc/backward_references.h')
| -rw-r--r-- | drivers/webpold/enc/backward_references.h | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/drivers/webpold/enc/backward_references.h b/drivers/webpold/enc/backward_references.h new file mode 100644 index 0000000000..8006a56ba1 --- /dev/null +++ b/drivers/webpold/enc/backward_references.h @@ -0,0 +1,212 @@ +// Copyright 2012 Google Inc. All Rights Reserved. +// +// 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/ +// ----------------------------------------------------------------------------- +// +// Author: Jyrki Alakuijala (jyrki@google.com) +// + +#ifndef WEBP_ENC_BACKWARD_REFERENCES_H_ +#define WEBP_ENC_BACKWARD_REFERENCES_H_ + +#include <assert.h> +#include <stdlib.h> +#include "../types.h" +#include "../format_constants.h" + +#if defined(__cplusplus) || defined(c_plusplus) +extern "C" { +#endif + +// The spec allows 11, we use 9 bits to reduce memory consumption in encoding. +// Having 9 instead of 11 only removes about 0.25 % of compression density. +#define MAX_COLOR_CACHE_BITS 9 + +// Max ever number of codes we'll use: +#define PIX_OR_COPY_CODES_MAX \ + (NUM_LITERAL_CODES + NUM_LENGTH_CODES + (1 << MAX_COLOR_CACHE_BITS)) + +// ----------------------------------------------------------------------------- +// PrefixEncode() + +// use GNU builtins where available. +#if defined(__GNUC__) && \ + ((__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || __GNUC__ >= 4) +static WEBP_INLINE int BitsLog2Floor(uint32_t n) { + return n == 0 ? -1 : 31 ^ __builtin_clz(n); +} +#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_IX86)) +#include <intrin.h> +#pragma intrinsic(_BitScanReverse) + +static WEBP_INLINE int BitsLog2Floor(uint32_t n) { + unsigned long first_set_bit; + return _BitScanReverse(&first_set_bit, n) ? first_set_bit : -1; +} +#else +static WEBP_INLINE int BitsLog2Floor(uint32_t n) { + int log = 0; + uint32_t value = n; + int i; + + if (value == 0) return -1; + for (i = 4; i >= 0; --i) { + const int shift = (1 << i); + const uint32_t x = value >> shift; + if (x != 0) { + value = x; + log += shift; + } + } + return log; +} +#endif + +static WEBP_INLINE int VP8LBitsLog2Ceiling(uint32_t n) { + const int floor = BitsLog2Floor(n); + if (n == (n & ~(n - 1))) // zero or a power of two. + return floor; + else + return floor + 1; +} + +// Splitting of distance and length codes into prefixes and +// extra bits. The prefixes are encoded with an entropy code +// while the extra bits are stored just as normal bits. +static WEBP_INLINE void PrefixEncode(int distance, int* const code, + int* const extra_bits_count, + int* const extra_bits_value) { + // Collect the two most significant bits where the highest bit is 1. + const int highest_bit = BitsLog2Floor(--distance); + // & 0x3f is to make behavior well defined when highest_bit + // does not exist or is the least significant bit. + const int second_highest_bit = + (distance >> ((highest_bit - 1) & 0x3f)) & 1; + *extra_bits_count = (highest_bit > 0) ? (highest_bit - 1) : 0; + *extra_bits_value = distance & ((1 << *extra_bits_count) - 1); + *code = (highest_bit > 0) ? (2 * highest_bit + second_highest_bit) + : (highest_bit == 0) ? 1 : 0; +} + +// ----------------------------------------------------------------------------- +// PixOrCopy + +enum Mode { + kLiteral, + kCacheIdx, + kCopy, + kNone +}; + +typedef struct { + // mode as uint8_t to make the memory layout to be exactly 8 bytes. + uint8_t mode; + uint16_t len; + uint32_t argb_or_distance; +} PixOrCopy; + +static WEBP_INLINE PixOrCopy PixOrCopyCreateCopy(uint32_t distance, + uint16_t len) { + PixOrCopy retval; + retval.mode = kCopy; + retval.argb_or_distance = distance; + retval.len = len; + return retval; +} + +static WEBP_INLINE PixOrCopy PixOrCopyCreateCacheIdx(int idx) { + PixOrCopy retval; + assert(idx >= 0); + assert(idx < (1 << MAX_COLOR_CACHE_BITS)); + retval.mode = kCacheIdx; + retval.argb_or_distance = idx; + retval.len = 1; + return retval; +} + +static WEBP_INLINE PixOrCopy PixOrCopyCreateLiteral(uint32_t argb) { + PixOrCopy retval; + retval.mode = kLiteral; + retval.argb_or_distance = argb; + retval.len = 1; + return retval; +} + +static WEBP_INLINE int PixOrCopyIsLiteral(const PixOrCopy* const p) { + return (p->mode == kLiteral); +} + +static WEBP_INLINE int PixOrCopyIsCacheIdx(const PixOrCopy* const p) { + return (p->mode == kCacheIdx); +} + +static WEBP_INLINE int PixOrCopyIsCopy(const PixOrCopy* const p) { + return (p->mode == kCopy); +} + +static WEBP_INLINE uint32_t PixOrCopyLiteral(const PixOrCopy* const p, + int component) { + assert(p->mode == kLiteral); + return (p->argb_or_distance >> (component * 8)) & 0xff; +} + +static WEBP_INLINE uint32_t PixOrCopyLength(const PixOrCopy* const p) { + return p->len; +} + +static WEBP_INLINE uint32_t PixOrCopyArgb(const PixOrCopy* const p) { + assert(p->mode == kLiteral); + return p->argb_or_distance; +} + +static WEBP_INLINE uint32_t PixOrCopyCacheIdx(const PixOrCopy* const p) { + assert(p->mode == kCacheIdx); + assert(p->argb_or_distance < (1U << MAX_COLOR_CACHE_BITS)); + return p->argb_or_distance; +} + +static WEBP_INLINE uint32_t PixOrCopyDistance(const PixOrCopy* const p) { + assert(p->mode == kCopy); + return p->argb_or_distance; +} + +// ----------------------------------------------------------------------------- +// VP8LBackwardRefs + +typedef struct { + PixOrCopy* refs; + int size; // currently used + int max_size; // maximum capacity +} VP8LBackwardRefs; + +// Initialize the object. Must be called first. 'refs' can be NULL. +void VP8LInitBackwardRefs(VP8LBackwardRefs* const refs); + +// Release memory and re-initialize the object. 'refs' can be NULL. +void VP8LClearBackwardRefs(VP8LBackwardRefs* const refs); + +// Allocate 'max_size' references. Returns false in case of memory error. +int VP8LBackwardRefsAlloc(VP8LBackwardRefs* const refs, int max_size); + +// ----------------------------------------------------------------------------- +// Main entry points + +// Evaluates best possible backward references for specified quality. +// Further optimize for 2D locality if use_2d_locality flag is set. +int VP8LGetBackwardReferences(int width, int height, + const uint32_t* const argb, + int quality, int cache_bits, int use_2d_locality, + VP8LBackwardRefs* const best); + +// Produce an estimate for a good color cache size for the image. +int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb, + int xsize, int ysize, + int* const best_cache_bits); + +#if defined(__cplusplus) || defined(c_plusplus) +} +#endif + +#endif // WEBP_ENC_BACKWARD_REFERENCES_H_ |