分類: Android

『ZLIB』開源『壓縮』同『解壓』程式庫, 支持『DEFLATE』冇損壓縮算法,佢混合『LZ77算法』同『霍夫曼編碼』.

『DEFLATE』壓縮算法冇專利權.畀人大量應用係『網络』『圖檔』『文檔』『影片』.

.PNG/ Libpng	圖檔解壓
.ZIP	壓縮檔
.tar	壓縮檔
.gz	壓縮檔
HTTP	壓縮傅送
FFmpeg	影片解壓

下载『ZLIB』

http://www.zlib.net/

http://www.zlib.net/zlib-1.2.13.tar.gz

『Android studio』內置『ZLIB』, 唔使下載.但要係『CMakeLists.txt』增添『zlib』庫.

CMakeLists.txt文檔
find_library( z-lib z )	搜索zlib
target_link_libraries( ${z-lib} )	連接zlib

包含『ZLIB』頭文檔

#include <zlib.h>	Zlib-api
#include <zconf.h>

『z_stream』壓縮同解壓皆需此結构體

z_stream stream;	zlib流結构體
stream.zalloc = Z_NULL;	NULL用默認記憶體分配函数
stream.zfree  = Z_NULL;	NULL用默認記憶體释放函数
stream.opaque = Z_NULL;
stream.next_in  = (Bytef*)sour;	蒞源
stream.avail_in = (uInt)sour_length;	蒞源長
stream.next_out = dest;	輸出
stream.avail_out = (uInt)*dest_length;	輸出長

『ZLIB』壓縮分叁步

壓縮
deflateInit(&stream, level)	分配記憶體,level壓縮等級
deflate(&stream, flush);	壓縮數據, flush設0
deflateEnd(&stream);	释放記憶體

 

int deflateInit2(	deflateInit()加强版
z_streamp strm,	zlib流結构體
int  level,	level壓縮等級0~9. 0:速度快,唔壓縮. 9:速度慢,壓縮率高.
int  method,	壓縮算法僅支緩Z_DEFLATED
int  windowBits,	處理RAW DEFLATE手法.
int  memLevel,	指定記憶體分配MAX_MEM_LEVEL
int  strategy));	壓縮策略,僅影響壓縮比.默認Z_DEFAULT_STRATEGY

 

level	壓縮等級
#define Z_NO_COMPRESSION         0	唔壓縮
#define Z_BEST_SPEED             1	高速,低壓縮率
#define Z_BEST_COMPRESSION       9	高壓縮率, 慢速
#define Z_DEFAULT_COMPRESSION  (-1)	默認壓縮

 

windowBits	處理RAW DEFLATE手法.
8~15:	純deflate壓縮
-8~-15:	zlib頭 + deflate + zlib尾
> 16:	Gzip頭+ deflate + Gzip尾

 

method	壓縮算法
#define Z_DEFLATED   8	DEFLATE冇損壓縮

 

memLevel	記憶體分配
MemLevel=1	最小記憶體,速度慢壓縮比低
MemLevel=9 #define MAX_MEM_LEVEL 9	最大記憶體,最佳速度
MemLevel=8	默認值

 

strategy	壓縮算法設定
#define Z_FILTERED            1	僅FILTERED生成數據
#define Z_HUFFMAN_ONLY        2	僅霍夫曼編碼
#define Z_RLE                 3	匹配長度=1
#define Z_FIXED               4	禁霍夫曼編碼
#define Z_DEFAULT_STRATEGY    0	默認壓縮設定

『ZLIB』解壓分叁步

解壓
inflateInit(&stream)	分配記憶體
inflate(&stream, Z_NO_FLUSH);	解压數據
inflateEnd(stream);	释放記憶體

 

返回碼
#define Z_OK            0
#define Z_STREAM_END    1	結束
#define Z_NEED_DICT     2	愛密碼
#define Z_ERRNO        (-1)
#define Z_STREAM_ERROR (-2)
#define Z_DATA_ERROR   (-3)	加密數據損壞壞,或缺失.
#define Z_MEM_ERROR    (-4)	唔够記憶體
#define Z_BUF_ERROR    (-5)	唔够緩存
#define Z_VERSION_ERROR (-6)

 

解壓示例

int Uncompress(PBYTE dest,int * dest_length,PBYTE sour,int sour_length)

{

z_stream stream;

int ret;

stream.zalloc = (alloc_func)0;

stream.zfree  = (free_func)0;

stream.opaque = (voidpf)0;

stream.next_in  = (Bytef*)sour;

stream.avail_in = (uInt)sour_length;

stream.next_out = dest;

stream.avail_out = (uInt)*dest_length;

MAX_MEM_LEVEL

ret = inflateInit2(&stream, 16+MAX_WBITS);

if (ret != Z_OK)

return ret;

 

ret = inflate(&stream, Z_NO_FLUSH);// 解压

*dest_length = stream.total_out;

inflateEnd(&stream);

return ret;

}

 

壓缩示例

bool Compress(PBYTE dest,int * dest_length,PBYTE sour,int sour_length, int level)

{

int ret, flush;

int sour_offset,dest_offset;

int have;

z_stream stream;

BYTE in[ZIP_CHUNK];

BYTE out[ZIP_CHUNK];

 

stream.zalloc = Z_NULL;// 内存分配函数

stream.zfree  = Z_NULL;// 内存释放函数

stream.opaque = Z_NULL;

stream.next_in  = (Bytef*)sour;

stream.avail_in = (uInt)sour_length;

stream.next_out = dest;

stream.avail_out = (uInt)*dest_length;

 

ret = deflateInit(&stream, level);// 内存分配

if (ret != Z_OK)

return false;

 

ret = deflate(&stream, flush);  // 进行压缩

*dest_length = stream.total_out;

 

deflateEnd(&stream);// 释放内存

return ret;

}

Android Studio係右下角彈出警示,『Cannot load settings from file』冇法載入『misc.xml』,事實係文檔損毁.內容大致如下.粘貼後諸存.

『misc.xml』文檔

<?xml version=”1.0″ encoding=”UTF-8″?> <project version=”4″> <component name=”ProjectRootManager” version=”2″ languageLevel=”JDK_17″ default=”true” project-jdk-name=”Android Studio default JDK” project-jdk-type=”JavaSDK”> <output url=”file://$PROJECT_DIR$/build/classes” /> </component> <component name=”ProjectType”> <option name=”id” value=”Android” /> </component> </project>

 

Load settings

Cannot load settings from file

“D:\ANDROID\GeomanticCompass\.idea\misc.xml”;illegal character(NULL,Unicode 0) encountered: not valid in any content at[row,col{unknown-source}]:[1,2] Please correct the file content

 

『Android Studio』冇拉拉丟失鍵盤映射『Missing keymap』『Cannot find keymap “Windows Proper Redo” 』.

重新設鍵盤映射.

1. 撳『File』->『Settings』
2. 撳『Keymap』->『Eclipse』
3. 撳『Apply』

Missing keymap

Cannot find keymap “Windows Proper Redo”

Search for Windows Proper Redo Keymap plugin