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

$

$

)

#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