libpng是什么?
专门对png进行读写,并且要与zlib同时使用Android 使用cmake编译libpng项目地址:
https://github.com/kingdawin/libpng-android
这个项目只需要libpng代码,而不用下载zlib，只需在cmake中关联Android系统的zlib库。由于Android Bitmap解压也用到libpng库，所以系统自身带有zlib。cmake配置相关知识
- 库与库如何关联
使用target_link_libraries()，在里面加入你需要关联的库即可
# png库与zlib关联
target_link_libraries( ${project_name} PUBLIC ZLIB::ZLIB )
- 如何添加多个库
使用add_library
add_library(
#库名
${project_name}
#代码路径
${sources}
${headers} )
项目CMakeList.txt文件说明
cmake_minimum_required( VERSION 3.6 )
# png库名
set( project_name png )
project( ${project_name} )
if( MSVC )
add_definitions(/MP)
endif()
#jni代码路径，根据你实际路径修改
set( source_dir ${CMAKE_CURRENT_SOURCE_DIR}/jni )
#头文件路径
set( headers
${source_dir}/pnginfo.h
${source_dir}/config.h
${source_dir}/png.h
${source_dir}/pngconf.h
${source_dir}/pngdebug.h
${source_dir}/pnglibconf.h
${source_dir}/pngprefix.h
${source_dir}/pngpriv.h
${source_dir}/pngstruct.h
)
# c文件路径
set( sources
${source_dir}/arm/arm_init.c
${source_dir}/arm/filter_neon.S
${source_dir}/arm/filter_neon_intrinsics.c
${source_dir}/png.c
${source_dir}/pngerror.c
${source_dir}/pngget.c
${source_dir}/pngmem.c
${source_dir}/pngpread.c
${source_dir}/pngread.c
${source_dir}/pngrio.c
${source_dir}/pngrtran.c
${source_dir}/pngrutil.c
${source_dir}/pngset.c
${source_dir}/pngtest.c
${source_dir}/pngtrans.c
${source_dir}/pngwio.c
${source_dir}/pngwrite.c
${source_dir}/pngwtran.c
${source_dir}/pngwutil.c
)
# 链接系统的zlib库
find_package( zlib REQUIRED )
# If you want a shared library instead of static, specify the BUILD_SHARED_LIBS
# variable (which is a built-in CMake option).
# 添加libpng库
add_library( ${project_name} ${sources} ${headers} )
# png库与zlib关联
target_link_libraries( ${project_name} PUBLIC ZLIB::ZLIB )
target_include_directories( ${project_name} PUBLIC
$<BUILD_INTERFACE:${source_dir}>
$<INSTALL_INTERFACE:include>
)
#使用add_library可以添加多个库，比如自己定义一个native-jni
#native-jni要使用png lib，只要将png lib关联即可在native-jni代码文件用
# #include<png.h>引用相关函数
add_library(
#你的库名
native-jni
#填你的c/c++代码路径
${sources}
${headers} )
#下面的配置用来安装，可以删除
############################################################
## INSTALL
############################################################
include( CMakePackageConfigHelpers )
set( PNG_VERSION 1.6.29 )
set( PNG_EXPORT_DIR share/png-${PNG_VERSION}/cmake )
set( PNG_EXPORT_NAME png-export )
install( TARGETS png EXPORT ${PNG_EXPORT_NAME}
RUNTIME DESTINATION bin
LIBRARY DESTINATION lib
ARCHIVE DESTINATION lib
INCLUDES DESTINATION include
)
install( FILES ${headers} DESTINATION include )
install( EXPORT ${PNG_EXPORT_NAME} DESTINATION ${PNG_EXPORT_DIR} )
configure_file( png-config.cmake.in png-config.cmake @ONLY )
write_basic_package_version_file(
png-config-version.cmake
VERSION ${PNG_VERSION}
COMPATIBILITY AnyNewerVersion
)
install(
FILES
${CMAKE_CURRENT_BINARY_DIR}/png-config.cmake
${CMAKE_CURRENT_BINARY_DIR}/png-config-version.cmake
DESTINATION ${PNG_EXPORT_DIR}
)
4.NDK环境配置
1）下载LLDB,NDK,CMake
as中打开sdk下载，选择SDK Tools,勾选LLDB任意版本和NDK
image.png
2）设置as的NDK路径
5.在已有的项目添加Cmake文件，并与项目关联
