Linux下C语言实现LCD屏幕截图

来源：互联网发布：数据库删除表语句编辑：程序博客网时间：2024/04/30 14:18

一、概述

最近看到网上有人问怎么用C语言实现屏幕截图，刚好自己也在研究Linux驱动，于是花了半天时间把Linux的FrameBuffer驱动看懂了个七八，接着就动手写了个LCD屏幕截图的应用程序。

一些说明：

1. 板子LCD的分辨率为480x272，像素格式为RGB565。

2. 程序首先获取LCD的一些参数，然后将获取到的一帧数据转换为RGB24格式，最后用jpeglib库压缩为jpg格式的图片。

　 3. 在嵌入式Linux的板子上测试通过。

二、实现

程序中有注释，不多说，直接上程序：

  1 #include<stdio.h>  2 #include<stdlib.h>  3 #include<sys/ioctl.h>  4 #include<unistd.h>  5 #include<fcntl.h>  6 #include <malloc.h>  7   8 #include<linux/fb.h>  9  10 #include <jpeglib.h> 11 #include <jerror.h> 12  13  14 /*RGB565转RGB24函数 15 *@rgb565: 指向存放rgb565数据的起始地址 16 *@rgb24：指向存放rgb24数据的起始地址 17 *@width：屏幕（分辨率）的宽度 18 *@height：屏幕（分辨率）的高度 19 */ 20 int RGB565_to_RGB24(unsigned char *rgb565,unsigned char *rgb24,int width,int height) 21 { 22     int i; 23     int whole = width*height; 24     unsigned char r,g,b; 25     unsigned short int *pix565; 26      27     pix565 = (unsigned short int *)rgb565; 28  29     for(i = 0;i < whole;i++) 30     {     31         r = ((*pix565)>>11)&0x1f; 32         *rgb24 = (r<<3) | (r>>2); 33         rgb24++; 34         g = ((*pix565)>>5)&0x3f; 35         *rgb24 = (g<<2) | (g>>4); 36         rgb24++; 37         b = (*pix565)&0x1f; 38         *rgb24 = (b<<3) | (b>>2); 39         rgb24++; 40         pix565++;     41              42     } 43     return 1; 44 } 45  46 /*jpeg压缩函数 47 *@rgb：指向存放rgb24数据的起始地址 48 *@width：屏幕（分辨率）的宽度 49 *@height：屏幕（分辨率）的高度 50 */ 51 int jpeg_compress(unsigned char *rgb,int width,int height) 52 { 53         struct jpeg_compress_struct cinfo; 54         struct jpeg_error_mgr jerr; 55         FILE * outfile; 56         JSAMPROW row_pointer[1]; 57         int row_stride; 58         cinfo.err = jpeg_std_error(&jerr); 59         jpeg_create_compress(&cinfo); 60         //输出文件名为：out.jpg 61         if ((outfile = fopen("out.jpg", "wb")) == NULL) 62         { 63             printf("can not open out.jpg\n"); 64             return -1; 65         } 66         jpeg_stdio_dest(&cinfo, outfile); 67  68         cinfo.image_width = width; 69         cinfo.image_height = height; 70         cinfo.input_components = 3; 71         //输入数据格式为RGB 72         cinfo.in_color_space = JCS_RGB; 73  74         jpeg_set_defaults(&cinfo); 75         //压缩质量为80 76         jpeg_set_quality(&cinfo, 80, TRUE ); 77         jpeg_start_compress(&cinfo, TRUE); 78         row_stride = width * 3; 79  80         while (cinfo.next_scanline < cinfo.image_height) 81         { 82             row_pointer[0] = &rgb[cinfo.next_scanline * row_stride]; 83             (void) jpeg_write_scanlines(&cinfo, row_pointer, 1); 84         } 85  86         jpeg_finish_compress(&cinfo); 87         fclose(outfile); 88  89         jpeg_destroy_compress(&cinfo); 90  91         return 1; 92 } 93  94  95 int main() 96 { 97  98     int fd; 99     struct fb_var_screeninfo fb_var_info;100     struct fb_fix_screeninfo fb_fix_info;101     unsigned char *trgb;102     unsigned char *rgb;103     int buffer_size;104 105     //打开framebuffer设备106     fd = open("/dev/fb0",O_RDONLY);107     if(fd < 0)108     {109         printf("can not open dev\n");110         exit(1);111     }112 113     //获取LCD的可变参数114     ioctl(fd,FBIOGET_VSCREENINFO,&fb_var_info);115     //一个像素多少位    116     printf("bits_per_pixel: %d\n",fb_var_info.bits_per_pixel);117     //x分辨率118     printf("xres: %d\n",fb_var_info.xres);119     //y分辨率120     printf("yres: %d\n",fb_var_info.yres);121     //r分量长度（bit）122     printf("red_length: %d\n",fb_var_info.red.length);123     //g分量长度（bit）124     printf("green_length: %d\n",fb_var_info.green.length);125     //b分量长度（bit）126     printf("blue_length: %d\n",fb_var_info.blue.length);127     //t(透明度)分量长度（bit）128     printf("transp_length: %d\n",fb_var_info.transp.length);129     //r分量偏移130     printf("red_offset: %d\n",fb_var_info.red.offset);131     //g分量偏移132     printf("green_offset: %d\n",fb_var_info.green.offset);133     //b分量偏移134     printf("blue_offset: %d\n",fb_var_info.blue.offset);135     //t分量偏移136     printf("transp_offset: %d\n",fb_var_info.transp.offset);137 138     //获取LCD的固定参数139     ioctl(fd,FBIOGET_FSCREENINFO,&fb_fix_info);140     //一帧大小141     printf("smem_len: %d\n",fb_fix_info.smem_len);142     //一行大小143     printf("line_length: %d\n",fb_fix_info.line_length);144 145     //一帧大小146     buffer_size = (fb_var_info.xres * fb_var_info.yres * fb_var_info.bits_per_pixel/8);147 148     trgb = (unsigned char *)malloc(buffer_size);149     if(trgb==NULL)150         exit(0);151     rgb = (unsigned char *)malloc(fb_var_info.xres * fb_var_info.yres * 3);152     if(rgb==NULL)153     {154         goto here;155     }156     //获取一帧数据157     if(read(fd,trgb,buffer_size) < 0)158     {159         printf("reaf failed!\n");160         goto read_fail;161     }162     //格式转换163     RGB565_to_RGB24(trgb,rgb,fb_var_info.xres,fb_var_info.yres);164     //jpeg压缩165     if(jpeg_compress(rgb,fb_var_info.xres,fb_var_info.yres)<0)166         printf("compress failed!\n");        167     168 read_fail:169     free(rgb);170 here:171     free(trgb);172     173 174     close(fd);175 176     return 0;177 }

效果：