title: Android keyevent抓图，使用jpeg565对数据压缩 date: '2013-03-07' description: 前端时间为了做一个测试工具,做了一个快捷抓图功能 tags: [Android,jpeglib] categories: [technology]

实现功能

使用poll池方法监测event3，event5和对从FB_DEVICE获得的图像数据进行jpeg压缩，压缩图像由之前的2700k缩小为89k，压缩比显而易见（30倍）。

效果图

抓图实现

从FB_DEVICE "/dev/graphics/fb0"获得图像的原始数据，色彩数据分为头和rgba数据，在 函数jpg_screen_capture里case 16：中我对原始数据进行了处理，将rgba8888的数据转换为rgb565的数据，最后用generateJPEG对数据进行jpeg compress，具体的可以见capture_jpg.c代码 * 这里要注意的一点是在读取fb_var.xres值必须为2^5=16的倍数，不够的要补足，也就是如下代码：

if((fb_var.xres&0x1F)==0)
  fb->w = fb_var.xres;
else
  fb->w =((fb_var.xres>>5)+1)<<5;

这样可以避免在抓图时出现像素移位，该问题在fb0的图像像素宽不是16的倍数时出现。

capture_jpg.c

/*=============================================================================
#     FileName: capture_jpg.c
#         Desc: capture jgp screenshoot 
#       Author: Lee Meng
#        Email: leaveboy@gmail.com
#     HomePage: http://leaveboy.is-programmer.com/
#      Version: 0.0.1
#   LastChange: 2013-01-15 09:33:23
#      History:
=============================================================================*/
#include <string.h>  
#include <stdlib.h>

#include <math.h>  
#include <stdio.h>  
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

typedef uint8_t BYTE;  
#define true 1  
#define false 0

#include <jpeglib.h>

#define FB_DEVICE "/dev/graphics/fb0"
static int g_fd;

typedef struct
{
    int w;    /* width */
    int h;    /* high */
    int bpp;  /* bits per pixel */
    unsigned char *fbmem;
}screen;

static int init_fb(screen *fb)
{
    if ((g_fd = open(FB_DEVICE, O_RDWR)) < 0)
    { 
        fprintf(stderr, "Open %s failed:%s\n", FB_DEVICE, strerror(errno));
        return -1; 
    }

    struct fb_var_screeninfo fb_var;
    struct fb_fix_screeninfo fb_fix;

    if (ioctl(g_fd, FBIOGET_VSCREENINFO, &fb_var) < 0)
    { 
        fprintf(stderr, "fb ioctl failed:%s\n", strerror(errno));
        return -1; 
    }   
    /*
         if (ioctl(g_fd, FBIOGET_FSCREENINFO, &fb_fix) < 0)
         { 
         fprintf(stderr, "fb ioctl failed:%s\n", strerror(errno));
         return -1; 
         }   
         */
    //fb->w   = fb_var.xres;
    if((fb_var.xres&0x1F)==0)
        fb->w = fb_var.xres;
    else
        fb->w =((fb_var.xres>>5)+1)<<5;
    fb->h   = fb_var.yres;
    fb->bpp = fb_var.bits_per_pixel;
    //  printf("capture_log %d, %d, %d, %d\n", fb_var.xres_virtual, fb_var.yres_virtual, fb_var.xoffset, fb_var.yoffset);
    //  printf("capture_log %d\n", fb_fix.line_length);
#if 1
    printf("width:%d\thigh:%d\tbpp:%d\n",fb->w, fb->h, fb->bpp);
#endif
    fb->fbmem = mmap(0, fb->w * fb->h * fb->bpp /8,PROT_READ | PROT_WRITE, MAP_SHARED, g_fd, 0);
    if (fb->fbmem == MAP_FAILED)
    {
        fprintf(stderr, "fb mmap failed:%s\n", strerror(errno));
        return -1;
    }

    close(g_fd);
    return 0;
}

int term_fb(screen *fb)
{
    munmap(fb->fbmem, fb->w * fb->h * fb->bpp / 8);
    return 0;
}

static int generateJPEG(BYTE* data,int w, int h, const char* outfilename)  
{  
    int nComponent = 3;

    struct jpeg_compress_struct jcs;

    struct jpeg_error_mgr jem;

    jcs.err = jpeg_std_error(&jem);   
    jpeg_create_compress(&jcs);

    FILE* f=fopen(outfilename,"wb");  
    if (f==NULL)   
    {  
        free(data);  
        return 0;  
    }  
    jpeg_stdio_dest(&jcs, f);  
    jcs.image_width = w;   
    jcs.image_height = h;  
    jcs.input_components = nComponent;  
    if (nComponent==1)  
        jcs.in_color_space = JCS_GRAYSCALE; 
    else   
        jcs.in_color_space = JCS_RGB;

    jpeg_set_defaults(&jcs);      
    jpeg_set_quality (&jcs, 80, true);

    jpeg_start_compress(&jcs, TRUE);

    JSAMPROW row_pointer[1];
    int row_stride;

    row_stride = jcs.image_width*nComponent;

    while (jcs.next_scanline < jcs.image_height) {  
        row_pointer[0] = & data[jcs.next_scanline*row_stride];

        jpeg_write_scanlines(&jcs, row_pointer, 1);  
    }

    jpeg_finish_compress(&jcs);  
    jpeg_destroy_compress(&jcs);  
    fclose(f);

    return 1;  
}

//int main(void)
extern int jpg_screen_capture(char * file_name)
{  
    int i = 0, j = 0;
    int w = 0, h = 0;
    int ret = 0;
    unsigned char *p;
    screen fb_screen;

    init_fb(&fb_screen);

    w = fb_screen.w;
    h = fb_screen.h;

    p = (unsigned char *)malloc(w * h * 3);

    printf("0x%x %x %x %x\n", *fb_screen.fbmem, *(fb_screen.fbmem + 1), \
            *(fb_screen.fbmem + 2), *(fb_screen.fbmem + 3));

    short *cursor = (short*)fb_screen.fbmem;
    switch(fb_screen.bpp)
    {
        case 32:
            for(i = 0; i < h; i++)
            {
                for(j = 0; j < w; j++)
                {
                    *(p + (i * w + j) * 3 + 0) = *(fb_screen.fbmem + (i * w + j) * 4 + 0);
                    *(p + (i * w + j) * 3 + 1) = *(fb_screen.fbmem + (i * w + j) * 4 + 1);
                    *(p + (i * w + j) * 3 + 2) = *(fb_screen.fbmem + (i * w + j) * 4 + 2);
                }
            }
            break;

        case 16:
            while(i<w*h)
            {
                short pixel = *cursor;     
                int r = (pixel & 0xF800) << 8; 
                int g = (pixel & 0x7E0) << 5;  
                int b = (pixel & 0x1F) << 3;
                int color = 0xFF000000 | r | g | b;

                *(p + 3 * i + 0) = (unsigned char)(color>>16 &0xFF);
                *(p + 3 * i + 1) = (unsigned char)(color>>8  &0xFF);
                *(p + 3 * i + 2) = (unsigned char)(color>>0  &0xFF);
                i++;
                cursor++;
            }
            break;

        default:
            printf("not support bpp %d\n",fb_screen.bpp);
            return -1;
            break;
    }

    //  ret = generateJPEG(p, fb_screen.w, fb_screen.h, "/data/test/test.jpg");  
    ret = generateJPEG(p, fb_screen.w, fb_screen.h, file_name);

    term_fb(&fb_screen);    
    free(p);
    return ret;
}

监听keyevent事件

这里为了避免单按键对使用造成影响，需同时监听两个keyevent 分别为event3 和 event5，对这两个事件的监听采用了无阻塞方式，在poll池中对两个event进行检测，通过event.code 和 event.value 区别按键（那个按键）动作（按下/松开）,最后通过fork_sound()

/*=============================================================================
#     FileName: getevent.c
#         Desc: get events of powerkey and volume + 
#       Author: Lee Meng
#        Email: leaveboy@gmail.com
#     HomePage: http://leaveboy.is-programmer.com/
#      Version: 0.0.1
#   LastChange: 2013-01-15 09:32:53
#      History:
=============================================================================*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <sys/poll.h>
#include <linux/input.h>

#define TIME_DELAY   6000 
#define IN_FILES  2
#define SAVE_PATH "/data/logs"
#define SOUND_PATH "system/media/audio/alarms/Alarm_Buzzer.ogg"

struct timeval tv,tv_event3={0L, 0L},tv_event5={0L, 0L};
static unsigned char  event3_down = 0x00;//
static unsigned char  event5_down = 0x00;
struct input_event event;

static void  fork_sound(void)
{
  pid_t pid = fork();
  if (pid == 0) {
    execl("/system/bin/stagefright", "stagefright", "-o", "-a", SOUND_PATH, NULL);
    /*execl("/system/bin/busybox", "busybox", "tar", "cvf", "/mnt/sdcard/logs.tar",SAVE_PATH, NULL);*/
    //execl("/system/bin/busybox", "busybox", "bzip", "-9", "/mnt/sdcard/logs.tar",NULL);
  }
}
/*int main(void) {*/
extern int event_capture_jpg(void) {
  int pollres;
  struct pollfd  fds[2];
  struct tm *p;
  time_t now;
  char capture_name[128];

  int i, real_read;
  printf("sizeof(struct input_event) = %d\n", sizeof(struct input_event));
  fds[0].fd  = open("/dev/input/event3", O_RDONLY|O_NONBLOCK);//volume button
  fds[1].fd  = open("/dev/input/event5", O_RDONLY|O_NONBLOCK);//power button

  for (i = 0; i<IN_FILES; i++){
    if ( fds[i].fd < 0 ) return -1;
    fds[i].events = POLLIN;
  }
  while(1){
    pollres = poll(fds,IN_FILES,TIME_DELAY);
    for (i = 0; i< IN_FILES; i++){
      if (fds[i].revents){
        real_read = read(fds[i].fd, &event, sizeof(event));
        if(real_read < (int)sizeof(event)) {
          fprintf(stderr, "could not get event\n");
          break;
        }
        time(&now);
        p = localtime(&now);
        sprintf(capture_name,"%s/%d-%d-%d_%d-%d-%d.jpg",
            SAVE_PATH,
            1900+p->tm_year, 1+p->tm_mon, p->tm_mday, 
            p->tm_hour, p->tm_min, p->tm_sec);
        printf("%d %u %u %u\n", i, event.type, event.code, event.value);

        if (i == 0x01 && event.type == 0x01 && event.code == 0x6B && event.value == 0x00)
          event5_down = 0x00;

        if (i == 0x00 && event.type == 0x01 && event.code == 0x73 && event.value == 0x00)
          event3_down = 0x00;

        if (i == 0x01 && event.type == 0x01 && event.code == 0x6B && event.value == 0x01)
        {
          event5_down = 0x01;
          if(event3_down&event5_down)
          {
            jpg_screen_capture(capture_name);
            fork_sound();
            printf("Lee Meng capture jpg:%s\n",capture_name);
          }
        }

        if (i == 0x00 && event.type == 0x01 && event.code == 0x73 && event.value == 0x01)
        {
          event3_down = 0x01;
          if(event3_down&event5_down)
          {
            printf("Lee Meng capture jpg:%s\n",capture_name);
            jpg_screen_capture(capture_name);
            fork_sound();
          }
        }

      } 
    }
    //no sleep
  }

  for(i=0;i<2;i++){
    if(fds[i].fd > 0){
      close(fds[i].fd);
      fds[i].fd = -1;
    }   
  }
  return 0;
}

main函数及Android.mk

main.c

#include <stdio.h>

int main(void)
{
  while(1)
  event_capture_jpg();
}

Android.mk

LOCAL_PATH := $(my-dir)

commonSources  :=

commonIncludes := $(TARGET_OUT_HEADERS)/common/inc

commonSharedLibraries :=  liboncrpc
commonSharedLibraries +=  libnv
commonSharedLibraries +=  libcutils libxml2 libicuuc
commonSharedLibraries +=  libutils
commonSharedLibraries +=  libjpeg libc

include $(CLEAR_VARS)
LOCAL_MODULE := qlogd
LOCAL_CFLAGS := $(commonCflags)

LOCAL_C_INCLUDES := $(call include-path-for, system-core)/cutils
LOCAL_C_INCLUDES += $(commonIncludes)
LOCAL_C_INCLUDES += $(LOCAL_PATH)
LOCAL_C_INCLUDES += external/jpeg
LOCAL_SRC_FILES := main.c getevent.c capture_jpg.c
LOCAL_MODULE_TAGS := optional eng
LOCAL_SHARED_LIBRARIES += $(commonSharedLibraries) 
LOCAL_MODULE_PATH := $(TARGET_OUT_OPTIONAL_EXECUTABLES)
include $(BUILD_EXECUTABLE)

这四个文件放到Android工程下面vendor/qlogd目录下，mmm编译之后就可以在/system/xbin/找到qlogd，将qlogd push到手机上相应的目录/system/xbin/，添加可以执行权限

chmod 777 qlogd

然后运行

/system/xbin/qlogd&

按下power键和音量-键,就可以听到Bi Bi Bi的提示音了。