交叉编译 tesseract
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官方参考资料说明：
tesseract 依赖库: (https://github.com/tesseract-ocr/tesseract/wiki/Compiling#linux)
leptonica 依赖库: ( http://www.leptonica.org/source/README.html )
交叉编译 tesseract
(以 tesseract 3.01 为例)
说明：
1. 嵌入式环境：mips架构， linux 3.08
2. 交叉工具链： mips-linux-gnu-
3.工具链路径： /home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/
一、依赖库：
依赖库: (官方有说明：https://github.com/tesseract-ocr/tesseract/wiki/Compiling#linux)
1. leptonica-1.67
> 其依赖库: (官方说明：http://www.leptonica.org/source/README.html)
(1) libz (建议版本zlib_1.2.3, 实测zlib_1.2.8也可)
(2) libjpeg_9.0 (使tesseract支持jpeg，pbm图片格式)
(3) 如需支持其他图片格式如tif，需要安装其他库libtiif
二、交叉编译 leptonica-1.67
1. 交叉编译 libjpeg_9.0
（1）mkdir tmp
（2）./configure --host=mips-linux-gnu --target=mips-linux-gnu --prefix=$PWD/tmp
CC=mips-linux-gnu-gcc CXX=mips-linux-gnu-g++
CFLAGS=-I/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include
LDFLAGS=-L/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
（3）make -j4
（4）make install
（5）把tmp/下的include头文件和库文件lib复制到
/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include
/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
工具链下
2. mkdir tmp
3. ./configure --host=mips-linux-gnu --target=mips-linux-gnu --prefix=$PWD/tmp
CC=mips-linux-gnu-gcc CXX=mips-linux-gnu-g++
CFLAGS=-I/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include
LDFLAGS=-L/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
--with-jpeg (表示添加jpeg库)
--includedir=/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include
--libdir=/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
其中：
--includedir= 表示头文件安装目录
--libdir= 表示库安装目录
必需配置，否则会找不到库文件，导致编译不通过
4. 链接库环境变量
export LD_LIBRARY_PATH=/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216
:/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
5. make -j4
出现错误：
/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/bin/../lib/gcc/mips-linux-gnu/4.7.2/../../../../mips-linux-gnu/bin/ld: warning: libz.so.1, needed by ./.libs/liblept.so, not found (try using -rpath or -rpath-link)
./.libs/liblept.so: undefined reference to `inflate\'
./.libs/liblept.so: undefined reference to `powf\'
./.libs/liblept.so: undefined reference to `ceil\'
./.libs/liblept.so: undefined reference to `atan2\'
./.libs/liblept.so: undefined reference to `expf\'
./.libs/liblept.so: undefined reference to `deflate\'
./.libs/liblept.so: undefined reference to `floorf\'
./.libs/liblept.so: undefined reference to `deflateInit_\'
./.libs/liblept.so: undefined reference to `sin\'
./.libs/liblept.so: undefined reference to `inflateEnd\'
./.libs/liblept.so: undefined reference to `atan\'
./.libs/liblept.so: undefined reference to `deflateEnd\'
./.libs/liblept.so: undefined reference to `tan\'
./.libs/liblept.so: undefined reference to `inflateInit_\'
./.libs/liblept.so: undefined reference to `cos\'
./.libs/liblept.so: undefined reference to `log\'
./.libs/liblept.so: undefined reference to `sqrt\'
collect2: error: ld returned 1 exit status
原因：找不到libz库，缺少math库
解决：修改 Makefile
对于当前路径下 src/Makefile 和 Makefile:
（1） LIBS =
-> LIBS = -lm
（2） ZLIB_LIBS =
-> ZLIB_LIBS = -lz
（3） LDFLAGS = -L/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/mips-linux-gnu/libc/lib
-L/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
6. make install
7. 把tmp/下的include头文件和库文件lib复制到
/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include
/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
工具链下（如已配置 --includedir --libdir， 则make install时已经安装到以上目录)
三、交叉编译tesseract 3.01
1. ./autogen.sh
2. mkdir tmp
3. ./configure --host=mips-linux-gnu --target=mips-linux-gnu --prefix=$PWD/tmp
CC=mips-linux-gnu-gcc CXX=mips-linux-gnu-g++
CFLAGS=-I/home/newton_linux/prebuilts/toolchains/mips-gcc472- glibc216/include
LDFLAGS=-L/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
报错：
checking for leptonica... configure: error: leptonica not found:
修改为：
./configure --host=mips-linux-gnu --target=mips-linux-gnu --prefix=$PWD/tmp
CC=mips-linux-gnu-gcc CXX=mips-linux-gnu-g++
CFLAGS=-I/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include
LDFLAGS=-L/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
LIBLEPT_HEADERSDIR=/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/include （指定leptonica库路径）
如果再报错：
checking for leptonica... yes
checking for pixCreate in -llept... no
configure: error: leptonica library missing
则删除 configure 文件中的以下内容的带”*“的行
* if test "x$ac_cv_lib_lept_pixCreate" = xyes; then :
cat >>confdefs.h <<_ACEOF
#define HAVE_LIBLEPT 1
_ACEOF
LIBS="-llept $LIBS"
* else
* as_fn_error $? "leptonica library missing" "$LINENO" 5
* fi
4. 链接库环境变量不变
export LD_LIBRARY_PATH=/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216:
/home/newton_linux/prebuilts/toolchains/mips-gcc472-glibc216/lib
5. make -j4
出现错误：
svutil.cpp: In static member function \'static void SVSync::StartProcess(const char*, const char*)\':
svutil.cpp:89:18: error: \'fork\' was not declared in this scope
svutil.cpp:119:28: error: \'execvp\' was not declared in this scope
svutil.cpp: In member function \'void SVNetwork::Close()\':
svutil.cpp:262:16: error: \'close\' was not declared in this scope
svutil.cpp: In constructor \'SVNetwork::SVNetwork(const char*, int)\':
svutil.cpp:417:14: error: \'sleep\' was not declared in this scope
原因：无对应头文件
解决：
svutil.cpp 文件开始出添加头文件： #include <unistd.h>
6. make install
四、开发板上使用tesseract
1. 分别把tesseract、leptonica、libjpeg_9、libz的tmp/下的include头文件和库文件lib复制到开发板/include和/lib目录下
2. 在开发板上设置语言数据路径：
export TESSDATA_PREFIX=/alg
即把语言数据文件放置在/alg/tessdata之下
3. 开发板上执行：
tesseract xxx.jpg out -l eng
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