Android JNI处理图片实现黑白滤镜的方法

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
       native-lib

       # Sets the library as a shared library.
       SHARED

       # Provides a relative path to your source file(s).
       src/main/cpp/native-lib.cpp )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
       log-lib

       # Specifies the name of the NDK library that
       # you want CMake to locate.
       log )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
            native-lib jnigraphics

            # Links the target library to the log library
            # included in the NDK.
            ${log-lib} )

public class MainActivity extends AppCompatActivity {

  private ImageView mImg1, mImg2;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mImg1 = (ImageView) findViewById(R.id.img_test1_id);
    mImg2 = (ImageView) findViewById(R.id.img_test2_id);
  }


  /**
   * 确定native处理图片的接口
   * @param bitmap 需要被处理的图片
   */
  public native void nativeProcessBitmap(Bitmap bitmap);

  /**
   * 引入native库
   */
  static {
    System.loadLibrary("native-lib");
  }

  /**
   * 点击开始加载图片
   * @param view
   */
  public void onLoadClick(View view) {
    Bitmap originalBitmap = loadBitmap();
    mImg1.setImageBitmap(originalBitmap);
    Bitmap resultBitmap = processBitmap(originalBitmap);
    mImg2.setImageBitmap(resultBitmap);
  }

  /**
   * 从assets中加载图片
   * @return
   */
  private Bitmap loadBitmap() {
    Bitmap bmp = null;
    AssetManager am = getResources().getAssets();
    try {
      InputStream is = am.open("test_img.jpg");
      BitmapFactory.Options options = new BitmapFactory.Options();
      bmp = BitmapFactory.decodeStream(is ,null , options);
      is.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
    return bmp;
  }

  /**
   * 处理图片，此方法中会调用nativeProcessBitmap
   * @param bitmap
   * @return
   */
  private Bitmap processBitmap(Bitmap bitmap) {
    Bitmap bmp = bitmap.copy(Bitmap.Config.ARGB_8888, true);
    nativeProcessBitmap( bmp);
    return bmp;
  }
}

#include <jni.h>
#include <string>

#include <android/bitmap.h>
#include <android/log.h>

#ifndef eprintf
#define eprintf(...) __android_log_print(ANDROID_LOG_ERROR,"@",__VA_ARGS__)

#endif

#define MAKE_RGB565(r,g,b) ((((r) >> 3) << 11) | (((g) >> 2) << 5) | ((b) >> 3))
#define MAKE_ARGB(a,r,g,b) ((a&0xff)<<24) | ((r&0xff)<<16) | ((g&0xff)<<8) | (b&0xff)

#define RGB565_R(p) ((((p) & 0xF800) >> 11) << 3)
#define RGB565_G(p) ((((p) & 0x7E0 ) >> 5) << 2)
#define RGB565_B(p) ( ((p) & 0x1F )    << 3)

#define RGB8888_A(p) (p & (0xff<<24) >> 24 )
#define RGB8888_R(p) (p & (0xff<<16) >> 16 )
#define RGB8888_G(p) (p & (0xff<<8) >> 8 )
#define RGB8888_B(p) (p & (0xff) )

extern "C"
{

  JNIEXPORT void JNICALL
  Java_com_live_longsiyang_jnibitmapdemo_MainActivity_nativeProcessBitmap(JNIEnv *env,
                                      jobject instance,
                                      jobject bitmap) {

    if (bitmap == NULL) {
      eprintf("bitmap is null\n");
      return;
    }

    AndroidBitmapInfo bitmapInfo;
    memset(&bitmapInfo , 0 , sizeof(bitmapInfo));
    // Need add "jnigraphics" into target_link_libraries in CMakeLists.txt
    AndroidBitmap_getInfo(env , bitmap , &bitmapInfo);

    // Lock the bitmap to get the buffer
    void * pixels = NULL;
    int res = AndroidBitmap_lockPixels(env, bitmap, &pixels);

    // From top to bottom
    int x = 0, y = 0;
    for (y = 0; y < bitmapInfo.height; ++y) {
      // From left to right
      for (x = 0; x < bitmapInfo.width; ++x) {
        int a = 0, r = 0, g = 0, b = 0;
        void *pixel = NULL;
        // Get each pixel by format

        if(bitmapInfo.format == ANDROID_BITMAP_FORMAT_RGBA_8888)
        {
          pixel = ((uint32_t *)pixels) + y * bitmapInfo.width + x;
          int r,g,b;
          uint32_t v = *((uint32_t *)pixel);
          r = RGB8888_R(v);
          g = RGB8888_G(v);
          b = RGB8888_B(v);
          int sum = r+g+b;
          *((uint32_t *)pixel) = MAKE_ARGB(0x1f , sum/3, sum/3, sum/3);
        }
        else if (bitmapInfo.format == ANDROID_BITMAP_FORMAT_RGB_565) {
          pixel = ((uint16_t *)pixels) + y * bitmapInfo.width + x;
          int r,g,b;
          uint16_t v = *((uint16_t *)pixel);
          r = RGB565_R(v);
          g = RGB565_G(v);
          b = RGB565_B(v);
          int sum = r+g+b;
          *((uint16_t *)pixel) = MAKE_RGB565(sum/3, sum/3, sum/3); }
      }
    }

    AndroidBitmap_unlockPixels(env, bitmap);

  }

}

    AndroidBitmapInfo bitmapInfo;
    memset(&bitmapInfo , 0 , sizeof(bitmapInfo));
    // Need add "jnigraphics" into target_link_libraries in CMakeLists.txt
    AndroidBitmap_getInfo(env , bitmap , &bitmapInfo);

void * pixels = NULL;
int res = AndroidBitmap_lockPixels(env, bitmap, &pixels);

AndroidBitmap_unlockPixels(env, bitmap);