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使用libjpeg显示JPEG图像在framebuffer 测试（八）

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. /*

  3.  * $Id: fv.c

  5.  * $Desp: draw jpeg to framebuffer

  7.  * $Author: rockins

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

  11.  */

  13. #include <stdio.h>

  15. #include <stdlib.h>

  17. #include <fcntl.h>

  19. #include <linux/fb.h>

  21. #include <sys/types.h>

  23. #include <sys/stat.h>

  25. #include <sys/mman.h>

  27. #include <jpeglib.h>

  29. #include <jerror.h>

  31. #define FB_DEV "/dev/fb0"

  33. /***************** function declaration ******************/

  35. void usage(char *msg);

  37. unsigned short RGB888toRGB565(unsigned char red,

  39.                                                     unsigned char green, unsigned char blue);

  41. int fb_open(char *fb_device);

  43. int fb_close(int fd);

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

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

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

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

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

  55. /************ function implementation ********************/

  57. int

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

  61. {

  63.        /*

  65.         * declaration for jpeg decompression

  67.         */

  69.        struct jpeg_decompress_struct cinfo;

  71.        struct jpeg_error_mgr jerr;

  73.        FILE *infile;

  75.        unsigned char *buffer;

  77.        /*

  79.         * declaration for framebuffer device

  81.         */

  83.        int fbdev;

  85.        char *fb_device;

  87.        unsigned char *fbmem;

  89.        unsigned int screensize;

  91.        unsigned int fb_width;

  93.        unsigned int fb_height;

  95.        unsigned int fb_depth;

  97.        unsigned int x;

  99.        unsigned int y;

  101.        /*

  103.         * check auguments

  105.         */

  107.        if (argc != 2) {

  109.               usage("insuffient auguments");

  111.               exit(-1);

  113.        }

  115.        /*

  117.         * open framebuffer device

  119.         */

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

  123.               fb_device = FB_DEV;

  125.        fbdev = fb_open(fb_device);

  127.        /*

  129.         * get status of framebuffer device

  131.         */

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

  135.        /*

  137.         * map framebuffer device to shared memory

  139.         */

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

  143.        fbmem = fb_mmap(fbdev, screensize);

  145.        /*

  147.         * open input jpeg file

  149.         */

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

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

  155.               exit(-1);

  157.        }

  159.        /*

  161.         * init jpeg decompress object error handler

  163.         */

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

  167.        jpeg_create_decompress(&cinfo);

  169.        /*

  171.         * bind jpeg decompress object to infile

  173.         */

  175.        jpeg_stdio_src(&cinfo, infile);

  177.        /*

  179.         * read jpeg header

  181.         */

  183.        jpeg_read_header(&cinfo, TRUE);

  185.        /*

  187.         * decompress process.

  189.         * note: after jpeg_start_decompress() is called

  191.         * the dimension infomation will be known,

  193.         * so allocate memory buffer for scanline immediately

  195.         */

  197.        jpeg_start_decompress(&cinfo);

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

  201.               (cinfo.output_height > fb_height)) {

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

  205.               return (-1);

  207.        }

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

  211.                                                                  cinfo.output_components);

  213.        y = 0;

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

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

  219.               if (fb_depth == 16) {

  221.                      unsigned short color;

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

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

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

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

  231.                      }

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

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

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

  239.               }

  241.               y++; // next scanline

  243.        }

  245.        /*

  247.         * finish decompress, destroy decompress object

  249.         */

  251.        jpeg_finish_decompress(&cinfo);

  253.        jpeg_destroy_decompress(&cinfo);

  255.        /*

  257.         * release memory buffer

  259.         */

  261.        free(buffer);

  263.        /*

  265.         * close jpeg inputing file

  267.         */

  269.        fclose(infile);

  271.        /*

  273.         * unmap framebuffer's shared memory

  275.         */

  277.        fb_munmap(fbmem, screensize);

  279.        /*

  281.         * close framebuffer device

  283.         */

  285.        fb_close(fbdev);

  287.        return (0);

  289. }

  291. void

  293. usage(char *msg)

  295. {

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

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

  301. }

  303. /*

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

  307.  */

  309. unsigned short

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

  313. {

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

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

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

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

  323. }

  325. /*

  327.  * open framebuffer device.

  329.  * return positive file descriptor if success,

  331.  * else return -1.

  333.  */

  335. int

  337. fb_open(char *fb_device)

  339. {

  341.        int fd;

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

  345.               perror(__func__);

  347.               return (-1);

  349.        }

  351.        return (fd);

  353. }

  355. /*

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

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

  361.  */

  363. int

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

  367. {

  369.        struct fb_fix_screeninfo fb_finfo;

  371.        struct fb_var_screeninfo fb_vinfo;

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

  375.               perror(__func__);

  377.               return (-1);

  379.        }

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

  383.               perror(__func__);

  385.               return (-1);

  387.        }

  389.        *width = fb_vinfo.xres;

  391.        *height = fb_vinfo.yres;

  393.        *depth = fb_vinfo.bits_per_pixel;

  395.        return (0);

  397. }

  399. /*

  401.  * map shared memory to framebuffer device.

  403.  * return maped memory if success,

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

  407.  */

  409. void *

  411. fb_mmap(int fd, unsigned int screensize)

  413. {

  415.        caddr_t fbmem;

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

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

  421.               perror(__func__);

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

  425.        }

  427.        return (fbmem);

  429. }

  431. /*

  433.  * unmap map memory for framebuffer device.

  435.  */

  437. int

  439. fb_munmap(void *start, size_t length)

  441. {

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

  445. }

  447. /*

  449.  * close framebuffer device

  451.  */

  453. int

  455. fb_close(int fd)

  457. {

  459.        return (close(fd));

  461. }

  463. /*

  465.  * display a pixel on the framebuffer device.

  467.  * fbmem is the starting memory of framebuffer,

  469.  * width and height are dimension of framebuffer,

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

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

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

  477.  */

  479. int

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

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

  485. {

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

  489.               return (-1);

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

  493.        *dst = color;

  495.        return (0);

  497. }


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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