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分类: 嵌入式

2011-05-03 21:00:46

 本文的copyright归yuweixian4230@163.com 所有,使用GPL发布,可以自由拷贝,转载。但转载请保持文档的完整性,注明原作者及原链接,严禁用于任何商业用途。
作者:yuweixian4230@163.com
博客:
yuweixian4230.blog.chinaunix.net 


  使用了 http://blog.csdn.net/yruilin/archive/2009/01/17/3808715.aspx 的程序,对它进行的测试,在自己开发板上可以正常显示 RGB565

将代码贴下:  jpeg1.rar  

编译如下: arm-linux-gcc jpeg1.c -ljpeg -o jpeg1  //需要加上jpeg库

  1. /*

  2.  * $Id: fv.c

  3.  * $Desp: draw jpeg to framebuffer

  4.  * $Author: rockins

  5.  * $Date: Wed Jan 3 20:15:49 CST 2007

  6.  */

  7. #include <stdio.h>

  8. #include <stdlib.h>

  9. #include <fcntl.h>

  10. #include <linux/fb.h>

  11. #include <sys/types.h>

  12. #include <sys/stat.h>

  13. #include <sys/mman.h>

  14. #include <jpeglib.h>

  15. #include <jerror.h>

  16. #define FB_DEV "/dev/fb0"

  17. /***************** function declaration ******************/

  18. void usage(char *msg);

  19. unsigned short RGB888toRGB565(unsigned char red,

  20.                                                     unsigned char green, unsigned char blue);

  21. int fb_open(char *fb_device);

  22. int fb_close(int fd);

  23. int fb_stat(int fd, int *width, int *height, int *depth);

  24. void *fb_mmap(int fd, unsigned int screensize);

  25. int fb_munmap(void *start, size_t length);

  26. int fb_pixel(void *fbmem, int width, int height,

  27.                                            int x, int y, unsigned short color);

  28. /************ function implementation ********************/

  29. int

  30. main(int argc, char *argv[])

  31. {

  32.        /*

  33.         * declaration for jpeg decompression

  34.         */

  35.        struct jpeg_decompress_struct cinfo;

  36.        struct jpeg_error_mgr jerr;

  37.        FILE *infile;

  38.        unsigned char *buffer;

  39.        /*

  40.         * declaration for framebuffer device

  41.         */

  42.        int fbdev;

  43.        char *fb_device;

  44.        unsigned char *fbmem;

  45.        unsigned int screensize;

  46.        unsigned int fb_width;

  47.        unsigned int fb_height;

  48.        unsigned int fb_depth;

  49.        unsigned int x;

  50.        unsigned int y;

  51.        /*

  52.         * check auguments

  53.         */

  54.        if (argc != 2) {

  55.               usage("insuffient auguments");

  56.               exit(-1);

  57.        }

  58.        /*

  59.         * open framebuffer device

  60.         */

  61.        if ((fb_device = getenv("FRAMEBUFFER")) == NULL)

  62.               fb_device = FB_DEV;

  63.        fbdev = fb_open(fb_device);

  64.        /*

  65.         * get status of framebuffer device

  66.         */

  67.        fb_stat(fbdev, &fb_width, &fb_height, &fb_depth);

  68.        /*

  69.         * map framebuffer device to shared memory

  70.         */

  71.        screensize = fb_width * fb_height * fb_depth / 8;

  72.        fbmem = fb_mmap(fbdev, screensize);

  73.        /*

  74.         * open input jpeg file

  75.         */

  76.        if ((infile = fopen(argv[1], "rb")) == NULL) {

  77.               fprintf(stderr, "open %s failed\n", argv[1]);

  78.               exit(-1);

  79.        }

  80.        /*

  81.         * init jpeg decompress object error handler

  82.         */

  83.        cinfo.err = jpeg_std_error(&jerr);

  84.        jpeg_create_decompress(&cinfo);

  85.        /*

  86.         * bind jpeg decompress object to infile

  87.         */

  88.        jpeg_stdio_src(&cinfo, infile);

  89.        /*

  90.         * read jpeg header

  91.         */

  92.        jpeg_read_header(&cinfo, TRUE);

  93.        /*

  94.         * decompress process.

  95.         * note: after jpeg_start_decompress() is called

  96.         * the dimension infomation will be known,

  97.         * so allocate memory buffer for scanline immediately

  98.         */

  99.        jpeg_start_decompress(&cinfo);

  100.        if ((cinfo.output_width > fb_width) ||

  101.               (cinfo.output_height > fb_height)) {

  102.               printf("too large JPEG file,cannot display\n");

  103.               return (-1);

  104.        }

  105.        buffer = (unsigned char *) malloc(cinfo.output_width *

  106.                                                                  cinfo.output_components);

  107.        y = 0;

  108.        while (cinfo.output_scanline < cinfo.output_height) {

  109.               jpeg_read_scanlines(&cinfo, &buffer, 1);

  110.               if (fb_depth == 16) {

  111.                      unsigned short color;

  112.                      for (x = 0; x < cinfo.output_width; x++) {

  113.                             color = RGB888toRGB565(buffer[x * 3],

  114.                                           buffer[x * 3 + 1], buffer[x * 3 + 2]);

  115.                             fb_pixel(fbmem, fb_width, fb_height, x, y, color);

  116.                      }

  117.               } else if (fb_depth == 24) {

  118.                      memcpy((unsigned char *) fbmem + y * fb_width * 3,

  119.                                buffer, cinfo.output_width * cinfo.output_components);

  120.               }

  121.               y++; // next scanline

  122.        }

  123.        /*

  124.         * finish decompress, destroy decompress object

  125.         */

  126.        jpeg_finish_decompress(&cinfo);

  127.        jpeg_destroy_decompress(&cinfo);

  128.        /*

  129.         * release memory buffer

  130.         */

  131.        free(buffer);

  132.        /*

  133.         * close jpeg inputing file

  134.         */

  135.        fclose(infile);

  136.        /*

  137.         * unmap framebuffer's shared memory

  138.         */

  139.        fb_munmap(fbmem, screensize);

  140.        /*

  141.         * close framebuffer device

  142.         */

  143.        fb_close(fbdev);

  144.        return (0);

  145. }

  146. void

  147. usage(char *msg)

  148. {

  149.        fprintf(stderr, "%s\n", msg);

  150.        printf("Usage: fv some-jpeg-file.jpg\n");

  151. }

  152. /*

  153.  * convert 24bit RGB888 to 16bit RGB565 color format

  154.  */

  155. unsigned short

  156. RGB888toRGB565(unsigned char red, unsigned char green, unsigned char blue)

  157. {

  158.        unsigned short B = (blue >> 3) & 0x001F;

  159.        unsigned short G = ((green >> 2) << 5) & 0x07E0;

  160.        unsigned short R = ((red >> 3) << 11) & 0xF800;

  161.        return (unsigned short) (R | G | B);

  162. }

  163. /*

  164.  * open framebuffer device.

  165.  * return positive file descriptor if success,

  166.  * else return -1.

  167.  */

  168. int

  169. fb_open(char *fb_device)

  170. {

  171.        int fd;

  172.        if ((fd = open(fb_device, O_RDWR)) < 0) {

  173.               perror(__func__);

  174.               return (-1);

  175.        }

  176.        return (fd);

  177. }

  178. /*

  179.  * get framebuffer's width,height,and depth.

  180.  * return 0 if success, else return -1.

  181.  */

  182. int

  183. fb_stat(int fd, int *width, int *height, int *depth)

  184. {

  185.        struct fb_fix_screeninfo fb_finfo;

  186.        struct fb_var_screeninfo fb_vinfo;

  187.        if (ioctl(fd, FBIOGET_FSCREENINFO, &fb_finfo)) {

  188.               perror(__func__);

  189.               return (-1);

  190.        }

  191.        if (ioctl(fd, FBIOGET_VSCREENINFO, &fb_vinfo)) {

  192.               perror(__func__);

  193.               return (-1);

  194.        }

  195.        *width = fb_vinfo.xres;

  196.        *height = fb_vinfo.yres;

  197.        *depth = fb_vinfo.bits_per_pixel;

  198.        return (0);

  199. }

  200. /*

  201.  * map shared memory to framebuffer device.

  202.  * return maped memory if success,

  203.  * else return -1, as mmap dose.

  204.  */

  205. void *

  206. fb_mmap(int fd, unsigned int screensize)

  207. {

  208.        caddr_t fbmem;

  209.        if ((fbmem = mmap(0, screensize, PROT_READ | PROT_WRITE,

  210.                                      MAP_SHARED, fd, 0)) == MAP_FAILED) {

  211.               perror(__func__);

  212.               return (void *) (-1);

  213.        }

  214.        return (fbmem);

  215. }

  216. /*

  217.  * unmap map memory for framebuffer device.

  218.  */

  219. int

  220. fb_munmap(void *start, size_t length)

  221. {

  222.        return (munmap(start, length));

  223. }

  224. /*

  225.  * close framebuffer device

  226.  */

  227. int

  228. fb_close(int fd)

  229. {

  230.        return (close(fd));

  231. }

  232. /*

  233.  * display a pixel on the framebuffer device.

  234.  * fbmem is the starting memory of framebuffer,

  235.  * width and height are dimension of framebuffer,

  236.  * x and y are the coordinates to display,

  237.  * color is the pixel's color value.

  238.  * return 0 if success, otherwise return -1.

  239.  */

  240. int

  241. fb_pixel(void *fbmem, int width, int height,

  242.                int x, int y, unsigned short color)

  243. {

  244.        if ((x > width) || (y > height))

  245.               return (-1);

  246.        unsigned short *dst = ((unsigned short *) fbmem + y * width + x);

  247.        *dst = color;

  248.        return (0);

  249. }


在 开发板上运行

   ./jpeg1 2.jpg

然后用截图软件 gsoap test.jpg /dev/fb0  保存数据

发现:原图片 2.jpg 大小才 25 KB
      通过jpeg 解码后,80 KB
在开发LCD上显示很清楚
















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