我终于成功地建立的libjpeg涡轮增压静态库感谢这个 的libjpeg涡轮增压为Android 现在我有一个libjpeg.a和NDK建造产生的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

但我一直没能找到有关下一步该怎么做的任何信息？我是从一个缓冲区（从插座）德codeA JPEG使用生成位图中BitmapFactory其正常工作

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);

我如何使用的libjpeg涡轮增压替代BitmapFactory.de codeByteArray？

how do i replace BitmapFactory.decodeByteArray with libjpeg-turbo?

我的连接code。使用本我的PC上的流

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);

这工作得很好，所以我认为必须有一个Android等价？

which work fine, so i think there must be an android equivalent?

我读到这 https://wiki.linaro.org/BenjaminGaignard/libjpeg-turboAndSkia 这是否意味着使用它是重建的Andr​​oid源，以便它使用的libjpeg涡轮增压的唯一途径？我读的地方有一个兼容的API和本地的API的libjpeg涡轮增压，我很高兴使用任何API是最简单的，因为我不喜欢改造的Andr​​oid

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

我已经尝试了以下内容：  在我的项目的根我创建的文件夹JNI /包括，把turbojpeg.h在那里  在我的项目的根我创建的文件夹JNI / prebuilt并把libjpeg.a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 code，我把

in my java code, i put

private native int tjInitDecompress(); 

在MainActivity 而在我的onCreate添加

in MainActivity and in onCreate i add

int i = tjInitDecompress();
Log.d("MainActivity", "i="+i);

它建立和运行，但崩溃在tjInitDecom preSS

it builds and runs but crashes at tjInitDecompress

在日志中这样说的： 没有找到实现原生LCOM / example.jpegtest / MainActivity; .tjInitDecom preSS（）我

in the log it says: No implementation found for native Lcom/example.jpegtest/MainActivity;.tjInitDecompress ()I

感谢

推荐答案

那么，它是工作的山，但我终于得到了一些工作，所以我不想让任何人谁是有兴趣知道我是怎么做的。

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.

首先我建立了招呼进演示如下描述 https://developer.android.com/tool​​s/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的项目，复制的JNI和改变的C FUNC的名字，以匹配新的包和类名。不使用 - 和_在你的包的名字，或者你会出现问题。只是，x0-9是最好的。

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.

然后我复制所有的libjpeg涡轮增压文件，并显示目录到JNI和测试的NDK建造仍然工作

then i copied all the libjpeg-turbo file and dirs into jni and tested that ndk-build still worked

然后我创建了一个JNI包装的libjpg玩意儿像这样 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);
}

重要的是，你将不得不重新命名com_design2112_fbmslpit_MainActivity你的包和类这个工作

IMPORTANT, you will have to rename com_design2112_fbmslpit_MainActivity to your package and class for this to work

添加tjpegini-arm.c到Android.mk makefile文件，然后运行NDK建造的JNI DIR

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

和的。所以复制到正确的名称和地点

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

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);

    }

这基本上它。可以显示BMP，你想要的任何方式。

that's basically it. you can display the bmp any way you want.

工作的这一点我狗屎负荷找出无JNI NDK的经验都没有。如果有人认为这有用的，发邮件给我一杯啤酒。

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，这里的令人震惊的消息，其采取20ms的脱codeA 450x450的图像。 内置的BitmapFactory.de codeByteArray做它在大约相同的！

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!

如果任何人试图这一点，并得到不同的结果，请记

if anyone else tries this and gets different results, please make a note