如何使用JNI位图操作帮助使用大图像时避免OOM？ [关闭]

问题描述 投票：45回答：1

背景

大部分的时间，Android变得OOM是由于使用过多位图和/或创建大的位图。

最近，我决定尝试JNI，以允许通过存储在JNI侧数据本身避免OOM。

用JNI乱搞了一段时间后，我已经创建了SO寻求帮助和分享我的知识一些帖子，现在我已经决定要与您分享一些更多的代码。这里是万一有人有兴趣阅读的研究结果或有助于帖子：

这个时候，我已经添加到存储，恢复，剪切，旋转位图的能力。它应该是很容易添加更多的选择，我会很高兴，如果这里的其他人将自己的代码添加到更多有用的功能。

这样的代码我是要告诉实际上是合并所有我所创建的东西。

使用的示例代码：

Bitmap bitmap=BitmapFactory.decodeResource(getResources(),R.drawable.ic_launcher);
final int width=bitmap.getWidth(),height=bitmap.getHeight();
// store the bitmap in the JNI "world"
final JniBitmapHolder bitmapHolder=new JniBitmapHolder(bitmap);
// no need for the bitmap on the java "world", since the operations are done on the JNI "world"
bitmap.recycle();
// crop a center square from the bitmap, from (0.25,0.25) to (0.75,0.75) of the bitmap.
bitmapHolder.cropBitmap(width/4,height/4,width*3/4,height*3/4);
//rotate the bitmap:
bitmapHolder.rotateBitmapCcw90();
//get the output java bitmap , and free the one on the JNI "world"
bitmap=bitmapHolder.getBitmapAndFree();

该项目可在github

  • 项目页面，请在github here。
  • 随时给建议和贡献。

重要笔记

如图所示here，再加上同调：

  • 在此处写入电流特性（更多更新的项目页面上）： 商店 恢复 旋转90度逆时针 作物。
  • 我已经采取了这种代码的办法是两个内存效率（只使用，我需要的内存，并释放它不需要时），和CPU效率（我试图尽可能使用指针和CPU内存优化）。
  • 为了获得最佳性能，我所做甚少验证，尤其是在JNI部分。它可能是最好的管理上的Java“世界”的验证。
  • 仍然有很多，我认为应该加入缺少的功能，我希望我将不得不增加他们的时间。如果有人愿意出力，我会很高兴，他们添加代码了。这里是我想可能是有用的功能： 获得当前的位图信息 扩展位图，其中包括要使用的算法选择（最近邻居和双线性插值应该是足够了）。 使用不同的位图格式 做解码内JNI，避免了Java的位图的创建（而不是使用堆在Java世界），从一开始，只是在最后，当你所有的操作完成。 人脸检测 在任意角度旋转，或者至少明显的。目前我只加90度计数时钟的转动明智的。
android bitmap android-ndk java-native-interface out-of-memory
1个回答
22
投票

注：这是一个有点老的代码。在最新的一个，检查出github项目页面。

JNI / Android.mk

LOCAL_PATH := $(call my-dir)

#bitmap operations module
include $(CLEAR_VARS)

LOCAL_MODULE    := JniBitmapOperations
LOCAL_SRC_FILES := JniBitmapOperations.cpp
LOCAL_LDLIBS := -llog
LOCAL_LDFLAGS += -ljnigraphics

include $(BUILD_SHARED_LIBRARY)
APP_OPTIM := debug
LOCAL_CFLAGS := -g

#if you need to add more module, do the same as the one we started with (the one with the CLEAR_VARS)

范围/ Jnibitmapoprashanskkpp

#include <jni.h>
#include <jni.h>
#include <android/log.h>
#include <stdio.h>
#include <android/bitmap.h>
#include <cstring>
#include <unistd.h>

#define  LOG_TAG    "DEBUG"
#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

extern "C"
  {
  JNIEXPORT jobject JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniStoreBitmapData(JNIEnv * env, jobject obj, jobject bitmap);
  JNIEXPORT jobject JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniGetBitmapFromStoredBitmapData(JNIEnv * env, jobject obj, jobject handle);
  JNIEXPORT void JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniFreeBitmapData(JNIEnv * env, jobject obj, jobject handle);
  JNIEXPORT void JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniRotateBitmapCcw90(JNIEnv * env, jobject obj, jobject handle);
  JNIEXPORT void JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniCropBitmap(JNIEnv * env, jobject obj, jobject handle, uint32_t left, uint32_t top, uint32_t right, uint32_t bottom);
  }

class JniBitmap
  {
  public:
    uint32_t* _storedBitmapPixels;
    AndroidBitmapInfo _bitmapInfo;
    JniBitmap()
      {
      _storedBitmapPixels = NULL;
      }
  };

/**crops the bitmap within to be smaller. note that no validations are done*/ //
JNIEXPORT void JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniCropBitmap(JNIEnv * env, jobject obj, jobject handle, uint32_t left, uint32_t top, uint32_t right, uint32_t bottom)
  {
  JniBitmap* jniBitmap = (JniBitmap*) env->GetDirectBufferAddress(handle);
  if (jniBitmap->_storedBitmapPixels == NULL)
    return;
  uint32_t* previousData = jniBitmap->_storedBitmapPixels;
  uint32_t oldWidth = jniBitmap->_bitmapInfo.width;
  uint32_t newWidth = right - left, newHeight = bottom - top;
  uint32_t* newBitmapPixels = new uint32_t[newWidth * newHeight];
  uint32_t* whereToGet = previousData + left + top * oldWidth;
  uint32_t* whereToPut = newBitmapPixels;
  for (int y = top; y < bottom; ++y)
    {
    memcpy(whereToPut, whereToGet, sizeof(uint32_t) * newWidth);
    whereToGet += oldWidth;
    whereToPut += newWidth;
    }
  //done copying , so replace old data with new one
  delete[] previousData;
  jniBitmap->_storedBitmapPixels = newBitmapPixels;
  jniBitmap->_bitmapInfo.width = newWidth;
  jniBitmap->_bitmapInfo.height = newHeight;
  }

/**rotates the inner bitmap data by 90 degress counter clock wise*/ //
JNIEXPORT void JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniRotateBitmapCcw90(JNIEnv * env, jobject obj, jobject handle)
  {
  JniBitmap* jniBitmap = (JniBitmap*) env->GetDirectBufferAddress(handle);
  if (jniBitmap->_storedBitmapPixels == NULL)
    return;
  uint32_t* previousData = jniBitmap->_storedBitmapPixels;
  AndroidBitmapInfo bitmapInfo = jniBitmap->_bitmapInfo;
  uint32_t* newBitmapPixels = new uint32_t[bitmapInfo.height * bitmapInfo.width];
  int whereToPut = 0;
  // A.D D.C
  // ...>...
  // B.C A.B
  for (int x = bitmapInfo.width - 1; x >= 0; --x)
    for (int y = 0; y < bitmapInfo.height; ++y)
      {
      uint32_t pixel = previousData[bitmapInfo.width * y + x];
      newBitmapPixels[whereToPut++] = pixel;
      }
  delete[] previousData;
  jniBitmap->_storedBitmapPixels = newBitmapPixels;
  uint32_t temp = bitmapInfo.width;
  bitmapInfo.width = bitmapInfo.height;
  bitmapInfo.height = temp;
  }

/**free bitmap*/  //
JNIEXPORT void JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniFreeBitmapData(JNIEnv * env, jobject obj, jobject handle)
  {
  JniBitmap* jniBitmap = (JniBitmap*) env->GetDirectBufferAddress(handle);
  if (jniBitmap->_storedBitmapPixels == NULL)
    return;
  delete[] jniBitmap->_storedBitmapPixels;
  jniBitmap->_storedBitmapPixels = NULL;
  delete jniBitmap;
  }

/**restore java bitmap (from JNI data)*/  //
JNIEXPORT jobject JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniGetBitmapFromStoredBitmapData(JNIEnv * env, jobject obj, jobject handle)
  {
  JniBitmap* jniBitmap = (JniBitmap*) env->GetDirectBufferAddress(handle);
  if (jniBitmap->_storedBitmapPixels == NULL)
    {
    LOGD("no bitmap data was stored. returning null...");
    return NULL;
    }
  //
  //creating a new bitmap to put the pixels into it - using Bitmap Bitmap.createBitmap (int width, int height, Bitmap.Config config) :
  //
  //LOGD("creating new bitmap...");
  jclass bitmapCls = env->FindClass("android/graphics/Bitmap");
  jmethodID createBitmapFunction = env->GetStaticMethodID(bitmapCls, "createBitmap", "(IILandroid/graphics/Bitmap$Config;)Landroid/graphics/Bitmap;");
  jstring configName = env->NewStringUTF("ARGB_8888");
  jclass bitmapConfigClass = env->FindClass("android/graphics/Bitmap$Config");
  jmethodID valueOfBitmapConfigFunction = env->GetStaticMethodID(bitmapConfigClass, "valueOf", "(Ljava/lang/String;)Landroid/graphics/Bitmap$Config;");
  jobject bitmapConfig = env->CallStaticObjectMethod(bitmapConfigClass, valueOfBitmapConfigFunction, configName);
  jobject newBitmap = env->CallStaticObjectMethod(bitmapCls, createBitmapFunction, jniBitmap->_bitmapInfo.width, jniBitmap->_bitmapInfo.height, bitmapConfig);
  //
  // putting the pixels into the new bitmap:
  //
  int ret;
  void* bitmapPixels;
  if ((ret = AndroidBitmap_lockPixels(env, newBitmap, &bitmapPixels)) < 0)
    {
    LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
    return NULL;
    }
  uint32_t* newBitmapPixels = (uint32_t*) bitmapPixels;
  int pixelsCount = jniBitmap->_bitmapInfo.height * jniBitmap->_bitmapInfo.width;
  memcpy(newBitmapPixels, jniBitmap->_storedBitmapPixels, sizeof(uint32_t) * pixelsCount);
  AndroidBitmap_unlockPixels(env, newBitmap);
  //LOGD("returning the new bitmap");
  return newBitmap;
  }

/**store java bitmap as JNI data*/  //
JNIEXPORT jobject JNICALL Java_com_jni_bitmap_1operations_JniBitmapHolder_jniStoreBitmapData(JNIEnv * env, jobject obj, jobject bitmap)
  {
  AndroidBitmapInfo bitmapInfo;
  uint32_t* storedBitmapPixels = NULL;
  //LOGD("reading bitmap info...");
  int ret;
  if ((ret = AndroidBitmap_getInfo(env, bitmap, &bitmapInfo)) < 0)
    {
    LOGE("AndroidBitmap_getInfo() failed ! error=%d", ret);
    return NULL;
    }
  LOGD("width:%d height:%d stride:%d", bitmapInfo.width, bitmapInfo.height, bitmapInfo.stride);
  if (bitmapInfo.format != ANDROID_BITMAP_FORMAT_RGBA_8888)
    {
    LOGE("Bitmap format is not RGBA_8888!");
    return NULL;
    }
  //
  //read pixels of bitmap into native memory :
  //
  //LOGD("reading bitmap pixels...");
  void* bitmapPixels;
  if ((ret = AndroidBitmap_lockPixels(env, bitmap, &bitmapPixels)) < 0)
    {
    LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
    return NULL;
    }
  uint32_t* src = (uint32_t*) bitmapPixels;
  storedBitmapPixels = new uint32_t[bitmapInfo.height * bitmapInfo.width];
  int pixelsCount = bitmapInfo.height * bitmapInfo.width;
  memcpy(storedBitmapPixels, src, sizeof(uint32_t) * pixelsCount);
  AndroidBitmap_unlockPixels(env, bitmap);
  JniBitmap *jniBitmap = new JniBitmap();
  jniBitmap->_bitmapInfo = bitmapInfo;
  jniBitmap->_storedBitmapPixels = storedBitmapPixels;
  return env->NewDirectByteBuffer(jniBitmap, 0);
  }

SRC / COM / JNI / bitmap_operations / JniBitmapHolder.java

package com.jni.bitmap_operations;
import java.nio.ByteBuffer;
import android.graphics.Bitmap;
import android.util.Log;

public class JniBitmapHolder
  {
  ByteBuffer _handler =null;
  static
    {
    System.loadLibrary("JniBitmapOperations");
    }

  private native ByteBuffer jniStoreBitmapData(Bitmap bitmap);

  private native Bitmap jniGetBitmapFromStoredBitmapData(ByteBuffer handler);

  private native void jniFreeBitmapData(ByteBuffer handler);

  private native void jniRotateBitmapCcw90(ByteBuffer handler);

  private native void jniCropBitmap(ByteBuffer handler,final int left,final int top,final int right,final int bottom);

  public JniBitmapHolder()
    {}

  public JniBitmapHolder(final Bitmap bitmap)
    {
    storeBitmap(bitmap);
    }

  public void storeBitmap(final Bitmap bitmap)
    {
    if(_handler!=null)
      freeBitmap();
    _handler=jniStoreBitmapData(bitmap);
    }

  public void rotateBitmapCcw90()
    {
    if(_handler==null)
      return;
    jniRotateBitmapCcw90(_handler);
    }

  public void cropBitmap(final int left,final int top,final int right,final int bottom)
    {
    if(_handler==null)
      return;
    jniCropBitmap(_handler,left,top,right,bottom);
    }

  public Bitmap getBitmap()
    {
    if(_handler==null)
      return null;
    return jniGetBitmapFromStoredBitmapData(_handler);
    }

  public Bitmap getBitmapAndFree()
    {
    final Bitmap bitmap=getBitmap();
    freeBitmap();
    return bitmap;
    }

  public void freeBitmap()
    {
    if(_handler==null)
      return;
    jniFreeBitmapData(_handler);
    _handler=null;
    }

  @Override
  protected void finalize() throws Throwable
    {
    super.finalize();
    if(_handler==null)
      return;
    Log.w("DEBUG","JNI bitmap wasn't freed nicely.please rememeber to free the bitmap as soon as you can");
    freeBitmap();
    }
  }
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