JPG Image size reducer. How to reduce jpg to desired size without changing resolution on PC and Android?

When we click a photo it contains lot of colors which our eyes cannot differentiate. Higher colors means higher image size and with evolving camera chips images are getting bigger and bigger in size. There are many methods to reduce photo size. Lets look at some methods of reducing image size.


I recently backup my images on Google drive. The images were bigger in size and were in GBs in size which i reduced to ~700MB (deleted few repeated images). Among size reduction methods most of us reduce the image resolution i.e. number of pixels are reduced. For example Full HD images are reduced to qHD or 720p. But i didn't reduced the number of pixels but number of colors!


This is already a reduced image of size ~900KB. I captured this image in my garden in 2016 summer using my Nubia Z9 mini phone. Its already reduced in size to load faster on website.

 

Original: 942KB

 Half resolution: 711KB

Reduced Colors: 268KB

Looking at images its clear that reducing number of colors has greater size reduction than reducing resolution only. Do check the images by downloading them and zoom. Decide yourself which one is better!

Now coming to the tools used for size reduction. Without taking much time below are some tools to reduce size of jpg.

• ImageMagick's convert tool. This s a commandline tool which can reduce jpg size to desired size. Example: convert -define jpeg:extent=500kb nubia_bks_camera.jpg out.jpg. This will reduce original image to ~500KB without changing resolution.
• jpegoptim: this tool is same as imagemagick with desired jpg size.
• IrfanView. This is a windows only GUI software which can reduce jpg files to desired size.

I have created my own Android app which can do above size reduction and is very easy to work with. Here is the link to my app Jpg Image Size Reducer: https://play.google.com/store/apps/details?id=org.greh.imagesizereducer. A quick usage example of this app is you share your selfie which is 2MB and want to reduce size quickly without editing the image. Share it with any image app and select jpg image size reducer and reduce to whatever % or KB and then share the copy to wherever you want!. It can also reduce many files in batch. Its also an image converter and can convert non-jpg files to jpg and reduce its size.



The software above reduce number of colors which reduces size of image even more than reducing size does. However Using both methods can give very small size images. Reducing total colors to few thousand or hundreds can be noticed easily by zooming. Another method to reduce image size is to change image mode to INDEXED from RGB. Indexed mode means all colors are collected at a place/table and index/position of a color from table is used. This can reduce size. However this is not always better.

WildMidi for Android: Compiling WildMidi using Android NDK rev 13

Android had no standard midi protocol before Marshmallow. Even after a standard MIDI event API for a developer to build android app which does midi synthesis by itself is a great feature!. In 2016 i compiled FluidSynth 1.6 for Android and created a SoundFont Midi Player with USB keyboard support. This app can play midi, rmi files and can send midi events via USB MIDI Keyboard, Normal USB keyboard to fluidsynth to synthesize sound. Due to latency and high CPU consumption issues i decided to look at other options. One good option was WildMidi.


WildMidi - https://www.mindwerks.net/projects/wildmidi/


It says -

"The WildMIDI library uses Gravis Ultrasound patch files to convert MIDI files into audio which is then passed back to the calling application for further processing or output

Library Features

• RIFF MIDI file support
• MIDI format 0, 1 and 2 support
• MIDI-like formats: KAR, HMI, HMP, MUS and XMI
• Cross Platform: Linux, Windows, OSX, FreeBSD and etc.
• Thread safe
• host-Endian native streaming
• WAV file output
• Linear and gauss re-sampling
• Final output reverb engine
• Timidity.cfg compatibility

Player Features

• OSS and Alsa Output (Linux/FreeBSD)
• Windows Sound System support (Windows)
• OpenAL (OSX/Others)
• SoundBlaster 16 (DOS)"

In Player features Android sound system is not mentioned and that doesn't mean it cannot be used in Android. I compiled WildMidi for Android and the link to download the binary package is mentioned later in this page. I tested WildMidi on Ubuntu-Studio which had inbuilt "FreePats". The Gravis Ultrasound Patch files are used by WildMidi to synthesize sound. We can use WildMidi player to play midi files on Android by modifying its player code by sending PCM buffer to Android OpenSLES or AudioTrack.

Can wildmidi be used for sending MIDI events to build piano like app with fast response? Currently NO as per wildmidi source!


Looking at source code of wildmidi inside wildmidi_lib.h. It says "Not Yet Implemented". That "latency" thing! everywhere.

Preview:

/* NOTE: Not Yet Implemented Or Tested Properly */
/* Due to delay in audio output in the player, this is not being developed
   futher at the moment. Further Development will occur when output latency
   has been reduced enough to "appear" instant.
WM_SYMBOL int WildMidi_Live (midi * handle, uint32_t midi_event);
 */

/* reserved for future coding
 * need to change these to use a time for cmd_pos and new_cmd_pos

WM_SYMBOL int WildMidi_InsertMidiEvent (midi * handle, uint8_t char midi_cmd, *char midi_cmd_data, unsigned long int midi_cmd_data_size, unsigned long int *cmd_pos);
WM_SYMBOL int WildMidi_DeleteMidiEvent (midi * handle, uint8_t char midi_cmd, unsigned long int *cmd_pos);
WM_SYMBOL int WildMidi_MoveMidiEvent (midi * handle, , uint8_t char midi_cmd, unsigned long int *cmd_pos, unsigned long int *new_cmd_pos);
 */

This can be used to build a midi player for android using wildmidi synthesizer. The build script is same as libpng build script mentioned on my other article.



Download wildmidi arm binary from here:
https://github.com/bindeshkumarsingh/android-native-libs

NEW: Building libpng 1.6.28 using Android NDK r13 CMake based build system

I recently updated to NDK revision 13 and also found ndk samples are now cmake + ninja based. Today 3-4 hours were consumed while trying to compile libpng but finally done it after editing CMakeLists.txt of libpng.

I tried to build libpng using Androud Studio's Gradle plugin from IDE but that was more problematic as it too required CMakeLists.txt editing and kept throwing bad link to libpng.so error. I decided to use shell which is my 1st and last choice to work in most cases. Before putting the scripts/code lets setup our work directory and data and also look at how cmake based build system compiles libpng.


Before starting ensure below tools are installed and working correctly on your system.

• Android NDK revision 12+ is installed. If you have Android SDK installed but NDK is at some other location then you can move NDK inside SDK and rename it to ndk-bundle Or create a sym-link "ndk-bundle" in SDK pointing to actual NDK. After this NDK will start showing in the Android Studio 2.2+ SDK manager.
• Install cmake from SDK manager. It will get extracted in Android SDK directory.
• A good command shell. I use Ubuntu-Studio Linux with bash shell(s). Windows users can use cmd.exe or bash shell through UnixUtils.

Build process:

1. Dowload libpng 1.6.28 from here http://ftp.osuosl.org/pub/blfs/conglomeration/libpng/libpng-1.6.28.tar.xz and extract to some location with shorter path without spaces. e.g. /home/username/projects/libpng in Linux or c:\work\libpng in windows. This is for convenience and avoid space related issues while compiling.
2. Copy full path of android.toolchain.cmake present in NDK. Example /media/bindesh/WORK/SDK_IDE/android-ndk-r13b/build/cmake/android.toolchain.cmake. There is same named file present in ANDROID_SDK/cmake/ like this /media/bindesh/WORK/SDK_IDE/android-sdk-linux-windows/cmake/3.6.3155560/android.toolchain.cmake but we must use toolchain file present in NDK. If toolchain present in sdk/cmake is used incompatibility issues like "Invalid Android NDK revision (should be 12" can occur.
3. Open libpng/CMakeLists.txt file in text editor and add include("/home/bindesh/bin/ndk/build/cmake/android.toolchain.cmake") line after project(libpng C). Change the NDK path to yours.

Copy below bash script to create a file build.sh in libpng folder. Change the cmake, ninja, toolchain, sdk, ndk paths in script and run to build libpng. Replace the toolchain path copied through above steps. I have not tested this on Windows but using UnixUtils's sh.exe it should work.

build script:

#!/bin/sh

# run this script after changing the paths of ndk, sdk, cmake, ninja etc to build libpng or other cmake based library.
# Don't forget to add below line in main CMakeLists.txt after project() line of code.
# include("PATH_TO_NDK/build/cmake/android.toolchain.cmake")

clear
reset

# clean previous files
rm CMakeCache.txt


# Change these paths and run this script to build libpng
ANDROID_NDK_PATH=/home/bindesh/bin/ndk
ANDROID_SDK_PATH=/home/bindesh/bin/android-sdk
ANDROID_NDK=${ANDROID_NDK_PATH}

ANDROID_CMAKE_PATH=${ANDROID_SDK_PATH}/cmake/3.6.3155560/bin
ANDROID_CMAKE_TOOLCHAIN=${ANDROID_NDK_PATH}/build/cmake/android.toolchain.cmake

# Don't use toolchain from cmake
#ANDROID_CMAKE_TOOLCHAIN=/media/bindesh/WORK/SDK_IDE/android-sdk-linux-windows/cmake/3.6.3155560/android.toolchain.cmake


ANDROID_API=9
ANDROID_ARCH=arm
ANDROID_ABI=armeabi-v7a
ANDROID_PLATFORM=android-${ANDROID_API}
ANDROID_ARCH=arch-${ANDROID_ARCH}

${ANDROID_CMAKE_PATH}/cmake -DCMAKE_TOOLCHAIN_FILE=${ANDROID_CMAKE_TOOLCHAIN} -DANDROID_ABI=${ANDROID_ABI} -DANDROID_TOOLCHAIN=gcc -DANDROID_NATIVE_API_LEVEL=${ANDROID_API} -DANDROID_PLATFORM=${ANDROID_PLATFORM} -DCMAKE_MAKE_PROGRAM=${ANDROID_CMAKE_PATH}/ninja -G"Android Gradle - Ninja" 
#-DCMAKE_BUILD_TYPE=Release

#${ANDROID_CMAKE_PATH}/cmake -DCMAKE_TOOLCHAIN_FILE=${ANDROID_CMAKE_TOOLCHAIN} -DCMAKE_MAKE_PROGRAM=${ANDROID_CMAKE_PATH}/ninja -G"Android Gradle - Ninja" -DANDROID_NDK=${ANDROID_NDK}
${ANDROID_CMAKE_PATH}/ninja
#make 

mv ./libpng16.a ./libpng16-${ANDROID_ABI}.a

 


Below is the CMakeOutput.log to check details of build environment.

Preview:

The target system is: Android - 9 - armv7-a
The host system is: Linux - 4.8.0-22-lowlatency - x86_64
Compiling the C compiler identification source file "CMakeCCompilerId.c" succeeded.
Compiler: /home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc 
Build flags: -g;-DANDROID;-ffunction-sections;-funwind-tables;-fstack-protector-strong;-no-canonical-prefixes;-march=armv7-a;-mfloat-abi=softfp;-mfpu=vfpv3-d16;-mthumb;-Wa,--noexecstack;-Wformat;-Werror=format-security;-g;-DANDROID;-ffunction-sections;-funwind-tables;-fstack-protector-strong;-no-canonical-prefixes;-march=armv7-a;-mfloat-abi=softfp;-mfpu=vfpv3-d16;-mthumb;-Wa,--noexecstack;-Wformat;-Werror=format-security;
Id flags: -c

The output was:
0


Compilation of the C compiler identification source "CMakeCCompilerId.c" produced "CMakeCCompilerId.o"

The C compiler identification is GNU, found in "/media/bindesh/WORK/00_write/libpng-1.6.28/CMakeFiles/3.6.0-rc2/CompilerIdC/CMakeCCompilerId.o"

Determining if the C compiler works passed with the following output:
Change Dir: /media/bindesh/WORK/00_write/libpng-1.6.28/CMakeFiles/CMakeTmp

Run Build Command:"/home/bindesh/bin/android-sdk/cmake/3.6.3155560/bin/ninja" "cmTC_76f0a"
[1/2] Building C object CMakeFiles/cmTC_76f0a.dir/testCCompiler.c.o
[2/2] Linking C executable cmTC_76f0a


Detecting C compiler ABI info compiled with the following output:
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Target: arm-linux-androideabi
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  link line: [ /home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../libexec/gcc/arm-linux-androideabi/4.9.x/collect2 -plugin /home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../libexec/gcc/arm-linux-androideabi/4.9.x/liblto_plugin.so -plugin-opt=/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../libexec/gcc/arm-linux-androideabi/4.9.x/lto-wrapper -plugin-opt=-fresolution=/tmp/ccNet1nu.res -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-ldl -plugin-opt=-pass-through=-lgcc --sysroot=/home/bindesh/bin/ndk/platforms/android-9/arch-arm --eh-frame-hdr -dynamic-linker /system/bin/linker -X -m armelf_linux_eabi -z noexecstack -z relro -z now -o cmTC_7ad81 /home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib/crtbegin_dynamic.o -L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/armv7-a/thumb -L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib/armv7-a/thumb -L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x -L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc -L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib -L/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib --build-id --warn-shared-textrel --fatal-warnings --fix-cortex-a8 --no-undefined -z noexecstack -z relro -z now --gc-sections -z nocopyreloc CMakeFiles/cmTC_7ad81.dir/CMakeCCompilerABI.c.o -lgcc -lc -ldl -lgcc /home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib/crtend_android.o]
    arg [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../libexec/gcc/arm-linux-androideabi/4.9.x/collect2] ==> ignore
    arg [-plugin] ==> ignore
    arg [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../libexec/gcc/arm-linux-androideabi/4.9.x/liblto_plugin.so] ==> ignore
    arg [-plugin-opt=/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../libexec/gcc/arm-linux-androideabi/4.9.x/lto-wrapper] ==> ignore
    arg [-plugin-opt=-fresolution=/tmp/ccNet1nu.res] ==> ignore
    arg [-plugin-opt=-pass-through=-lgcc] ==> ignore
    arg [-plugin-opt=-pass-through=-lc] ==> ignore
    arg [-plugin-opt=-pass-through=-ldl] ==> ignore
    arg [-plugin-opt=-pass-through=-lgcc] ==> ignore
    arg [--sysroot=/home/bindesh/bin/ndk/platforms/android-9/arch-arm] ==> ignore
    arg [--eh-frame-hdr] ==> ignore
    arg [-dynamic-linker] ==> ignore
    arg [/system/bin/linker] ==> ignore
    arg [-X] ==> ignore
    arg [-m] ==> ignore
    arg [armelf_linux_eabi] ==> ignore
    arg [-znoexecstack] ==> ignore
    arg [-zrelro] ==> ignore
    arg [-znow] ==> ignore
    arg [-o] ==> ignore
    arg [cmTC_7ad81] ==> ignore
    arg [/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib/crtbegin_dynamic.o] ==> ignore
    arg [-L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/armv7-a/thumb] ==> dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/armv7-a/thumb]
    arg [-L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib/armv7-a/thumb] ==> dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib/armv7-a/thumb]
    arg [-L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x] ==> dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x]
    arg [-L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc] ==> dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc]
    arg [-L/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib] ==> dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib]
    arg [-L/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib] ==> dir [/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib]
    arg [--build-id] ==> ignore
    arg [--warn-shared-textrel] ==> ignore
    arg [--fatal-warnings] ==> ignore
    arg [--fix-cortex-a8] ==> ignore
    arg [--no-undefined] ==> ignore
    arg [-znoexecstack] ==> ignore
    arg [-zrelro] ==> ignore
    arg [-znow] ==> ignore
    arg [--gc-sections] ==> ignore
    arg [-znocopyreloc] ==> ignore
    arg [CMakeFiles/cmTC_7ad81.dir/CMakeCCompilerABI.c.o] ==> ignore
    arg [-lgcc] ==> lib [gcc]
    arg [-lc] ==> lib [c]
    arg [-ldl] ==> lib [dl]
    arg [-lgcc] ==> lib [gcc]
    arg [/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib/crtend_android.o] ==> ignore
  remove lib [gcc]
  remove lib [gcc]
  collapse library dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/armv7-a/thumb] ==> [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/armv7-a/thumb]
  collapse library dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib/armv7-a/thumb] ==> [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/arm-linux-androideabi/lib/armv7-a/thumb]
  collapse library dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x] ==> [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x]
  collapse library dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc] ==> [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc]
  collapse library dir [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/lib] ==> [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/arm-linux-androideabi/lib]
  collapse library dir [/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib] ==> [/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib]
  implicit libs: [c;dl]
  implicit dirs: [/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/armv7-a/thumb;/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/arm-linux-androideabi/lib/armv7-a/thumb;/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x;/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc;/home/bindesh/bin/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/arm-linux-androideabi/lib;/home/bindesh/bin/ndk/platforms/android-9/arch-arm/usr/lib]
  implicit fwks: []




Detecting C [-std=c11] compiler features compiled with the following output:
Change Dir: /media/bindesh/WORK/00_write/libpng-1.6.28/CMakeFiles/CMakeTmp

Run Build Command:"/home/bindesh/bin/android-sdk/cmake/3.6.3155560/bin/ninja" "cmTC_5d10b"
[1/2] Building C object CMakeFiles/cmTC_5d10b.dir/feature_tests.c.o
[2/2] Linking C executable cmTC_5d10b


    Feature record: C_FEATURE:1c_function_prototypes
    Feature record: C_FEATURE:1c_restrict
    Feature record: C_FEATURE:1c_static_assert
    Feature record: C_FEATURE:1c_variadic_macros


Detecting C [-std=c99] compiler features compiled with the following output:
Change Dir: /media/bindesh/WORK/00_write/libpng-1.6.28/CMakeFiles/CMakeTmp

Run Build Command:"/home/bindesh/bin/android-sdk/cmake/3.6.3155560/bin/ninja" "cmTC_bb98c"
[1/2] Building C object CMakeFiles/cmTC_bb98c.dir/feature_tests.c.o
[2/2] Linking C executable cmTC_bb98c


    Feature record: C_FEATURE:1c_function_prototypes
    Feature record: C_FEATURE:1c_restrict
    Feature record: C_FEATURE:0c_static_assert
    Feature record: C_FEATURE:1c_variadic_macros


Detecting C [-std=c90] compiler features compiled with the following output:
Change Dir: /media/bindesh/WORK/00_write/libpng-1.6.28/CMakeFiles/CMakeTmp

Run Build Command:"/home/bindesh/bin/android-sdk/cmake/3.6.3155560/bin/ninja" "cmTC_f387f"
[1/2] Building C object CMakeFiles/cmTC_f387f.dir/feature_tests.c.o
[2/2] Linking C executable cmTC_f387f


    Feature record: C_FEATURE:1c_function_prototypes
    Feature record: C_FEATURE:0c_restrict
    Feature record: C_FEATURE:0c_static_assert
    Feature record: C_FEATURE:0c_variadic_macros
Performing C SOURCE FILE Test HAVE_LD_VERSION_SCRIPT succeeded with the following output:
Change Dir: /media/bindesh/WORK/00_write/libpng-1.6.28/CMakeFiles/CMakeTmp

Run Build Command:"/home/bindesh/bin/android-sdk/cmake/3.6.3155560/bin/ninja" "cmTC_d0d1b"
[1/2] Building C object CMakeFiles/cmTC_d0d1b.dir/src.c.o
[2/2] Linking C executable cmTC_d0d1b

Source file was:
void sym(void) {}
void sym2(void) {}
int main(void) {return 0;}

Head of CMakeLists.txt file for reference

# CMakeLists.txt

# Copyright (C) 2007,2009-2016 Glenn Randers-Pehrson
# Written by Christian Ehrlicher, 2007
# Revised by Roger Lowman, 2009-2010
# Revised by Clifford Yapp, 2011-2012
# Revised by Roger Leigh, 2016
# Revised by Andreas Franek, 2016

# This code is released under the libpng license.
# For conditions of distribution and use, see the disclaimer
# and license in png.h

cmake_minimum_required(VERSION 2.8.3)
cmake_policy(VERSION 2.8.3)

# Set MacOSX @rpath usage globally.
if (POLICY CMP0020)
  cmake_policy(SET CMP0020 NEW)
endif(POLICY CMP0020)
if (POLICY CMP0042)
  cmake_policy(SET CMP0042 NEW)
endif(POLICY CMP0042)
# Use new variable expansion policy.
if (POLICY CMP0053)
  cmake_policy(SET CMP0053 NEW)
endif(POLICY CMP0053)
if (POLICY CMP0054)
  cmake_policy(SET CMP0054 NEW)
endif(POLICY CMP0054)

set(CMAKE_CONFIGURATION_TYPES "Release;Debug;MinSizeRel;RelWithDebInfo")

project(libpng C)
enable_testing()

set(PNGLIB_MAJOR 1)
set(PNGLIB_MINOR 6)
set(PNGLIB_RELEASE 28)
set(PNGLIB_NAME libpng${PNGLIB_MAJOR}${PNGLIB_MINOR})
set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_RELEASE})


include("/home/bindesh/bin/ndk/build/cmake/android.toolchain.cmake")


# needed packages

#Allow users to specify location of Zlib, 
# Useful if zlib is being built alongside this as a sub-project
option(PNG_BUILD_ZLIB "Custom zlib Location, else find_package is used" OFF) 

This script will build libpng for specified ABI. Change the ABI to build x86, MIPS etc binaries. Sample output binary for above script can be downloaded from here:

 
https://github.com/bindeshkumarsingh/android-native-libs/blob/master/armeabi-v7a_libpng-1.6.28.7z