本文介绍了一种在Android上使用C语言实现截屏的方法，包括读取fb0设备中的屏幕数据并将其转换为bmp格式图片的过程。适用于Android2.2和4.0模拟器。
工程源码：http://download.youkuaiyun.com/detail/victoryckl/4074654
一个增强版本源码：通过对fb0的操作，实现截屏，和送图片到fb0，支持rgb565 rgb888 xrgb8888格式的bmp和fb0
android上用C语言读取fb0实现截屏，保存为bmp图片，
支持16位(rgb565)、24位(rbg888)两种格式数据，并在android2.2和4.0模拟器上验证通过。
截屏实现主要有两个方面的工作，读取屏幕数据和生成图片。
1.读取屏幕数据
只读方式打开显存设备 /dev/graphics/fb0，再通过mmap用共享方式(MAP_SHARED)映射到一片内存中，其他地方就可以直接以内存的方式读取屏幕数据了。
要注意的是，fb0的虚拟显示设备尺寸，大于实际屏幕显示设备的尺寸，mmap映射时需将安装虚拟尺寸进行映射，否则，截屏可能失败。
针对显存设备的主要代码：
- /********************************************************************
- created: 2012/02/07
- filename: myfb.c
- author:
- purpose:
- *********************************************************************/
- #ifndef WIN32
- //-------------------------------------------------------------------
- #include <stdio.h>
- #include <stdlib.h>
- #include <unistd.h>
- #include <fcntl.h>
- #include <sys/mman.h>
- #include <sys/stat.h>
- #include <sys/types.h>
- #include <linux/fb.h>
- #include <linux/kd.h>
- struct FB {
- unsigned short *bits;
- unsigned size;
- int fd;
- struct fb_fix_screeninfo fi;
- struct fb_var_screeninfo vi;
- };
- int fb_bpp(struct FB *fb)
- {
- if (fb) {
- return fb->vi.bits_per_pixel;
- }
- return 0;
- }
- int fb_width(struct FB *fb)
- {
- if (fb) {
- return fb->vi.xres;
- }
- return 0;
- }
- int fb_height(struct FB *fb)
- {
- if (fb) {
- return fb->vi.yres;
- }
- return 0;
- }
- int fb_size(struct FB *fb)
- {
- if (fb) {
- unsigned bytespp = fb->vi.bits_per_pixel / 8;
- return (fb->vi.xres * fb->vi.yres * bytespp);
- }
- return 0;
- }
- int fb_virtual_size(struct FB *fb)
- {
- if (fb) {
- unsigned bytespp = fb->vi.bits_per_pixel / 8;
- return (fb->vi.xres_virtual * fb->vi.yres_virtual * bytespp);
- }
- return 0;
- }
- void * fb_bits(struct FB *fb)
- {
- unsigned short * bits = NULL;
- if (fb) {
- int offset, bytespp;
- bytespp = fb->vi.bits_per_pixel / 8;
- /* HACK: for several of our 3d cores a specific alignment
- * is required so the start of the fb may not be an integer number of lines
- * from the base. As a result we are storing the additional offset in
- * xoffset. This is not the correct usage for xoffset, it should be added
- * to each line, not just once at the beginning */
- offset = fb->vi.xoffset * bytespp;
- offset += fb->vi.xres * fb->vi.yoffset * bytespp;
- bits = fb->bits + offset / sizeof(*fb->bits);
- }
- return bits;
- }
- void fb_update(struct FB *fb)
- {
- if (fb) {
- fb->vi.yoffset = 1;
- ioctl(fb->fd, FBIOPUT_VSCREENINFO, &fb->vi);
- fb->vi.yoffset = 0;
- ioctl(fb->fd, FBIOPUT_VSCREENINFO, &fb->vi);
- }
- }
- static int fb_open(struct FB *fb)
- {
- if (NULL == fb) {
- return -1;
- }
- fb->fd = open("/dev/graphics/fb0", O_RDONLY);
- if (fb->fd < 0) {
- printf("open(\"/dev/graphics/fb0\") failed!\n");
- return -1;
- }
- if (ioctl(fb->fd, FBIOGET_FSCREENINFO, &fb->fi) < 0) {
- printf("FBIOGET_FSCREENINFO failed!\n");
- goto fail;
- }
- if (ioctl(fb->fd, FBIOGET_VSCREENINFO, &fb->vi) < 0) {
- printf("FBIOGET_VSCREENINFO failed!\n");
- goto fail;
- }
- fb->bits = mmap(0, fb_virtual_size(fb), PROT_READ, MAP_SHARED, fb->fd, 0);
- if (fb->bits == MAP_FAILED) {
- printf("mmap() failed!\n");
- goto fail;
- }
- return 0;
- fail:
- close(fb->fd);
- return -1;
- }
- static void fb_close(struct FB *fb)
- {
- if (fb) {
- munmap(fb->bits, fb_virtual_size(fb));
- close(fb->fd);
- }
- }
- static struct FB g_fb;
- struct FB * fb_create(void)
- {
- memset(&g_fb, 0, sizeof(struct FB));
- if (fb_open(&g_fb)) {
- return NULL;
- }
- return &g_fb;
- }
- void fb_destory(struct FB *fb)
- {
- fb_close(fb);
- }
- //-------------------------------------------------------------------
- #endif//#ifndef WIN32
/********************************************************************
created: 2012/02/07
filename: myfb.c
author:
purpose:
*********************************************************************/
#ifndef WIN32
//-------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <linux/fb.h>
#include <linux/kd.h>
struct FB {
unsigned short *bits;
unsigned size;
int fd;
struct fb_fix_screeninfo fi;
struct fb_var_screeninfo vi;
};
int fb_bpp(struct FB *fb)
{
if (fb) {
return fb->vi.bits_per_pixel;
}
return 0;
}
int fb_width(struct FB *fb)
{
if (fb) {
return fb->vi.xres;
}
return 0;
}
int fb_height(struct FB *fb)
{
if (fb) {
return fb->vi.yres;
}
return 0;
}
int fb_size(struct FB *fb)
{
if (fb) {
unsigned bytespp = fb->vi.bits_per_pixel / 8;
return (fb->vi.xres * fb->vi.yres * bytespp);
}
return 0;
}
int fb_virtual_size(struct FB *fb)
{
if (fb) {
unsigned bytespp = fb->vi.bits_per_pixel / 8;
return (fb->vi.xres_virtual * fb->vi.yres_virtual * bytespp);
}
return 0;
}
void * fb_bits(struct FB *fb)
{
unsigned short * bits = NULL;
if (fb) {
int offset, bytespp;
bytespp = fb->vi.bits_per_pixel / 8;
/* HACK: for several of our 3d cores a specific alignment
* is required so the start of the fb may not be an integer number of lines
* from the base. As a result we are storing the additional offset in
* xoffset. This is not the correct usage for xoffset, it should be added
* to each line, not just once at the beginning */
offset = fb->vi.xoffset * bytespp;
offset += fb->vi.xres * fb->vi.yoffset * bytespp;
bits = fb->bits + offset / sizeof(*fb->bits);
}
return bits;
}
void fb_update(struct FB *fb)
{
if (fb) {
fb->vi.yoffset = 1;
ioctl(fb->fd, FBIOPUT_VSCREENINFO, &fb->vi);
fb->vi.yoffset = 0;
ioctl(fb->fd, FBIOPUT_VSCREENINFO, &fb->vi);
}
}
static int fb_open(struct FB *fb)
{
if (NULL == fb) {
return -1;
}
fb->fd = open("/dev/graphics/fb0", O_RDONLY);
if (fb->fd < 0) {
printf("open(\"/dev/graphics/fb0\") failed!\n");
return -1;
}
if (ioctl(fb->fd, FBIOGET_FSCREENINFO, &fb->fi) < 0) {
printf("FBIOGET_FSCREENINFO failed!\n");
goto fail;
}
if (ioctl(fb->fd, FBIOGET_VSCREENINFO, &fb->vi) < 0) {
printf("FBIOGET_VSCREENINFO failed!\n");
goto fail;
}
fb->bits = mmap(0, fb_virtual_size(fb), PROT_READ, MAP_SHARED, fb->fd, 0);
if (fb->bits == MAP_FAILED) {
printf("mmap() failed!\n");
goto fail;
}
return 0;
fail:
close(fb->fd);
return -1;
}
static void fb_close(struct FB *fb)
{
if (fb) {
munmap(fb->bits, fb_virtual_size(fb));
close(fb->fd);
}
}
static struct FB g_fb;
struct FB * fb_create(void)
{
memset(&g_fb, 0, sizeof(struct FB));
if (fb_open(&g_fb)) {
return NULL;
}
return &g_fb;
}
void fb_destory(struct FB *fb)
{
fb_close(fb);
}
//-------------------------------------------------------------------
#endif//#ifndef WIN322.生成图片
这里生成的图片是bmp格式的，可以根据设备像素的位数自动生成16位(rgb565)、24位(rbg888)两种图片。
主要工作是要正确填充bmp的文件头信息，24位(rbg888)较简单。
16位(rgb565)复杂一点，biCompression成员的值必须是BI_BITFIELDS，原来调色板的前三个位置被三个DWORD变量占据，称为红、绿、蓝掩码，在565格式下，它们则分别为：0xF800、0x07E0、0x001F。
另外，需要主要的是windows要求文件大小必须是4的倍数，文件大小需要做下面的处理才能正确显示。
- head->bfSize = head->bfOffBits + size;
- head->bfSize = (head->bfSize + 3) & ~3;
- size = head->bfSize - head->bfOffBits;
head->bfSize = head->bfOffBits + size;
head->bfSize = (head->bfSize + 3) & ~3;
size = head->bfSize - head->bfOffBits;生成图片的主要代码：
- /********************************************************************
- created: 2012/02/07
- filename: savebmp.c
- author:
- purpose:
- *********************************************************************/
- #include <stdlib.h>
- #include <stdio.h>
- #include <memory.h>
- //-------------------------------------------------------------------
- /*
- 位图文件的组成
- 结构名称 符 号
- 位图文件头 (bitmap-file header) BITMAPFILEHEADER bmfh
- 位图信息头 (bitmap-information header) BITMAPINFOHEADER bmih
- 彩色表 (color table) RGBQUAD aColors[]
- 图象数据阵列字节 BYTE aBitmapBits[]
- */
- typedef struct bmp_header
- {
- short twobyte ;//两个字节，用来保证下面成员紧凑排列，这两个字符不能写到文件中
- //14B
- char bfType[2] ;//!文件的类型,该值必需是0x4D42，也就是字符'BM'
- unsigned int bfSize ;//!说明文件的大小，用字节为单位
- unsigned int bfReserved1;//保留，必须设置为0
- unsigned int bfOffBits ;//!说明从文件头开始到实际的图象数据之间的字节的偏移量，这里为14B+sizeof(BMPINFO)
- }BMPHEADER;
- typedef struct bmp_info
- {
- //40B
- unsigned int biSize ;//!BMPINFO结构所需要的字数
- int biWidth ;//!图象的宽度，以象素为单位
- int biHeight ;//!图象的宽度，以象素为单位,如果该值是正数，说明图像是倒向的，如果该值是负数，则是正向的
- unsigned short biPlanes ;//!目标设备说明位面数，其值将总是被设为1
- unsigned short biBitCount ;//!比特数/象素，其值为1、4、8、16、24、或32
- unsigned int biCompression ;//说明图象数据压缩的类型
- #define BI_RGB 0L //没有压缩
- #define BI_RLE8 1L //每个象素8比特的RLE压缩编码，压缩格式由2字节组成（重复象素计数和颜色索引）；
- #define BI_RLE4 2L //每个象素4比特的RLE压缩编码，压缩格式由2字节组成
- #define BI_BITFIELDS 3L //每个象素的比特由指定的掩码决定。
- unsigned int biSizeImage ;//图象的大小，以字节为单位。当用BI_RGB格式时，可设置为0
- int biXPelsPerMeter ;//水平分辨率，用象素/米表示
- int biYPelsPerMeter ;//垂直分辨率，用象素/米表示
- unsigned int biClrUsed ;//位图实际使用的彩色表中的颜色索引数（设为0的话，则说明使用所有调色板项）
- unsigned int biClrImportant ;//对图象显示有重要影响的颜色索引的数目，如果是0，表示都重要。
- }BMPINFO;
- typedef struct tagRGBQUAD {
- unsigned char rgbBlue;
- unsigned char rgbGreen;
- unsigned char rgbRed;
- unsigned char rgbReserved;
- } RGBQUAD;
- typedef struct tagBITMAPINFO {
- BMPINFO bmiHeader;
- //RGBQUAD bmiColors[1];
- unsigned int rgb[3];
- } BITMAPINFO;
- static int get_rgb888_header(int w, int h, BMPHEADER * head, BMPINFO * info)
- {
- int size = 0;
- if (head && info) {
- size = w * h * 3;
- memset(head, 0, sizeof(* head));
- memset(info, 0, sizeof(* info));
- head->bfType[0] = 'B';
- head->bfType[1] = 'M';
- head->bfOffBits = 14 + sizeof(* info);
- head->bfSize = head->bfOffBits + size;
- head->bfSize = (head->bfSize + 3) & ~3;//windows要求文件大小必须是4的倍数
- size = head->bfSize - head->bfOffBits;
- info->biSize = sizeof(BMPINFO);
- info->biWidth = w;
- info->biHeight = -h;
- info->biPlanes = 1;
- info->biBitCount = 24;
- info->biCompression = BI_RGB;
- info->biSizeImage = size;
- printf("rgb888:%dbit,%d*%d,%d\n", info->biBitCount, w, h, head->bfSize);
- }
- return size;
- }
- static int get_rgb565_header(int w, int h, BMPHEADER * head, BITMAPINFO * info)
- {
- int size = 0;
- if (head && info) {
- size = w * h * 2;
- memset(head, 0, sizeof(* head));
- memset(info, 0, sizeof(* info));
- head->bfType[0] = 'B';
- head->bfType[1] = 'M';
- head->bfOffBits = 14 + sizeof(* info);
- head->bfSize = head->bfOffBits + size;
- head->bfSize = (head->bfSize + 3) & ~3;
- size = head->bfSize - head->bfOffBits;
- info->bmiHeader.biSize = sizeof(info->bmiHeader);
- info->bmiHeader.biWidth = w;
- info->bmiHeader.biHeight = -h;
- info->bmiHeader.biPlanes = 1;
- info->bmiHeader.biBitCount = 16;
- info->bmiHeader.biCompression = BI_BITFIELDS;
- info->bmiHeader.biSizeImage = size;
- info->rgb[0] = 0xF800;
- info->rgb[1] = 0x07E0;
- info->rgb[2] = 0x001F;
- printf("rgb565:%dbit,%d*%d,%d\n", info->bmiHeader.biBitCount, w, h, head->bfSize);
- }
- return size;
- }
- static int save_bmp_rgb565(FILE * hfile, int w, int h, void * pdata)
- {
- int success = 0;
- int size = 0;
- BMPHEADER head;
- BITMAPINFO info;
- size = get_rgb565_header(w, h, &head, &info);
- if (size > 0) {
- fwrite(head.bfType, 1, 14, hfile);
- fwrite(&info, 1, sizeof(info), hfile);
- fwrite(pdata, 1, size, hfile);
- success = 1;
- }
- return success;
- }
- static int save_bmp_rgb888(FILE * hfile, int w, int h, void * pdata)
- {
- int success = 0;
- int size = 0;
- BMPHEADER head;
- BMPINFO info;
- size = get_rgb888_header(w, h, &head, &info);
- if (size > 0) {
- fwrite(head.bfType, 1, 14, hfile);
- fwrite(&info, 1, sizeof(info), hfile);
- fwrite(pdata, 1, size, hfile);
- success = 1;
- }
- return success;
- }
- int save_bmp(const char * path, int w, int h, void * pdata, int bpp)
- {
- int success = 0;
- FILE * hfile = NULL;
- do
- {
- if (path == NULL || w <= 0 || h <= 0 || pdata == NULL) {
- printf("if (path == NULL || w <= 0 || h <= 0 || pdata == NULL)\n");
- break;
- }
- remove(path);
- hfile = fopen(path, "wb");
- if (hfile == NULL) {
- printf("open(%s) failed!\n", path);
- break;
- }
- switch (bpp)
- {
- case 16:
- success = save_bmp_rgb565(hfile, w, h, pdata);
- break;
- case 24:
- success = save_bmp_rgb888(hfile, w, h, pdata);
- break;
- default:
- printf("error: not support format!\n");
- success = 0;
- break;
- }
- } while (0);
- if (hfile != NULL)
- fclose(hfile);
- return success;
- }
- //-------------------------------------------------------------------
/********************************************************************
created: 2012/02/07
filename: savebmp.c
author:
purpose:
*********************************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <memory.h>
//-------------------------------------------------------------------
/*
位图文件的组成
结构名称 符 号
位图文件头 (bitmap-file header) BITMAPFILEHEADER bmfh
位图信息头 (bitmap-information header) BITMAPINFOHEADER bmih
彩色表 (color table) RGBQUAD aColors[]
图象数据阵列字节 BYTE aBitmapBits[]
*/
typedef struct bmp_header
{
short twobyte ;//两个字节，用来保证下面成员紧凑排列，这两个字符不能写到文件中
//14B
char bfType[2] ;//!文件的类型,该值必需是0x4D42，也就是字符'BM'
unsigned int bfSize ;//!说明文件的大小，用字节为单位
unsigned int bfReserved1;//保留，必须设置为0
unsigned int bfOffBits ;//!说明从文件头开始到实际的图象数据之间的字节的偏移量，这里为14B+sizeof(BMPINFO)
}BMPHEADER;
typedef struct bmp_info
{
//40B
unsigned int biSize ;//!BMPINFO结构所需要的字数
int biWidth ;//!图象的宽度，以象素为单位
int biHeight ;//!图象的宽度，以象素为单位,如果该值是正数，说明图像是倒向的，如果该值是负数，则是正向的
unsigned short biPlanes ;//!目标设备说明位面数，其值将总是被设为1
unsigned short biBitCount ;//!比特数/象素，其值为1、4、8、16、24、或32
unsigned int biCompression ;//说明图象数据压缩的类型
#define BI_RGB 0L //没有压缩
#define BI_RLE8 1L //每个象素8比特的RLE压缩编码，压缩格式由2字节组成（重复象素计数和颜色索引）；
#define BI_RLE4 2L //每个象素4比特的RLE压缩编码，压缩格式由2字节组成
#define BI_BITFIELDS 3L //每个象素的比特由指定的掩码决定。
unsigned int biSizeImage ;//图象的大小，以字节为单位。当用BI_RGB格式时，可设置为0
int biXPelsPerMeter ;//水平分辨率，用象素/米表示
int biYPelsPerMeter ;//垂直分辨率，用象素/米表示
unsigned int biClrUsed ;//位图实际使用的彩色表中的颜色索引数（设为0的话，则说明使用所有调色板项）
unsigned int biClrImportant ;//对图象显示有重要影响的颜色索引的数目，如果是0，表示都重要。
}BMPINFO;
typedef struct tagRGBQUAD {
unsigned char rgbBlue;
unsigned char rgbGreen;
unsigned char rgbRed;
unsigned char rgbReserved;
} RGBQUAD;
typedef struct tagBITMAPINFO {
BMPINFO bmiHeader;
//RGBQUAD bmiColors[1];
unsigned int rgb[3];
} BITMAPINFO;
static int get_rgb888_header(int w, int h, BMPHEADER * head, BMPINFO * info)
{
int size = 0;
if (head && info) {
size = w * h * 3;
memset(head, 0, sizeof(* head));
memset(info, 0, sizeof(* info));
head->bfType[0] = 'B';
head->bfType[1] = 'M';
head->bfOffBits = 14 + sizeof(* info);
head->bfSize = head->bfOffBits + size;
head->bfSize = (head->bfSize + 3) & ~3;//windows要求文件大小必须是4的倍数
size = head->bfSize - head->bfOffBits;
info->biSize = sizeof(BMPINFO);
info->biWidth = w;
info->biHeight = -h;
info->biPlanes = 1;
info->biBitCount = 24;
info->biCompression = BI_RGB;
info->biSizeImage = size;
printf("rgb888:%dbit,%d*%d,%d\n", info->biBitCount, w, h, head->bfSize);
}
return size;
}
static int get_rgb565_header(int w, int h, BMPHEADER * head, BITMAPINFO * info)
{
int size = 0;
if (head && info) {
size = w * h * 2;
memset(head, 0, sizeof(* head));
memset(info, 0, sizeof(* info));
head->bfType[0] = 'B';
head->bfType[1] = 'M';
head->bfOffBits = 14 + sizeof(* info);
head->bfSize = head->bfOffBits + size;
head->bfSize = (head->bfSize + 3) & ~3;
size = head->bfSize - head->bfOffBits;
info->bmiHeader.biSize = sizeof(info->bmiHeader);
info->bmiHeader.biWidth = w;
info->bmiHeader.biHeight = -h;
info->bmiHeader.biPlanes = 1;
info->bmiHeader.biBitCount = 16;
info->bmiHeader.biCompression = BI_BITFIELDS;
info->bmiHeader.biSizeImage = size;
info->rgb[0] = 0xF800;
info->rgb[1] = 0x07E0;
info->rgb[2] = 0x001F;
printf("rgb565:%dbit,%d*%d,%d\n", info->bmiHeader.biBitCount, w, h, head->bfSize);
}
return size;
}
static int save_bmp_rgb565(FILE * hfile, int w, int h, void * pdata)
{
int success = 0;
int size = 0;
BMPHEADER head;
BITMAPINFO info;
size = get_rgb565_header(w, h, &head, &info);
if (size > 0) {
fwrite(head.bfType, 1, 14, hfile);
fwrite(&info, 1, sizeof(info), hfile);
fwrite(pdata, 1, size, hfile);
success = 1;
}
return success;
}
static int save_bmp_rgb888(FILE * hfile, int w, int h, void * pdata)
{
int success = 0;
int size = 0;
BMPHEADER head;
BMPINFO info;
size = get_rgb888_header(w, h, &head, &info);
if (size > 0) {
fwrite(head.bfType, 1, 14, hfile);
fwrite(&info, 1, sizeof(info), hfile);
fwrite(pdata, 1, size, hfile);
success = 1;
}
return success;
}
int save_bmp(const char * path, int w, int h, void * pdata, int bpp)
{
int success = 0;
FILE * hfile = NULL;
do
{
if (path == NULL || w <= 0 || h <= 0 || pdata == NULL) {
printf("if (path == NULL || w <= 0 || h <= 0 || pdata == NULL)\n");
break;
}
remove(path);
hfile = fopen(path, "wb");
if (hfile == NULL) {
printf("open(%s) failed!\n", path);
break;
}
switch (bpp)
{
case 16:
success = save_bmp_rgb565(hfile, w, h, pdata);
break;
case 24:
success = save_bmp_rgb888(hfile, w, h, pdata);
break;
default:
printf("error: not support format!\n");
success = 0;
break;
}
} while (0);
if (hfile != NULL)
fclose(hfile);
return success;
}
//-------------------------------------------------------------------
3.运行方式：
cygwin下用ndk编译成可执行文件，再将生成的可执行文件push到模拟器的/data/local路径，
修改文件为可执行的，直接运行便可以截屏，图片保存到/mnt/sdcard/s.bmp。
- Administrator@xxx /cygdrive/e
- $ cd myprj/screenshot/jni/
- Administrator@xxx /cygdrive/e/myprj/screenshot/jni
- $ ndk-build
- Compile thumb : savebmp <= savebmp.c
- Compile thumb : savebmp <= screenshot.c
- StaticLibrary : libsavebmp.a
- Executable : save
- Install : save => libs/armeabi/save
- Administrator@xxx /cygdrive/e/myprj/screenshot/jni
- $ adb shell
- error: device offline
- Administrator@xxx /cygdrive/e/myprj/screenshot/jni
- $ adb shell
- #
- Administrator@xxx /cygdrive/e/myprj/screenshot/jni
- $ adb push ../libs/armeabi/save /data/local
- 83 KB/s (10636 bytes in 0.125s)
- Administrator@xxx /cygdrive/e/myprj/screenshot/jni
- $ adb shell
- # cd /data/local
- cd /data/local
- # chmod 777 save
- chmod 777 save
- # ./save
- ./save
- rgb565:16bit,800*480,768068
- # ls -l /mnt/sdcard
- ls -l /mnt/sdcard
- d---rwxr-x system sdcard_rw 2012-02-19 12:39 LOST.DIR
- d---rwxr-x system sdcard_rw 2012-02-20 13:22 DCIM
- ----rwxr-x system sdcard_rw 768068 2012-02-20 13:22 s.bmp
- #
Administrator@xxx /cygdrive/e
$ cd myprj/screenshot/jni/
Administrator@xxx /cygdrive/e/myprj/screenshot/jni
$ ndk-build
Compile thumb : savebmp <= savebmp.c
Compile thumb : savebmp <= screenshot.c
StaticLibrary : libsavebmp.a
Executable : save
Install : save => libs/armeabi/save
Administrator@xxx /cygdrive/e/myprj/screenshot/jni
$ adb shell
error: device offline
Administrator@xxx /cygdrive/e/myprj/screenshot/jni
$ adb shell
#
Administrator@xxx /cygdrive/e/myprj/screenshot/jni
$ adb push ../libs/armeabi/save /data/local
83 KB/s (10636 bytes in 0.125s)
Administrator@xxx /cygdrive/e/myprj/screenshot/jni
$ adb shell
# cd /data/local
cd /data/local
# chmod 777 save
chmod 777 save
# ./save
./save
rgb565:16bit,800*480,768068
# ls -l /mnt/sdcard
ls -l /mnt/sdcard
d---rwxr-x system sdcard_rw 2012-02-19 12:39 LOST.DIR
d---rwxr-x system sdcard_rw 2012-02-20 13:22 DCIM
----rwxr-x system sdcard_rw 768068 2012-02-20 13:22 s.bmp
#PS：工程源码中的VC工程主要用来调试生成图片的功能。
=====================================================================================================
目前，在增强版本中添加了32位的支持，但是没有32位的设备进行测试，已经有几位网友测试过，32位截图会出现颜色偏差和位置偏移，目前我这里还没有办法调试，所以32位截图的问题我还没有解决。
有位网友在小米手机上测试过也是有色差和错位问题，但后来直接在java中用Runtime.exec("/system/bin/screencap -p path")来截屏，还是png格式的。不是每个设备上都有screencap。
关于fb0中像素的格式可以参考
android4.0p-ics-src/system/core/adb# vi framebuffer_service.c，里面列举了五种格式，不过有些设备上可能不是下面的任何一种。
- case 1: /* RGBA_8888 */
- fbinfo.bpp = 32;
- fbinfo.size = w * h * 4;
- fbinfo.width = w;
- fbinfo.height = h;
- fbinfo.red_offset = 0;
- fbinfo.red_length = 8;
- fbinfo.green_offset = 8;
- fbinfo.green_length = 8;
- fbinfo.blue_offset = 16;
- fbinfo.blue_length = 8;
- fbinfo.alpha_offset = 24;
- fbinfo.alpha_length = 8;
- break;
- case 2: /* RGBX_8888 */
- fbinfo.bpp = 32;
- fbinfo.size = w * h * 4;
- fbinfo.width = w;
- fbinfo.height = h;
- fbinfo.red_offset = 0;
- fbinfo.red_length = 8;
- fbinfo.green_offset = 8;
- fbinfo.green_length = 8;
- fbinfo.blue_offset = 16;
- fbinfo.blue_length = 8;
- fbinfo.alpha_offset = 24;
- fbinfo.alpha_length = 0;
- break;
- case 3: /* RGB_888 */
- fbinfo.bpp = 24;
- fbinfo.size = w * h * 3;
- fbinfo.width = w;
- fbinfo.height = h;
- fbinfo.red_offset = 0;
- fbinfo.red_length = 8;
- fbinfo.green_offset = 8;
- fbinfo.green_length = 8;
- fbinfo.blue_offset = 16;
- fbinfo.blue_length = 8;
- fbinfo.alpha_offset = 24;
- fbinfo.alpha_length = 0;
- break;
- case 4: /* RGB_565 */
- fbinfo.bpp = 16;
- fbinfo.size = w * h * 2;
- fbinfo.width = w;
- fbinfo.height = h;
- fbinfo.red_offset = 11;
- fbinfo.red_length = 5;
- fbinfo.green_offset = 5;
- fbinfo.green_length = 6;
- fbinfo.blue_offset = 0;
- fbinfo.blue_length = 5;
- fbinfo.alpha_offset = 0;
- fbinfo.alpha_length = 0;
- break;
- case 5: /* BGRA_8888 */
- fbinfo.bpp = 32;
- fbinfo.size = w * h * 4;
- fbinfo.width = w;
- fbinfo.height = h;
- fbinfo.red_offset = 16;
- fbinfo.red_length = 8;
- fbinfo.green_offset = 8;
- fbinfo.green_length = 8;
- fbinfo.blue_offset = 0;
- fbinfo.blue_length = 8;
- fbinfo.alpha_offset = 24;
- fbinfo.alpha_length = 8;
- break;
case 1: /* RGBA_8888 */
fbinfo.bpp = 32;
fbinfo.size = w * h * 4;
fbinfo.width = w;
fbinfo.height = h;
fbinfo.red_offset = 0;
fbinfo.red_length = 8;
fbinfo.green_offset = 8;
fbinfo.green_length = 8;
fbinfo.blue_offset = 16;
fbinfo.blue_length = 8;
fbinfo.alpha_offset = 24;
fbinfo.alpha_length = 8;
break;
case 2: /* RGBX_8888 */
fbinfo.bpp = 32;
fbinfo.size = w * h * 4;
fbinfo.width = w;
fbinfo.height = h;
fbinfo.red_offset = 0;
fbinfo.red_length = 8;
fbinfo.green_offset = 8;
fbinfo.green_length = 8;
fbinfo.blue_offset = 16;
fbinfo.blue_length = 8;
fbinfo.alpha_offset = 24;
fbinfo.alpha_length = 0;
break;
case 3: /* RGB_888 */
fbinfo.bpp = 24;
fbinfo.size = w * h * 3;
fbinfo.width = w;
fbinfo.height = h;
fbinfo.red_offset = 0;
fbinfo.red_length = 8;
fbinfo.green_offset = 8;
fbinfo.green_length = 8;
fbinfo.blue_offset = 16;
fbinfo.blue_length = 8;
fbinfo.alpha_offset = 24;
fbinfo.alpha_length = 0;
break;
case 4: /* RGB_565 */
fbinfo.bpp = 16;
fbinfo.size = w * h * 2;
fbinfo.width = w;
fbinfo.height = h;
fbinfo.red_offset = 11;
fbinfo.red_length = 5;
fbinfo.green_offset = 5;
fbinfo.green_length = 6;
fbinfo.blue_offset = 0;
fbinfo.blue_length = 5;
fbinfo.alpha_offset = 0;
fbinfo.alpha_length = 0;
break;
case 5: /* BGRA_8888 */
fbinfo.bpp = 32;
fbinfo.size = w * h * 4;
fbinfo.width = w;
fbinfo.height = h;
fbinfo.red_offset = 16;
fbinfo.red_length = 8;
fbinfo.green_offset = 8;
fbinfo.green_length = 8;
fbinfo.blue_offset = 0;
fbinfo.blue_length = 8;
fbinfo.alpha_offset = 24;
fbinfo.alpha_length = 8;
break;另外，关于截屏在android4.0的源码用有两个程序可以参考，这两个程序都可以截屏，一个是c++实现的，另一个是c的。
ics-src\frameworks\base\cmds\screencap\screencap.cpp
ics-src\frameworks\base\cmds\screenshot\screenshot.c
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