Android提高之使用NDK把彩图转换灰度图的方法(2)

package com.testToGray; 
public class LibFuns { 
  static { 
    System.loadLibrary("ImgToGray"); 
  } 
  /** 
  * @param width the current view width 
  * @param height the current view height 
  */ 
  public static native int[] ImgToGray(int[] buf, int w, int h); 
}

#include <jni.h> 
#include <stdio.h> 
#include <stdlib.h> 
extern "C" { 
JNIEXPORT jintArray JNICALL Java_com_testToGray_LibFuns_ImgToGray( 
    JNIEnv* env, jobject obj, jintArray buf, int w, int h); 
} 
; 
JNIEXPORT jintArray JNICALL Java_com_testToGray_LibFuns_ImgToGray( 
    JNIEnv* env, jobject obj, jintArray buf, int w, int h) { 
  jint *cbuf; 
  cbuf = env->GetIntArrayElements(buf, false); 
  if (cbuf == NULL) { 
    return 0; /* exception occurred */ 
  } 
  int alpha = 0xFF << 24; 
  for (int i = 0; i < h; i++) { 
    for (int j = 0; j < w; j++) { 
      // 获得像素的颜色 
      int color = cbuf[w * i + j]; 
      int red = ((color & 0x00FF0000) >> 16); 
      int green = ((color & 0x0000FF00) >> 8); 
      int blue = color & 0x000000FF; 
      color = (red + green + blue) / 3; 
      color = alpha | (color << 16) | (color << 8) | color; 
      cbuf[w * i + j] = color; 
    } 
  } 
  int size=w * h; 
  jintArray result = env->NewIntArray(size); 
  env->SetIntArrayRegion(result, 0, size, cbuf); 
  env->ReleaseIntArrayElements(buf, cbuf, 0); 
  return result; 
}

LOCAL_PATH:= $(call my-dir) 
include $(CLEAR_VARS) 
LOCAL_MODULE  := ImgToGray 
LOCAL_SRC_FILES := ImgToGray.cpp 
include $(BUILD_SHARED_LIBRARY)