Android如何使用libjpeg-turbo库 [英] Android how to use libjpeg-turbo library
问题描述
多亏了这个，我终于设法构建了 libjpeg-turbo 静态库libjpeg-turbo for android现在我有一个 libjpeg.a 和一个由 ndk-build 生成的 libsimd.a
i finally managed to build libjpeg-turbo static library thanks to this libjpeg-turbo for android now i have a libjpeg.a and a libsimd.a generated by ndk-build
但我找不到任何有关下一步做什么的信息?我正在使用 BitmapFactory 中的构建将 jpeg 从缓冲区(从套接字)解码为位图，效果很好
but i have not been able to find any info about what to do next? i'm decode a jpeg from a buffer (from a socket) to a bitmap using the build in BitmapFactory which works fine
byte[] jpgBits = new byte[jpgBitsLen];
dis.readFully(jpgBits);
Bitmap bmp = BitmapFactory.decodeByteArray(jpgBits, 0, jpgBitsLen);
如何用 libjpeg-turbo 替换 BitmapFactory.decodeByteArray?
how do i replace BitmapFactory.decodeByteArray with libjpeg-turbo?
我使用这个在我的电脑上对流进行编码
i encode the stream on my PC using this
tjhandle rmfdJpegCompressor = tjInitCompress();
tjCompress2(rmfdJpegCompressor, (unsigned char *)s_rmfdPixels, MFD_WH, 0, MFD_WH, TJPF_BGRX,
&rmfdBits, &rmfdBitsLen, TJSAMP_420, RMFD_JPEG_QUALITY,
0);
tjDestroy(rmfdJpegCompressor);
哪个工作正常，所以我认为必须有一个 android 等价物?
which work fine, so i think there must be an android equivalent?
我读过这个https://wiki.linaro.org/BenjaminGaignard/libjpeg-turboAndSkia这是否意味着使用它的唯一方法是重建 android 源代码以便它使用 libjpeg-turbo?我在某处读到了 libjpeg-turbo 的兼容性 api 和本机 api，我很乐意使用任何最简单的 api，因为我不喜欢重建 android
i read this https://wiki.linaro.org/BenjaminGaignard/libjpeg-turboAndSkia does this mean the only way to use it is to rebuild android sources so it uses libjpeg-turbo? i read somewhere there is a compatibility api and a native api for libjpeg-turbo and i'm happy to use whatever api is easiest since i don't fancy rebuilding android
我尝试了以下方法:在我的项目根目录下，我创建了文件夹 jni/include 并将 turbojpeg.h 放在那里在我的项目根目录下，我创建了文件夹 jni/prebuilt 并将 libjpeg.a 放在那里
i've tried the following: under my project root i created folders jni/include and put turbojpeg.h in there under my project root i created folders jni/prebuilt and put libjpeg.a in there
在我的java代码中，我放了
in my java code, i put
private native int tjInitDecompress();
在 MainActivity并在 onCreate 我添加
in MainActivity and in onCreate i add
int i = tjInitDecompress();
Log.d("MainActivity", "i="+i);
它构建并运行，但在 tjInitDecompress 时崩溃
it builds and runs but crashes at tjInitDecompress
在日志中它说:未找到本机 Lcom/example.jpegtest/MainActivity;.tjInitDecompress ()I
in the log it says: No implementation found for native Lcom/example.jpegtest/MainActivity;.tjInitDecompress ()I
谢谢
推荐答案
嗯，工作量很大，但我终于找到了一些工作，所以我想让任何有兴趣的人知道我是如何做到的.
well, its been a mountain of work but i finally got something working so i want to let anyone who's interested know how i did it.
首先我按照这里的描述构建了 hello-jin 演示https://developer.android.com/tools/sdk/ndk/index.html
first i built the hello-jin demo as described here https://developer.android.com/tools/sdk/ndk/index.html
然后我创建了一个新项目，复制了 jni 并更改了 c func 的名称以匹配新的包和类名.不要在你的包名中使用 - 和 _ 否则你会遇到问题.最好只有 a-x0-9.
then i created a new project, copied the jni and changed the names of the c func to match the new package and class name. don't use - and _ in your package name or you will have problems. just a-x0-9 is best.
然后我将所有 libjpeg-turbo 文件和目录复制到 jni 并测试 ndk-build 仍然有效
then i copied all the libjpeg-turbo file and dirs into jni and tested that ndk-build still worked
然后我为这样的 libjpg funs 创建了一个 jni 包装器tjpegini-arm.c
then i created a jni wrapper for the libjpg funs like this tjpegini-arm.c
/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include <jni.h>
#include "turbojpeg.h"
/*
* Class: libjpegturbo_jniapi
* Method: tjInitDecompress
* Signature: ()I
*/
//package com.design2112.fbmslpit
//public class MainActivity
jint JNICALL Java_com_design2112_fbmslpit_MainActivity_tjInitDecompress
(JNIEnv *env, jobject thisObj)
{
return (int)tjInitDecompress();
}
/*
* Class: libjpegturbo_jniapi
* Method: tjDecompressHeader2
* Signature: (I[BI)I
*/
jint JNICALL Java_com_design2112_fbmslpit_MainActivity_tjDecompressHeader2
(JNIEnv *env, jobject thisObj, jint handle, jbyteArray jpegBuf, jint jpegSize)
{
jbyte *real_jpegBuf = (*env)->GetByteArrayElements(env, jpegBuf, 0);
if (!real_jpegBuf) return -1;
//jsize length = (*env)->GetArrayLength(env, real_jpegBuf);
/*for (i = 0; i < length; i++) {
sum += inCArray[i];
}*/
int width, height, jpegSubsamp;
int ret = tjDecompressHeader2((tjhandle)handle,
(unsigned char *)real_jpegBuf, (unsigned long)jpegSize, &width, &height,
&jpegSubsamp);
if(ret!=0) {
return 0;
}
// ok, so pack width and height together
return width<<16 | height;
}
/*
* Class: libjpegturbo_jniapi
* Method: tjDecompress2
* Signature: (I[BI[IIIIII)V
*/
void JNICALL Java_com_design2112_fbmslpit_MainActivity_tjDecompress2
(JNIEnv *env, jobject thisObj, jint handle, jbyteArray jpegBuf, jint jpegSize, jintArray dstBuf,
jint width, jint pitch, jint height, jint pixelFormat, jint flags)
{
jbyte *real_jpegBuf = (*env)->GetByteArrayElements(env, jpegBuf, 0);
if (!real_jpegBuf) return;
jint *real_dstBuf = (*env)->GetIntArrayElements(env, dstBuf, 0);
if (!real_dstBuf) return;
jsize length = (*env)->GetArrayLength(env, jpegBuf);
tjDecompress2((tjhandle)handle,
(unsigned char *)real_jpegBuf, (unsigned long)jpegSize, (unsigned char *)real_dstBuf,
width, pitch, height, pixelFormat, flags);
}
/*
* Class: libjpegturbo_jniapi
* Method: tjDestroy
* Signature: (I)V
*/
void JNICALL Java_com_design2112_fbmslpit_MainActivity_tjDestroy
(JNIEnv *env, jobject thisObj, jint handle)
{
tjDestroy((tjhandle)handle);
}
重要提示，您必须将 com_design2112_fbmslpit_MainActivity 重命名为您的包和类才能正常工作
IMPORTANT, you will have to rename com_design2112_fbmslpit_MainActivity to your package and class for this to work
将 tjpegini-arm.c 添加到 Android.mk makefile 然后在 jni 目录中运行 ndk-build
add tjpegini-arm.c to the Android.mk makefile then run ndk-build in the jni dir
ndk-build NDK_PROJECT_PATH=. APP_BUILD_SCRIPT=./Android.mk obj/local/armeabi/libjpeg.so LOCAL_ARM_MODE=arm
并将 .so 复制到正确的名称和位置
and copy the .so to the right name and place
cp obj/local/armeabi/libjpeg.so ../libs/armeabi/libtjpegjni-arm.so
然后在我的 MainAvtivity.java 中
then in my MainAvtivity.java
public class MainActivity extends Activity {
public native int tjInitDecompress();
public native int tjDecompressHeader2(int handle, byte[] jpegBits, int jpegBitsLen);
public native void tjDecompress2(int handle, byte[] jpegBits,
int jpegBitsLen, int[] outbuffer, int width, int pitch, int height,
int pixelFormat, int flags);
public native void tjDestroy(int handle);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
File sdcard = Environment.getExternalStorageDirectory();
//Get the text file
File file = new File(sdcard,"/Download/test.jpg");
int jpegBitsLen = (int) file.length();
byte[] jpegBits = new byte[jpegBitsLen];
DataInputStream dis;
try {
dis = new DataInputStream(new FileInputStream(file));
dis.readFully(jpegBits);
dis.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.loadLibrary("tjpegjni-arm");
int jpegDec = tjInitDecompress();
int wh = tjDecompressHeader2(jpegDec, jpegBits, jpegBitsLen);
int width = wh>>16;
int height = wh&0x7fff;
int[] buffer = new int[width*height];
tjDecompress2(jpegDec, jpegBits, jpegBitsLen, buffer, width, 0/*pitch*/, height, 2 /*TJPF_RGBX*/, 0);
tjDestroy(jpegDec);
Bitmap bmp = Bitmap.createBitmap(buffer, width, height, Bitmap.Config.ARGB_8888);
}
基本上就是这样.你可以以任何你想要的方式显示bmp.
that's basically it. you can display the bmp any way you want.
这对我来说也是一大堆工作，以弄清楚根本没有 jni ndk 经验.如果有人觉得这很有用，请给我发电子邮件.
this too me a shit load of work to figure out having no jni ndk experience at all. if someone finds this usefull, email me a beer.
更新，这是一个令人震惊的消息，解码 450x450 图像需要 20 毫秒.内置的 BitmapFactory.decodeByteArray 也差不多！
UPDATE, here's the shocking news, its taking 20ms to decode a 450x450 image. the built in BitmapFactory.decodeByteArray does it in about the same!
如果其他人尝试此操作并得到不同的结果，请记下
if anyone else tries this and gets different results, please make a note
这篇关于Android如何使用libjpeg-turbo库的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
