将jpeg图片显示在framebuffer上

最新推荐文章于 2024-03-29 09:51:39 发布

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本文介绍了一个使用C语言编写的程序，该程序能够读取JPEG格式的图片文件，并将其解码后绘制到帧缓冲区上显示。程序首先打开指定的JPEG文件和帧缓冲设备，获取帧缓冲区的相关信息，然后利用libjpeg库进行JPEG解码，并将RGB数据转换为帧缓冲区支持的颜色格式。

/**************************************************

 * example5.c

 * Author: T-bagwell

 *

 * Compile:gcc -Wall example5.c -o
 example5

 *************************************************/

#include <stdio.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <linux/fb.h>

#include <errno.h>

#include <sys/mman.h>

#include <stdlib.h>

#include <string.h>

#include <sys/ioctl.h>

#include <jpeglib.h>

#include <jerror.h>

int print_screen(short *buf,int width,int height);

void draw_hline(short *buffer,int x,int y,int maxy,int maxx);

char *fb_addr;

unsigned int fb_width;

unsigned int fb_height;

unsigned int fb_depth;

unsigned fb_size;

unsigned short PIXELRGB888TO565(unsigned char red, unsigned char green, unsigned
 char blue)

{

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

        unsigned short G = ((green >> 3) << 5) & 0x07E0;

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

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

}

int draw_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);

}

int main(int argc, char *argv[])

{

        int screen_fbd=0;

        struct jpeg_decompress_struct cinfo;

        struct jpeg_error_mgr jerr;

        FILE *infile;

        struct fb_fix_screeninfo fb_fix;

        struct fb_var_screeninfo fb_var;

        char *env=NULL;

        unsigned char *buffer;

        unsigned char *fbmem;

        short *color_white;

        unsigned short color;

        unsigned int x;

        unsigned int y;

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

        {

                fprintf(stderr, "open bbs.chinaffmpeg.com 孙悟空提醒您 %s failed\n", argv[1]);

                exit(-1);

        }

        if(!(env = getenv("FRAMEBUFFER")))

        {

                env = "/dev/fb0";

        }

        screen_fbd = open(env, O_RDWR);

        if(screen_fbd < 0)

        {

                return 0;

        }

        if(ioctl(screen_fbd, FBIOGET_VSCREENINFO, &fb_var) == -1)

        {

                close(screen_fbd);

                return 0;

        }

        fb_width = fb_var.xres;

        fb_height = fb_var.yres;

        fb_depth = fb_var.bits_per_pixel;

        cinfo.err = jpeg_std_error(&jerr);

        jpeg_create_decompress(&cinfo);

        jpeg_stdio_src(&cinfo, infile);

        jpeg_read_header(&cinfo, TRUE);

        jpeg_start_decompress(&cinfo);

        if ((cinfo.output_width > fb_width) ||(cinfo.output_height > fb_height))

        {

                return (-1);

        }

        fbmem = mmap(0, fb_width * fb_height, PROT_READ | PROT_WRITE, MAP_SHARED, screen_fbd, 0);

        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)

                {

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

                        {

                                color = PIXELRGB888TO565(buffer[x * 3], buffer[x * 3 + 1], buffer[x * 3 + 2]);

                                draw_pixel(fbmem, fb_width, fb_height, x, y, color);

                        }

                }

        y++;

        }

        jpeg_finish_decompress(&cinfo);

        jpeg_destroy_decompress(&cinfo);

        free(buffer);

        return 0;

}

QQ群里突然有人问了这个问题，希望得到开源的程序，正好以前写过一个，找的挺费劲的，就贴到这里吧
http://bbs.chinaunix.net/forum.php?mod=redirect&goto=findpost&ptid=2021099&pid=14296454&fromuid=11344913