Android 使用NDK处理BItmap及如何通过C/C++直接控制View的suface显示,学习笔记及方向

浏览数：35 / 时间：2015年06月11日

最近的学习真的比较困难,因为学习了SDK开发项目后,做了一些简单的项目后,觉得在UI线程中加载较多图片时,总会出现卡顿的感觉,特别是手指滑动下拉时,这种卡顿更易察觉到,而java的结构化开发能力确实是很强大的,使用java开发确实是一件非常享受的事情,但是java在一些高密度的计算中是没有什么优势的,在享受内存自动回收时也会遇到一些不如意的事。任何语言或事物,总会有优缺点,这是java如此简单易用的一个副作用。所以为了不使java的副作用危害到开发者使用java,java产生了一种非常有吸引力的的技术JNI技术,这种技术可以让Java调用C/C++和其他的语言所写的程序。而这种技术也在android中得以支持--NDK, NDK提供了一系列的工具，帮助开发者快速开发C（或C++）的动态库，并能自动将so和java应用一起打包成apk,使用起来非常方便。

说了一堆的废话,接下来记录下自己最近所学习到的东西,可以说NDK重要的学习资料之一就是android的官方网站提供的资料,包括下载了NDK后,也能看到一些简单的使用了NDK的项目源码,这些源码能让我们知道android官方建议我们如何使用NDK,甚至可以用纯C/C++语言开发应用,但这并不是我感兴趣的,具体原因就不说了。

按照官方的使用方式还是比较简单的,这里写了一个用C语言提取照片灰度图的函数,并在java中调用

先写java代码

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工具得到头文件PhotoProcessingActivity.h并且添加处理图片所需的一些头文件,这些头文件都是NDK中的include中自带的,使用时可以把把该文件夹链接进去

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_photoprocessing_activity_PhotoProcessingActivity */
#include <android/bitmap.h>
#include <android/log.h>
#include <math.h>
#include <string.h>


#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
接着编写C代码

#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);
}
编写Android.mk文件,该文件主要是指明要使用的.so文件,并且生成我们自己的.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)
关键的一些代码就是这些了,其中处理的灰度算法可能不是非常优化,这其中处理RGB565部分是我自己根据图像处理中灰度的定义所写的,其中也要感谢孙志海大哥对我的帮助 !!

可以说使用这种方法还是比较简易的,但是,似乎仍没解决我一开头说道的问题,即这种方式仅仅是提升了程序的效率,但依然需要在UI线程中更新界面,这里也可以使用SurfaceVIew来进行异步的更新界面,但是这里,我想知道,在不修改android系统源码情况下,NDK的极限,即它能否直接控制View的surface,使其不通过java代码就直接把界面刷新呢?这个可能会涉及到Linux的文件权限问题,以及需要翻阅android系统源码。

望对这个方面感兴趣的朋友,能够和我一起交流,或者能够给我一些建议。我的QQ是835060947,也可以发邮件给我。




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