
平台论坛博客文库

› 论坛 › 程序设计 › 嵌入式开发 › 在Linux控制台下显示JPEG图像

在Linux控制台下显示JPEG图像 [复制链接]

myforever

小富即安

论坛徽章:: 0

电梯直达

1楼 [收藏(0)] [报告]

发表于 2008-10-29 11:59 |只看该作者 |倒序浏览

/*
* $Id: fv.c
* $Desp: draw jpeg to framebuffer
* $Author: rockins
* $Date: Wed Jan 3 20:15:49 CST 2007
*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <jpeglib.h>
#include <jerror.h>
#define FB_DEV "/dev/fb0"
/***************** function declaration ******************/
void usage(char *msg);
unsigned short RGB888toRGB565(unsigned char red,
unsigned char green, unsigned char blue);
int fb_open(char *fb_device);
int fb_close(int fd);
int fb_stat(int fd, int *width, int *height, int *depth);
void *fb_mmap(int fd, unsigned int screensize);
int fb_munmap(void *start, size_t length);
int fb_pixel(void *fbmem, int width, int height,
int x, int y, unsigned short color);
/************ function implementation ********************/
int
main(int argc, char *argv[])
{
/*
* declaration for jpeg decompression
*/
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
FILE *infile;
unsigned char *buffer;
/*
* declaration for framebuffer device
*/
int fbdev;
char *fb_device;
unsigned char *fbmem;
unsigned int screensize;
unsigned int fb_width;
unsigned int fb_height;
unsigned int fb_depth;
unsigned int x;
unsigned int y;
/*
* check auguments
*/
if (argc != 2) {
usage("insuffient auguments");
exit(-1);
}
/*
* open framebuffer device
*/
if ((fb_device = getenv("FRAMEBUFFER")) == NULL)
fb_device = FB_DEV;
fbdev = fb_open(fb_device);
/*
* get status of framebuffer device
*/
fb_stat(fbdev, &fb_width, &fb_height, &fb_depth);
/*
* map framebuffer device to shared memory
*/
screensize = fb_width * fb_height * fb_depth / 8;
fbmem = fb_mmap(fbdev, screensize);
/*
* open input jpeg file
*/
if ((infile = fopen(argv[1], "rb")) == NULL) {
fprintf(stderr, "open %s failed\n", argv[1]);
exit(-1);
}
/*
* init jpeg decompress object error handler
*/
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
/*
* bind jpeg decompress object to infile
*/
jpeg_stdio_src(&cinfo, infile);
/*
* read jpeg header
*/
jpeg_read_header(&cinfo, TRUE);
/*
* decompress process.
* note: after jpeg_start_decompress() is called
* the dimension infomation will be known,
* so allocate memory buffer for scanline immediately
*/
jpeg_start_decompress(&cinfo);
if ((cinfo.output_width > fb_width) ||
(cinfo.output_height > fb_height)) {
printf("too large JPEG file,cannot display\n");
return (-1);
}
buffer = (unsigned char *) malloc(cinfo.output_width *
cinfo.output_components);
y = 0;
while (cinfo.output_scanline < cinfo.output_height) {
jpeg_read_scanlines(&cinfo, &buffer, 1);
if (fb_depth == 16) {
unsigned short color;
for (x = 0; x < cinfo.output_width; x++) {
color = RGB888toRGB565(buffer[x * 3],
buffer[x * 3 + 1], buffer[x * 3 + 2]);
fb_pixel(fbmem, fb_width, fb_height, x, y, color);
}
} else if (fb_depth == 24) {
memcpy((unsigned char *) fbmem + y * fb_width * 3,
buffer, cinfo.output_width * cinfo.output_components);
}
y++; // next scanline
}
/*
* finish decompress, destroy decompress object
*/
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
/*
* release memory buffer
*/
free(buffer);
/*
* close jpeg inputing file
*/
fclose(infile);
/*
* unmap framebuffer's shared memory
*/
fb_munmap(fbmem, screensize);
/*
* close framebuffer device
*/
fb_close(fbdev);
return (0);
}
void
usage(char *msg)
{
fprintf(stderr, "%s\n", msg);
printf("Usage: fv some-jpeg-file.jpg\n");
}
/*
* convert 24bit RGB888 to 16bit RGB565 color format
*/
unsigned short
RGB888toRGB565(unsigned char red, unsigned char green, unsigned char blue)
{
unsigned short B = (blue >> 3) & 0x001F;
unsigned short G = ((green >> 2) << 5) & 0x07E0;
unsigned short R = ((red >> 3) << 11) & 0xF800;
return (unsigned short) (R | G | B);
}
/*
* open framebuffer device.
* return positive file descriptor if success,
* else return -1.
*/
int
fb_open(char *fb_device)
{
int fd;
if ((fd = open(fb_device, O_RDWR)) < 0) {
perror(__func__);
return (-1);
}
return (fd);
}
/*
* get framebuffer's width,height,and depth.
* return 0 if success, else return -1.
*/
int
fb_stat(int fd, int *width, int *height, int *depth)
{
struct fb_fix_screeninfo fb_finfo;
struct fb_var_screeninfo fb_vinfo;
if (ioctl(fd, FBIOGET_FSCREENINFO, &fb_finfo)) {
perror(__func__);
return (-1);
}
if (ioctl(fd, FBIOGET_VSCREENINFO, &fb_vinfo)) {
perror(__func__);
return (-1);
}
*width = fb_vinfo.xres;
*height = fb_vinfo.yres;
*depth = fb_vinfo.bits_per_pixel;
return (0);
}
/*
* map shared memory to framebuffer device.
* return maped memory if success,
* else return -1, as mmap dose.
*/
void *
fb_mmap(int fd, unsigned int screensize)
{
caddr_t fbmem;
if ((fbmem = mmap(0, screensize, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0)) == MAP_FAILED) {
perror(__func__);
return (void *) (-1);
}
return (fbmem);
}
/*
* unmap map memory for framebuffer device.
*/
int
fb_munmap(void *start, size_t length)
{
return (munmap(start, length));
}
/*
* close framebuffer device
*/
int
fb_close(int fd)
{
return (close(fd));
}
/*
* display a pixel on the framebuffer device.
* fbmem is the starting memory of framebuffer,
* width and height are dimension of framebuffer,
* x and y are the coordinates to display,
* color is the pixel's color value.
* return 0 if success, otherwise return -1.
*/
int
fb_pixel(void *fbmem, int width, int height,
int x, int y, unsigned short color)
{
if ((x > width) || (y > height))
return (-1);
unsigned short *dst = ((unsigned short *) fbmem + y * width + x);
*dst = color;
return (0);
}

复制代码

[ 本帖最后由 myforever 于 2008-10-29 12:01 编辑 ]

文库|博客

myforever

小富即安

论坛徽章:: 0

2楼 [报告]

发表于 2008-10-29 12:03 |只看该作者

原本把原理也贴过来，帖子拍版有问题，所有就不引了

大家有兴趣来这儿看看

在Linux控制台下显示JPEG图像

http://www.b2tang.com/viewthread.php?tid=113&extra=page%3D5

实战分享：从技术角度谈机器学习入门| 【大话IT】RadonDB低门槛向MySQL集群下战书 | ChinaUnix打赏功能已上线！ | 新一代分布式关系型数据库RadonDB知多少？

返回列表

Chinaunix › 论坛 › 程序设计 › 嵌入式开发 › 在Linux控制台下显示JPEG图像