android 源码下的JNI编译

本文仅作为记录之用

案例: BitmapBlur 图片虚化库.

编译JAVA

package com.a.b.c;

import android.content.Context;
import android.graphics.Bitmap;
import android.os.Build.VERSION;
import android.renderscript.Allocation;
import android.renderscript.Element;
import android.renderscript.RenderScript;
import android.renderscript.ScriptIntrinsicBlur;

public class BitmapBlur {
	static{
		System.loadLibrary("BitmapBlur");
	}
	
	/**
	 * blur src bitmap
	 * @param src
	 * @param cxt
	 * @param radius 0 <= radius <= 25
	 * @return
	 */
	public static Bitmap getBlurBitmap(Bitmap src, Context cxt, int radius){
		return getBlurBitmap(src, cxt, radius, false);
	}
	
	/**
	 * blur src bitmap by JNI
	 * @param src
	 * @param radius
	 * @return
	 */
	public static Bitmap getBlurBitmapJNI(Bitmap src, int radius){
		return getBlurBitmap(src, null, radius, true);
	}
	
	/**
	 * blur src, if SDK > 16, use SDK, else use JNI;
	 * @param src
	 * @param cxt
	 * @param radius radius 0 <= radius <= 25
	 * @param forceJNI
	 * @return
	 */
	public static Bitmap getBlurBitmap(Bitmap src, Context cxt, int radius, boolean forceJNI){
		if (VERSION.SDK_INT > 16 && !forceJNI) {
            Bitmap bitmap = src.copy(src.getConfig(), true);

            final RenderScript rs = RenderScript.create(cxt);
            final Allocation input = Allocation.createFromBitmap(rs, src, Allocation.MipmapControl.MIPMAP_NONE,
                    Allocation.USAGE_SCRIPT);
            final Allocation output = Allocation.createTyped(rs, input.getType());
            final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));
            script.setRadius(radius /* e.g. 3.f */);
            script.setInput(input);
            script.forEach(output);
            output.copyTo(bitmap);
            return bitmap;
        }else{
        	blur(src, radius);
        }
		return src;
	}
	public native static void blurArray(int[] bm, int w, int h, int radius);
	public native static void blur(Bitmap bm, int radius);
}

拷贝BitmapBlur.class到JNI目录下:

mkdir -p com/a/b/c/

cp xxx/BitmapBlur.class com/a/b/c/

生成JNI 头文件

javah -classpath . -d jni com.a.b.c.BitmapBlur

生成jni/com_a_b_c_BitmapBlur.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_a_b_c_BitmapBlur */

#ifndef _Included_com_a_b_c_BitmapBlur
#define _Included_com_a_b_c_BitmapBlur
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_a_b_c_BitmapBlur
 * Method:    blurArray
 * Signature: ([IIII)V
 */
JNIEXPORT void JNICALL Java_com_a_b_c_BitmapBlur_blurArray
  (JNIEnv *, jclass, jintArray, jint, jint, jint);

/*
 * Class:     com_a_b_c_BitmapBlur
 * Method:    blur
 * Signature: (Landroid/graphics/Bitmap;I)V
 */
JNIEXPORT void JNICALL Java_a_b_c_BitmapBlur_blur
  (JNIEnv *, jclass, jobject, jint);

#ifdef __cplusplus
}
#endif
#endif

编写CPP文件com_a_b_c_BitmapBlur.cpp

/* DO NOT EDIT THIS FILE - it is machine generated */

#include <com_a_b_c_BitmapBlur.h>
#include <android/bitmap.h>
#include <android/log.h>
#include <blur.c>
#include <stdio.h>

JNIEXPORT void JNICALL Java_a_b_c_BitmapBlur_blurArray
  (JNIEnv *env, jclass thiz, jintArray arrIn, jint w, jint h, jint r)
{
	jint *pix;
	pix = env->GetIntArrayElements(arrIn, 0);
	if (pix == NULL)
		return;
	//Start
	pix = blurIntArray(pix, w, h, r);
	//End
	//int size = w * h;
	//jintArray result = env->NewIntArray(size);
	//env->SetIntArrayRegion(result, 0, size, pix);
	env->ReleaseIntArrayElements(arrIn, pix, 0);
	//return result;
}


JNIEXPORT void JNICALL Java_a_b_c_BitmapBlur_blur
  (JNIEnv *env, jclass thiz, jobject bitmapIn, jint r)
{

/***************************************/
	AndroidBitmapInfo infoIn;

	void* pixelsIn;
	int ret;

	// Get image info
	if ((ret = AndroidBitmap_getInfo(env, bitmapIn, &infoIn)) < 0)
		return;
	// Check image
	if (infoIn.format != ANDROID_BITMAP_FORMAT_RGBA_8888)
		return;
	// Lock all images
	if ((ret = AndroidBitmap_lockPixels(env, bitmapIn, &pixelsIn)) < 0) {
		//AndroidBitmap_lockPixels failed!
	}
	//height width
	int h = infoIn.height;
	int w = infoIn.width;

	//Start
	pixelsIn = blurIntArray((int*)pixelsIn, w, h, r);
	//End

	// Unlocks everything
	AndroidBitmap_unlockPixels(env, bitmapIn);
/**********************************/
}

blur.c

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
#include <math.h>
#include <android/bitmap.h>
#include <android/log.h>
#include <stdio.h>

/* Header for class com_a_b_c_BitmapBlur */
#include<malloc.h>

#define ABS(a) ((a)<(0)?(-a):(a))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))

/*
 * Class:     com_a_b_c_BitmapBlur
 * Method:    blur
 * Signature: (Landroid/graphics/Bitmap;)V
 */

static int* blurIntArray(int* pix, int w, int h, int radius) {
    int wm = w - 1;
    int hm = h - 1;
    int wh = w * h;
    int div = radius + radius + 1;

    int *r = (int *)malloc(wh * sizeof(int));
    int *g = (int *)malloc(wh * sizeof(int));
    int *b = (int *)malloc(wh * sizeof(int));
    int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;

    int *vmin = (int *)malloc(MAX(w,h) * sizeof(int));

    int divsum = (div + 1) >> 1;
    divsum *= divsum;
    int *dv = (int *)malloc(256 * divsum * sizeof(int));
    for (i = 0; i < 256 * divsum; i++) {
        dv[i] = (i / divsum);
    }

    yw = yi = 0;

    int(*stack)[3] = (int(*)[3])malloc(div * 3 * sizeof(int));
    int stackpointer;
    int stackstart;
    int *sir;
    int rbs;
    int r1 = radius + 1;
    int routsum, goutsum, boutsum;
    int rinsum, ginsum, binsum;

    for (y = 0; y < h; y++) {
        rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
        for (i = -radius; i <= radius; i++) {
            p = pix[yi + (MIN(wm, MAX(i, 0)))];
            sir = stack[i + radius];
            sir[0] = (p & 0xff0000) >> 16;
            sir[1] = (p & 0x00ff00) >> 8;
            sir[2] = (p & 0x0000ff);

            rbs = r1 - ABS(i);
            rsum += sir[0] * rbs;
            gsum += sir[1] * rbs;
            bsum += sir[2] * rbs;
            if (i > 0) {
                rinsum += sir[0];
                ginsum += sir[1];
                binsum += sir[2];
            }
            else {
                routsum += sir[0];
                goutsum += sir[1];
                boutsum += sir[2];
            }
        }
        stackpointer = radius;

        for (x = 0; x < w; x++) {

            r[yi] = dv[rsum];
            g[yi] = dv[gsum];
            b[yi] = dv[bsum];

            rsum -= routsum;
            gsum -= goutsum;
            bsum -= boutsum;

            stackstart = stackpointer - radius + div;
            sir = stack[stackstart % div];

            routsum -= sir[0];
            goutsum -= sir[1];
            boutsum -= sir[2];

            if (y == 0) {
                vmin[x] = MIN(x + radius + 1, wm);
            }
            p = pix[yw + vmin[x]];

            sir[0] = (p & 0xff0000) >> 16;
            sir[1] = (p & 0x00ff00) >> 8;
            sir[2] = (p & 0x0000ff);

            rinsum += sir[0];
            ginsum += sir[1];
            binsum += sir[2];

            rsum += rinsum;
            gsum += ginsum;
            bsum += binsum;

            stackpointer = (stackpointer + 1) % div;
            sir = stack[(stackpointer) % div];

            routsum += sir[0];
            goutsum += sir[1];
            boutsum += sir[2];

            rinsum -= sir[0];
            ginsum -= sir[1];
            binsum -= sir[2];

            yi++;
        }
        yw += w;
    }
    for (x = 0; x < w; x++) {
        rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
        yp = -radius * w;
        for (i = -radius; i <= radius; i++) {
            yi = MAX(0, yp) + x;

            sir = stack[i + radius];

            sir[0] = r[yi];
            sir[1] = g[yi];
            sir[2] = b[yi];

            rbs = r1 - ABS(i);

            rsum += r[yi] * rbs;
            gsum += g[yi] * rbs;
            bsum += b[yi] * rbs;

            if (i > 0) {
                rinsum += sir[0];
                ginsum += sir[1];
                binsum += sir[2];
            }
            else {
                routsum += sir[0];
                goutsum += sir[1];
                boutsum += sir[2];
            }

            if (i < hm) {
                yp += w;
            }
        }
        yi = x;
        stackpointer = radius;
        for (y = 0; y < h; y++) {
            // Preserve alpha channel: ( 0xff000000 & pix[yi] )
            pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16) | (dv[gsum] << 8) | dv[bsum];

            rsum -= routsum;
            gsum -= goutsum;
            bsum -= boutsum;

            stackstart = stackpointer - radius + div;
            sir = stack[stackstart % div];

            routsum -= sir[0];
            goutsum -= sir[1];
            boutsum -= sir[2];

            if (x == 0) {
                vmin[y] = MIN(y + r1, hm) * w;
            }
            p = x + vmin[y];

            sir[0] = r[p];
            sir[1] = g[p];
            sir[2] = b[p];

            rinsum += sir[0];
            ginsum += sir[1];
            binsum += sir[2];

            rsum += rinsum;
            gsum += ginsum;
            bsum += binsum;

            stackpointer = (stackpointer + 1) % div;
            sir = stack[stackpointer];

            routsum += sir[0];
            goutsum += sir[1];
            boutsum += sir[2];

            rinsum -= sir[0];
            ginsum -= sir[1];
            binsum -= sir[2];

            yi += w;
        }
    }

    free(r);
    free(g);
    free(b);
    free(vmin);
    free(dv);
    free(stack);
    return(pix);
}

编写Android.mk文件

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := libBitmapBlur
LOCAL_SRC_FILES := com_a_b_c_BitmapBlur.cpp
LOCAL_SHARED_LIBRARIES := \
        libandroid_runtime \
        libcutils \
        libjnigraphics

include $(BUILD_SHARED_LIBRARY)

普通的JNI编译到此结束.

接下来只需要通过mm / mmm命令编译即可生成相应lib库.

以下补充一些遇到的问题:

1. 引用让部lib库.

    在编译当前的lib时, 需要依赖到libExt1.so, libExt2.so, 我们把两个lib库放在编译目录的lib/目录下, 同时, 新建lib/Android.mk文件, 内容如下:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := libExt1.so
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_STEM := $(LOCAL_MODULE)
LOCAL_SRC_FILES := $(LOCAL_MODULE)
LOCAL_MODULE_SUFFIX := 
include $(BUILD_PREBUILT)

include $(CLEAR_VARS)
LOCAL_MODULE := libExt2.so
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_STEM := $(LOCAL_MODULE)
LOCAL_SRC_FILES := $(LOCAL_MODULE)
LOCAL_MODULE_SUFFIX := 
include $(BUILD_PREBUILT)

在需要编译的模块的Android.mk中, 添加如下:

LOCAL_SHARED_LIBRARIES := libExt1 libExt2

在这之前曾错误的使用了: include $(call all-subdir-makefiles), 导致编译出现很多问题:

最常见的make: *** No rule to make target 'packages/jni/BTP_S80/lib/com_example_testscanprn_Printer.cpp', needed by 'out/target/product/XXX/obj/SHARED_LIBRARIES/libScanPrnWrap_intermediates/com_example_testscanprn_Printer.o'.  Stop.

2. 源码文件,

LOCAL_SRC_FILES := com_a_b_c_BitmapBlur.cpp

使用错误的文件名, 也同样可以编译通过, 并生成so库, 但so库在JAVA调用时, 会提示

java.lang.UnsatisfiedLinkError: No implementation found for 后面紧跟的是函数名.

3. 关于javah.

javah -classpath . -d jni a.b.c.Printer 这里需注意classpath后面的参数

如, 刚开始是把native函数写在Activity中, 后面发现, 会出现找不到android.app.Activity类的错误

网上也有对应的解决方案, 但没时间去细细研究, 建议, 把native函数放在单的类中定义, 这样用javah生成.h文件时会少走些弯路.