最近的學習真的比較困難,因為學習了SDK開發項目後,做了一些簡單的項目後,覺得在UI線程中加載較多圖片時,總會出現卡頓的感覺,特別是手指滑動下拉時,這種卡頓更易察覺到,而java的結構化開發能力確實是很強大的,使用java開發確實是一件非常享受的事情,但是java在一些高密度的計算中是沒有什麼優勢的,在享受內存自動回收時也會遇到一些不如意的事。任何語言或事物,總會有優缺點,這是java如此簡單易用的一個副作用。所以為了不使java的副作用危害到開發者使用java,java產生了一種非常有吸引力的的技術JNI技術,這種技術可以讓Java調用C/C++和其他的語言所寫的程序。而這種技術也在android中得以支持--NDK, NDK提供了一系列的工具，幫助開發者快速開發C（或C++）的動態庫，並能自動將so和java應用一起打包成apk,使用起來非常方便。
說了一堆的廢話,接下來記錄下自己最近所學習到的東西,可以說NDK重要的學習資料之一就是android的官方網站提供的資料,包括下載了NDK後,也能看到一些簡單的使用了NDK的項目源碼,這些源碼能讓我們知道android官方建議我們如何使用NDK,甚至可以用純C/C++語言開發應用,但這並不是我感興趣的,具體原因就不說了。
按照官方的使用方式還是比較簡單的,這裡寫了一個用C語言提取照片灰度圖的函數,並在java中調用
先寫java代碼
public class PhotoProcessingActivity extends Activity{
private Bitmap bmOriginal,bmGray;
private ImageView iv;
private Button btGray,btOpen;
static{
System.loadLibrary("PhotoProcessing");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.photo_processing_activity);
setup();
}
public void setup(){
iv = (ImageView) findViewById(R.id.showPhoto);
bmOriginal = ImageShare.mBitmap;
iv.setImageBitmap(bmOriginal);
btGray = (Button) findViewById(R.id.btGray);
btGray.setOnClickListener(onclick);
btOpen = (Button) findViewById(R.id.btOpen);
btOpen.setOnClickListener(onclick);
}
OnClickListener onclick = new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch(v.getId()){
case R.id.btGray:
bmGray = Bitmap.createBitmap(bmOriginal.getWidth(), bmOriginal.getHeight(), Config.ALPHA_8);
grayPhoto(bmOriginal, bmGray);
iv.setImageBitmap(bmGray);
break;
case R.id.btOpen:
Intent intent = new Intent(PhotoProcessingActivity.this,
SurfaceProcessingActivity.class);
startActivity(intent);
break;
}
}
};
public native void grayPhoto(Bitmap bmOriginal,Bitmap bmGray);
}使用javah工具得到頭文件PhotoProcessingActivity.h並且添加處理圖片所需的一些頭文件,這些頭文件都是NDK中的include中自帶的,使用時可以把把該文件夾鏈接進去
/* DO NOT EDIT THIS FILE - it is machine generated */ #include接著編寫C代碼/* Header for class com_example_photoprocessing_activity_PhotoProcessingActivity */ #include #include #include #include #ifndef _Included_com_example_photoprocessing_activity_PhotoProcessingActivity #define _Included_com_example_photoprocessing_activity_PhotoProcessingActivity #ifdef __cplusplus extern "C" { #endif #undef com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_PRIVATE #define com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_PRIVATE 0L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_WORLD_READABLE #define com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_WORLD_READABLE 1L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_WORLD_WRITEABLE #define com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_WORLD_WRITEABLE 2L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_APPEND #define com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_APPEND 32768L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_MULTI_PROCESS #define com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_MULTI_PROCESS 4L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING #define com_example_photoprocessing_activity_PhotoProcessingActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING 8L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_AUTO_CREATE #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_AUTO_CREATE 1L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_DEBUG_UNBIND #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_DEBUG_UNBIND 2L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_NOT_FOREGROUND #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_NOT_FOREGROUND 4L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_ABOVE_CLIENT #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_ABOVE_CLIENT 8L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_ALLOW_OOM_MANAGEMENT #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_ALLOW_OOM_MANAGEMENT 16L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_WAIVE_PRIORITY #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_WAIVE_PRIORITY 32L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_IMPORTANT #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_IMPORTANT 64L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_ADJUST_WITH_ACTIVITY #define com_example_photoprocessing_activity_PhotoProcessingActivity_BIND_ADJUST_WITH_ACTIVITY 128L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_CONTEXT_INCLUDE_CODE #define com_example_photoprocessing_activity_PhotoProcessingActivity_CONTEXT_INCLUDE_CODE 1L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_CONTEXT_IGNORE_SECURITY #define com_example_photoprocessing_activity_PhotoProcessingActivity_CONTEXT_IGNORE_SECURITY 2L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_CONTEXT_RESTRICTED #define com_example_photoprocessing_activity_PhotoProcessingActivity_CONTEXT_RESTRICTED 4L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_RESULT_CANCELED #define com_example_photoprocessing_activity_PhotoProcessingActivity_RESULT_CANCELED 0L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_RESULT_OK #define com_example_photoprocessing_activity_PhotoProcessingActivity_RESULT_OK -1L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_RESULT_FIRST_USER #define com_example_photoprocessing_activity_PhotoProcessingActivity_RESULT_FIRST_USER 1L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_DISABLE #define com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_DISABLE 0L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_DIALER #define com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_DIALER 1L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_SHORTCUT #define com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_SHORTCUT 2L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_SEARCH_LOCAL #define com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L #undef com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_SEARCH_GLOBAL #define com_example_photoprocessing_activity_PhotoProcessingActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L /* * Class: com_example_photoprocessing_activity_PhotoProcessingActivity * Method: grayPhoto * Signature: (Landroid/graphics/Bitmap;Landroid/graphics/Bitmap;)V */ /** * xuan */ #define LOG_TAG "PhotoProcessing" #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__) #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__) typedef struct { uint8_t alpha; uint8_t red; uint8_t green; uint8_t blue; } argb; JNIEXPORT void JNICALL Java_com_example_photoprocessing_activity_PhotoProcessingActivity_grayPhoto (JNIEnv *, jobject, jobject, jobject); #ifdef __cplusplus } #endif #endif
#include "PhotoProcessingActivity.h"
JNIEXPORT void JNICALL Java_com_example_photoprocessing_activity_PhotoProcessingActivity_grayPhoto(
JNIEnv *env, jobject photoProcessingActivity, jobject bmOriginal,
jobject bmGray) {
AndroidBitmapInfo origanalColor;
void* pixelscolor;
AndroidBitmapInfo infogray;
void* pixelsgray;
int ret;
int y;
int x;
LOGI("In convertToGray");
if ((ret = AndroidBitmap_getInfo(env, bmOriginal, &origanalColor)) < 0) {
LOGE("AndroidBitmap_getInfo() failed ! error=%d", ret);
return;
}
if ((ret = AndroidBitmap_getInfo(env, bmGray, &infogray)) < 0) {
LOGE("AndroidBitmap_getInfo() failed ! error=%d", ret);
return;
}
LOGI(
"original image :: width is %d; height is %d; stride is %d; format is %d;flags is %d,stride is %u", origanalColor.width, origanalColor.height, origanalColor.stride, origanalColor.format, origanalColor.flags, origanalColor.stride);
if (origanalColor.format != ANDROID_BITMAP_FORMAT_RGBA_8888) {
LOGE("Bitmap format is not RGBA_8888 !");
//return;
}
if (origanalColor.format == ANDROID_BITMAP_FORMAT_RGB_565) {
LOGI("Original Image is ANDROID_BITMAP_FORMAT_RGB_565");
if ((ret = AndroidBitmap_lockPixels(env, bmOriginal, &pixelscolor))
< 0) {
LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
}
if ((ret = AndroidBitmap_lockPixels(env, bmGray, &pixelsgray)) < 0) {
LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
}
// modify pixels with image processing algorithm
for (y = 0; y < origanalColor.height; y++) {
__uint16_t * line = (__uint16_t *) pixelscolor;
uint8_t * grayline = (uint8_t *) pixelsgray;
for (x = 0; x < origanalColor.width; x++) {
grayline[x] = (uint8_t)(((line[x] >> 11 <<3) + (line[x] >> 5 & 63 * 16) + (line[x]&31 * 8)) / 3);
//LOGI("%d %d %d %d",line[x].alpha,line[x].red,line[x].green,line[x].blue);
/*if(x ==0){
LOGI("line:%o grayline %o ",line[x],grayline[x]);
}*/
}
pixelscolor = (char *) pixelscolor + origanalColor.stride;
pixelsgray = (char *) pixelsgray + infogray.stride;
}
LOGI("unlocking pixels");
AndroidBitmap_unlockPixels(env, bmOriginal);
AndroidBitmap_unlockPixels(env, bmGray);
LOGI("Return !! ");
return ;
}
LOGI(
"gray image :: width is %d; height is %d; stride is %d; format is %d;flags is %d %d,stride is %u", infogray.width, infogray.height, infogray.stride, infogray.format, infogray.flags, infogray.stride);
if (infogray.format != ANDROID_BITMAP_FORMAT_A_8) {
LOGE("Bitmap format is not A_8 !");
return;
}
if ((ret = AndroidBitmap_lockPixels(env, bmOriginal, &pixelscolor)) < 0) {
LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
}
if ((ret = AndroidBitmap_lockPixels(env, bmGray, &pixelsgray)) < 0) {
LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
}
// modify pixels with image processing algorithm
for (y = 0; y < origanalColor.height; y++) {
argb * line = (argb *) pixelscolor;
uint8_t * grayline = (uint8_t *) pixelsgray;
for (x = 0; x < origanalColor.width; x++) {
grayline[x] = (line[x].red + line[x].green + line[x].blue) / 3;
}
pixelscolor = (char *) pixelscolor + origanalColor.stride;
pixelsgray = (char *) pixelsgray + infogray.stride;
}
LOGI("unlocking pixels");
AndroidBitmap_unlockPixels(env, bmOriginal);
AndroidBitmap_unlockPixels(env, bmGray);
}
編寫Android.mk文件,該文件主要是指明要使用的.so文件,並且生成我們自己的.so文件
LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := PhotoProcessing LOCAL_SRC_FILES := PhotoProcessing.cpp LOCAL_LDLIBS := -llog -ljnigraphics include $(BUILD_SHARED_LIBRARY)關鍵的一些代碼就是這些了,其中處理的灰度算法可能不是非常優化,這其中處理RGB565部分是我自己根據圖像處理中灰度的定義所寫的,其中也要感謝孫志海大哥對我的幫助 !!
可以說使用這種方法還是比較簡易的,但是,似乎仍沒解決我一開頭說道的問題,即這種方式僅僅是提升了程序的效率,但依然需要在UI線程中更新界面,這裡也可以使用SurfaceVIew來進行異步的更新界面,但是這裡,我想知道,在不修改android系統源碼情況下,NDK的極限,即它能否直接控制View的surface,使其不通過java代碼就直接把界面刷新呢?這個可能會涉及到Linux的文件權限問題,以及需要翻閱android系統源碼。
望對這個方面感興趣的朋友,能夠和我一起交流,或者能夠給我一些建議。我的QQ是835060947,也可以發郵件給我。
