ubuntu 18.04 交叉编译opecv 树莓派4 问题总结

最近有需要使用ubuntu  树莓派4 交叉编译OPENCV，编译并不顺利，搞了好久才搞好，感谢各路前人的成果走过的路，没有他们踩过的坑，我们要想编译成功，简直是比登天还难。

坑1：

/home/li/raspi/opencv-4.1.1/3rdparty/libpng/pngstruct.h:30:10: fatal error: zlib.h: No such file or directory
 #include "zlib.h"
          ^~~~~~~~
compilation terminated.
3rdparty/libpng/CMakeFiles/libpng.dir/build.make:62: recipe for target '3rdparty/libpng/CMakeFiles/libpng.dir/png.c.o' failed

zlib.h没有找到，打开opencv-4.1.1/3rdparty/libpng，里面确实没有这个，然后搜索一下本机上有，就把zlib.h复制到里面即可。然后把libtiff那个文件夹也复制一个，因为勾选了编译png和tiff，他们都需要这个

坑2：

in file included from /home/li/raspi/opencv-4.1.1/3rdparty/libtiff/tif_zip.c:48:0:
/home/li/raspi/opencv-4.1.1/3rdparty/libtiff/zlib.h:34:10: fatal error: zconf.h: No such file or directory
 #include "zconf.h"

同上。

坑3：这个坑填了，以上两个坑可能不存在了，因为是可能这个坑导致了上面的，是我没有勾选BUILD_ZLIB，他的意思使用的zlib是x86上的，格式不认，需要勾上BUILD_ZLIB。

[ 61%] Linking CXX shared library ../../lib/libopencv_world.so
/usr/lib32/libz.so: error adding symbols: File in wrong format
collect2: error: ld returned 1 exit status
modules/world/CMakeFiles/opencv_world.dir/build.make:8877: recipe for target 'lib/libopencv_world.so.4.1.1' failed

坑4：莫名其妙的东西

[ 95%] Linking CXX executable ../../bin/opencv_perf_gapi
[ 95%] Built target opencv_perf_gapi
[ 95%] Linking CXX executable ../../bin/opencv_test_core
[ 95%] Built target opencv_test_core
Makefile:162: recipe for target 'all' failed
把有关test的去掉，我去掉了BUILD_opencv_stitching,BUILD_opencv_python_tests,BUILD_opencv_ts

还有其它坑，忘记记录了