关于在嵌入式开发板上显示一张jpeg图片 -

#include "lcdjpg.h"
static char g_color_buf[FB_SIZE]={0};
static int g_fb_fd;
static int *g_pfb_memory;
/* video_chat.c 画中画显示的坐标 */
volatile int g_jpg_in_jpg_x;
volatile int g_jpg_in_jpg_y;
/****************************************************
*函数名称:file_size_get
*输入参数:pfile_path -文件路径
*返回值:-1 -失败
其他值 -文件大小
*说明:获取文件大小
****************************************************/
unsigned long file_size_get(const char *pfile_path)
{
unsigned long filesize = -1;
struct stat statbuff;
if(stat(pfile_path, &statbuff) < 0)
{
return filesize;
}
else
{
filesize = statbuff.st_size;
}
return filesize;
}
unsigned char bcc_check(unsigned char *buf, int n)
{
int i;
unsigned char bcc=0;
for(i = 0; i < n; i++)
{
bcc ^= *(buf+i);
}
return (~bcc);
}
//LCD画点
void lcd_draw_point(unsigned int x,unsigned int y, unsigned int color)
{
*(g_pfb_memory+y*800+x)=color;
}
int lcd_draw_jpg(unsigned int x,unsigned int y,const char *pjpg_path,char *pjpg_buf,unsigned int jpg_buf_size,unsigned int jpg_half)
{
//初始化LCD
g_fb_fd = open("/dev/fb0", O_RDWR);
if(g_fb_fd<0)
{
printf("open lcd error\n");
return -1;
}
g_pfb_memory = (int *)mmap( NULL, //映射区的开始地址，设置为NULL时表示由系统决定映射区的起始地址
FB_SIZE, //映射区的长度
PROT_READ|PROT_WRITE, //内容可以被读取和写入
MAP_SHARED, //共享内存
g_fb_fd, //有效的文件描述词
0 //被映射对象内容的起点
);
/*定义解码对象，错误处理对象*/
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
char *pcolor_buf = g_color_buf;
char *pjpg;
unsigned int i=0;
unsigned int color =0;
unsigned int count =0;
unsigned int x_s = x;
unsigned int x_e ;
unsigned int y_e ;
int jpg_fd;
unsigned int jpg_size;
unsigned int jpg_width;
unsigned int jpg_height;
if(pjpg_path!=NULL)
{
/* 申请jpg资源，权限可读可写 */
jpg_fd=open(pjpg_path,O_RDWR);
if(jpg_fd == -1)
{
printf("open %s error\n",pjpg_path);
return -1;
}
/* 获取jpg文件的大小 */
jpg_size=file_size_get(pjpg_path);
/* 为jpg文件申请内存空间 */
pjpg = malloc(jpg_size);
/* 读取jpg文件所有内容到内存 */
read(jpg_fd,pjpg,jpg_size);
}
else
{
jpg_size = jpg_buf_size;
pjpg = pjpg_buf;
}
/*注册出错处理*/
cinfo.err = jpeg_std_error(&jerr);
/*创建解码*/
jpeg_create_decompress(&cinfo);
/*直接解码内存数据*/
jpeg_mem_src(&cinfo,pjpg,jpg_size);
/*读文件头*/
jpeg_read_header(&cinfo, TRUE);
/*开始解码*/
jpeg_start_decompress(&cinfo);
if(jpg_half)
{
x_e = x_s+(cinfo.output_width/2);
y_e = y +(cinfo.output_height/2);
/*读解码数据*/
while(cinfo.output_scanline < cinfo.output_height)
{
pcolor_buf = g_color_buf;
/* 读取jpg一行的rgb值 */
jpeg_read_scanlines(&cinfo,(JSAMPARRAY)&pcolor_buf,1);
/* 再读取jpg一行的rgb值 */
jpeg_read_scanlines(&cinfo,(JSAMPARRAY)&pcolor_buf,1);
for(i=0; i<(cinfo.output_width/2); i++)
{
/* 获取rgb值 */
color = *(pcolor_buf+2);
color = color | *(pcolor_buf+1)<<8;
color = color | *(pcolor_buf)<<16;
/* 显示像素点 */
lcd_draw_point(x,y,color);
pcolor_buf +=6;
x++;
}
/* 换行 */
y++;
x = x_s;
}
}
else
{
x_e = x_s+cinfo.output_width;
y_e = y +cinfo.output_height;
/*读解码数据*/
while(cinfo.output_scanline < cinfo.output_height )
{
pcolor_buf = g_color_buf;
/* 读取jpg一行的rgb值 */
jpeg_read_scanlines(&cinfo,(JSAMPARRAY)&pcolor_buf,1);
for(i=0; i<cinfo.output_width; i++)
{
/* 获取rgb值 */
color = *(pcolor_buf+2);
color = color | *(pcolor_buf+1)<<8;
color = color | *(pcolor_buf)<<16;
/* 显示像素点 */
lcd_draw_point(x,y,color);
pcolor_buf +=3;
x++;
}
/* 换行 */
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