【JNI】 Android调用JNI的进阶实例（摄像头预览数据转码RGB播放）
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前一篇的博文介绍了：Android调用JNI的简单实例（附详细步骤），现在带来一个进阶版的，虽然时间隔得有点久远。
这里要说下，尽量不要用Java写编解码的东西，就算你是大神，你写的出来，但那也是不实用的，就像切西瓜一样，拿一把削水果刀去切西瓜，肯定比不上用西瓜刀方便吧，还是老老实实写个JNI调用得了，也不复杂C/C++方便的很，当然，这里不是说Java不行，语言只是工具，做什么事情用什么语言，没必要硬着头皮往上顶对吧。纯属个人观点，大神可以无视。
好了进入正题，该实例主要内容：开启摄像头预览，将获取到的视频帧YUV数据，通过JNI调用C的转码函数转为RGB类型数据然后返回，在自定义控件上绘制播放。
1、工程结构：
该工程是在之前的SimpleJni实例上进行修改的，简单描述一下功能：
CameraEngineActivity主界面，用于加载控件及渲染等；
CameraView摄像头预览控件，用于预览及捕获视频帧YUV数据；
ImageUtilEngine声明调用C函数的接口类，声明native的C函数；
SporeRender渲染画面类，用于绘制图像；
Texture2D图像优化类，用于优化图像纹理；
Demo地址：
2、新建java调用C函数的接口类
- package com.eric.complexjni;
-
-
-
-
- public class ImageUtilEngine {
- static {
- System.loadLibrary("");
- }
-
- public native int[] decodeYUV420SP(byte[] buf, int width, int heigth);
- }
命令窗口：Win+R运行cmd，cd进入到eclipse工作空间中ComplexJni工程目录，
输入javah -classpath bin/classes -d jni com.eric.complexjni.ImageUtilEngine编译接口类
编译完成后，刷新工程，就可以看到工程中自动创建了jni文件夹，其中包含编译好的.h头文件
4、在jni目录下新建com_eric_complexjni_ImageUtilEngine.h
- #include <jni.h>
- #include <stdlib.h>
- #include <com_eric_complexjni_ImageUtilEngine.h>
- #include <android/log.h>
- #include <android/bitmap.h>
- #include <math.h>
- #define LOG_TAG "Spore.meitu"
- #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
- #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
-
- int min(int x, int y) {
- return (x <= y) ? x : y;
- }
- int max(int x,int y){
- return (x >= y) ? x : y;
- }
- int alpha(int color) {
- return (color >> 24) & 0xFF;
- }
- int red(int color) {
- return (color >> 16) & 0xFF;
- }
- int green(int color) {
- return (color >> 8) & 0xFF;
- }
- int blue(int color) {
- return color & 0xFF;
- }
- int ARGB(int alpha, int red, int green, int blue) {
- return (alpha << 24) | (red << 16) | (green << 8) | blue;
- }
-
- #include <unistd.h>
- #include <stdio.h>
- #include <fcntl.h>
- #include <linux/fb.h>
- #include <sys/mman.h>
- inline static unsigned short int make16color(unsigned char r, unsigned char g, unsigned char b)
- {
- return (
- (((r >> 3) & 31) << 11) |
- (((g >> 2) & 63) << 5) |
- ((b >> 3) & 31) );
- }
-
- int framebuffer_main()
- {
- LOGI("framebuffer code");
- int fbfd = 0;
- struct fb_var_screeninfo vinfo;
- struct fb_fix_screeninfo finfo;
- long int screensize = 0;
- char *fbp = 0;
- int x = 0, y = 0;
- int guage_height = 20, step = 10;
- long int location = 0;
-
- LOGI("framebuffer code 1");
- fbfd = open("/dev/graphics/fb0", O_RDWR);
- LOGI("framebuffer code 2");
- if (!fbfd) {
- LOGI("Error: cannot open framebuffer device.\n");
- exit(1);
- }
- LOGI("The framebuffer device was opened successfully.\n");
-
- if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
- LOGI("Error reading fixed information.\n");
- exit(2);
- }
-
- if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
- LOGI("Error reading variable information.\n");
- exit(3);
- }
- LOGI("sizeof(unsigned short) = %d\n", sizeof(unsigned short));
- LOGI("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
- LOGI("xoffset:%d, yoffset:%d, line_length: %d\n", vinfo.xoffset,
- vinfo.yoffset, finfo.line_length);
-
- screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
-
- fbp = (char *) mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
- fbfd, 0);
- if ((int) fbp == -1) {
- LOGI("Error: failed to map framebuffer device to memory.\n");
- exit(4);
- }
- LOGI("The framebuffer device was mapped to memory successfully.\n");
-
- memset(fbp, 0, screensize);
-
- y = (vinfo.yres - guage_height) / 2 - 2;
- for (x = step - 2; x < vinfo.xres - step + 2; x++) {
- location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) + (y
- + vinfo.yoffset) * finfo.line_length;
- *((unsigned short int*) (fbp + location)) = 255;
- }
- y = (vinfo.yres + guage_height) / 2 + 2;
- for (x = step - 2; x < vinfo.xres - step + 2; x++) {
- location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) + (y
- + vinfo.yoffset) * finfo.line_length;
- *((unsigned short int*) (fbp + location)) = 255;
- }
- x = step - 2;
- for (y = (vinfo.yres - guage_height) / 2 - 2; y < (vinfo.yres
- + guage_height) / 2 + 2; y++) {
- location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) + (y
- + vinfo.yoffset) * finfo.line_length;
- *((unsigned short int*) (fbp + location)) = 255;
- }
- x = vinfo.xres - step + 2;
- for (y = (vinfo.yres - guage_height) / 2 - 2; y < (vinfo.yres
- + guage_height) / 2 + 2; y++) {
- location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) + (y
- + vinfo.yoffset) * finfo.line_length;
- *((unsigned short int*) (fbp + location)) = 255;
- }
-
- for (x = step; x < vinfo.xres - step; x++) {
- for (y = (vinfo.yres - guage_height) / 2; y < (vinfo.yres
- + guage_height) / 2; y++) {
- location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) + (y
- + vinfo.yoffset) * finfo.line_length;
- if (vinfo.bits_per_pixel == 32) {
- *(fbp + location) = 100;
- *(fbp + location + 1) = 15 + (x - 100) / 2;
- *(fbp + location + 2) = 200 - (y - 100) / 5;
- *(fbp + location + 3) = 0;
- } else {
- unsigned char b = 255 * x / (vinfo.xres - step);
- unsigned char g = 255;
- unsigned char r = 255;
- unsigned short int t = make16color(r, g, b);
- *((unsigned short int*) (fbp + location)) = t;
- }
- }
-
-
- usleep(200);
- }
-
- munmap(fbp, screensize);
- close(fbfd);
- return 0;
- }
-
- int r_v_table[256],g_v_table[256],g_u_table[256],b_u_table[256],y_table[256];
- int r_yv_table[256][256],b_yu_table[256][256];
- int inited = 0;
-
- void initTable()
- {
- if (inited == 0)
- {
-
- inited = 1;
- int m = 0,n=0;
- for (; m < 256; m++)
- {
- r_v_table[m] = 1634 * (m - 128);
- g_v_table[m] = 833 * (m - 128);
- g_u_table[m] = 400 * (m - 128);
- b_u_table[m] = 2066 * (m - 128);
- y_table[m] = 1192 * (m - 16);
- }
- int temp = 0;
- for (m = 0; m < 256; m++)
- for (n = 0; n < 256; n++)
- {
- temp = 1192 * (m - 16) + 1634 * (n - 128);
- if (temp < 0) temp = 0; else if (temp > 262143) temp = 262143;
- r_yv_table[m][n] = temp;
-
- temp = 1192 * (m - 16) + 2066 * (n - 128);
- if (temp < 0) temp = 0; else if (temp > 262143) temp = 262143;
- b_yu_table[m][n] = temp;
- }
- }
- }
-
- jintArray Java_com_spore_ImageUtilEngine_decodeYUV420SP(JNIEnv * env,
- jobject thiz, jbyteArray buf, jint width, jint height) {
- jbyte * yuv420sp = (*env)->GetByteArrayElements(env, buf, 0);
-
- int frameSize = width * height;
- jint rgb[frameSize];
-
- initTable();
-
- int i = 0, j = 0,yp = 0;
- int uvp = 0, u = 0, v = 0;
- for (j = 0, yp = 0; j < height; j++)
- {
- uvp = frameSize + (j >> 1) * width;
- u = 0;
- v = 0;
- for (i = 0; i < width; i++, yp++)
- {
- int y = (0xff & ((int) yuv420sp[yp]));
- if (y < 0)
- y = 0;
- if ((i & 1) == 0)
- {
- v = (0xff & yuv420sp[uvp++]);
- u = (0xff & yuv420sp[uvp++]);
- }
-
-
-
-
-
- int y1192 = y_table[y];
- int r = r_yv_table[y][v];
- int g = (y1192 - g_v_table[v] - g_u_table[u]);
- int b = b_yu_table[y][u];
-
-
- if (g < 0) g = 0; else if (g > 262143) g = 262143;
-
-
-
-
-
- rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) & 0xff);
- }
- }
-
- jintArray result = (*env)->NewIntArray(env, frameSize);
- (*env)->SetIntArrayRegion(env, result, 0, frameSize, rgb);
- (*env)->ReleaseByteArrayElements(env, buf, yuv420sp, 0);
- return result;
- }
- LOCAL_PATH := $(call my-dir)
-
- include $(CLEAR_VARS)
-
- LOCAL_SRC_FILES:= com_eric_complexjni_ImageUtilEngine.c
- LOCAL_C_INCLUDES := $(JNI_H_INCLUDE)
- LOCAL_SHARED_LIBRARIES := libutils
- LOCAL_PRELINK_MODULE := false
- LOCAL_MODULE := SimpleJni
- LOCAL_LDLIBS := -llog -ljnigraphics
-
- include $(BUILD_SHARED_LIBRARY)
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