Replace our custom version of Android.mk with instructions on how to build a libjpeg-turbo SDK for Android using autotools. Upon consulting with AOSP, it appears that Android.mk isn't really necessary except when building libjpeg-turbo for use by the Android platform itself, and it makes more sense for them to maintain the makefile for that purpose rather than for it to be upstreamed. ndk-build has serious limitations that prevent it from being used to generate static libjpeg-turbo libraries (mainly, it isn't possible to combine pre-built objects from one module into a static library for another module, which is necessary because the SIMD extensions sometimes have to be built with different CFLAGS than the rest of the code.) In general, it's just better not to introduce a new build system.

git-svn-id: svn://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1272 632fc199-4ca6-4c93-a231-07263d6284db

1 files changed, 40 insertions, 1 deletions

diff --git a/BUILDING.txt b/BUILDING.txt
index d40c270..13835a1 100644
--- a/BUILDING.txt
+++ b/BUILDING.txt
@@ -319,7 +319,7 @@ This release of libjpeg-turbo can use ARM NEON SIMD instructions to accelerate
 JPEG compression/decompression by approximately 2-4x on ARMv7 and later
 platforms.  If libjpeg-turbo is configured on an ARM Linux platform, then the
 build system will automatically include the NEON SIMD routines, if they are
-supported.
+supported.  Build instructions for other ARM-based platforms follow.
 
 
 Building libjpeg-turbo for iOS
@@ -393,6 +393,45 @@ described above.  Otherwise, you may get a libtool error such as "unable to
 infer tagged configuration."
 
 
+Building libjpeg-turbo for Android
+----------------------------------
+
+Building libjpeg-turbo for Android platforms requires the Android NDK
+(https://developer.android.com/tools/sdk/ndk) and autotools.  The following is
+a general recipe script that can be modified for your specific needs.
+
+  # Set these variables to suit your needs
+  NDK_PATH={full path to the "ndk" directory-- for example, /opt/android/ndk}
+  BUILD_PLATFORM={the platform name for the NDK package you installed--
+    for example, "windows-x86" or "linux-x86_64"}
+  TOOLCHAIN_VERSION={"4.6", "4.8", etc.  This corresponds to a toolchain
+    directory under ${NDK_PATH}/toolchains/.}
+  ANDROID_VERSION={The minimum version of Android to support-- for example,
+    "9", "19", etc.}
+
+  HOST=arm-linux-androideabi
+  TOOLCHAIN=${NDK_PATH}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
+  SYSROOT=${NDK_PATH}/platforms/android-${ANDROID_VERSION}/arch-arm
+  ANDROID_INCLUDES="-I${SYSROOT}/usr/include -I${TOOLCHAIN}/include"
+  ANDROID_CFLAGS="-march=armv7-a -mfloat-abi=softfp -fprefetch-loop-arrays \
+    -fstrict-aliasing --sysroot=${SYSROOT}"
+  export CPP=${TOOLCHAIN}/bin/${HOST}-cpp
+  export AR=${TOOLCHAIN}/bin/${HOST}-ar
+  export AS=${TOOLCHAIN}/bin/${HOST}-as
+  export NM=${TOOLCHAIN}/bin/${HOST}-nm
+  export CC=${TOOLCHAIN}/bin/${HOST}-gcc
+  export LD=${TOOLCHAIN}/bin/${HOST}-ld
+  export RANLIB=${TOOLCHAIN}/bin/${HOST}-ranlib
+  export OBJDUMP=${TOOLCHAIN}/bin/${HOST}-objdump
+  export STRIP=${TOOLCHAIN}/bin/${HOST}-strip
+  cd {build_directory}
+  sh {source_directory}/configure --host=${HOST} \
+    CFLAGS="${ANDROID_INCLUDES} ${ANDROID_CFLAGS} -O3" \
+    CPPFLAGS="${ANDROID_INCLUDES} ${ANDROID_CFLAGS}" \
+    LDFLAGS="${ANDROID_CFLAGS}" --with-simd ${1+"$@"}
+  make
+
+
 *******************************************************************************
 **     Building on Windows (Visual C++ or MinGW)
 *******************************************************************************