Linux---libjpeg use (jpg to RGB)

One: Compilation of the Libjpeg library

Download the source code, after decompression

./configure--prefix=/xxxx CC=ARM-LINUX-GCC--host=arm-linux--enable-shared--enable-static

---xxxx for the creation of dynamic static pants directory

----CC for Cross compiler

-----enable-shared---enable-static the active Static library

Then make,

Make install again, generate the corresponding header files and libraries in the XXX directory

Jconfig.h jerror.h jmorecfg.h jpeglib.h and libjpeg.9.so.1.0 libjpeg.a

Program writing

Example for framebuffer JPG picture format turn rgb (565)

TEST.c

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <unistd.h>

#include <stdio.h>

#include <sys/mman.h>

#include <linux/fb.h>

#include <stdlib.h>

Header file

#include "Libinclude/jpeglib.h"

#include "Libinclude/jerror.h"

struct Fb_var_screeninfo var;

unsigned short *fbp;

Define Structure body

struct Jpeg_decompress_struct cinfo;

struct Jpeg_error_mgr jerr;

FILE * infile;

int main (int argc, char **argv)

{

int fd,screen_size,i,j;

unsigned short value;

int POS;

Char *rdata;

Char *tbmp[]={"bmp/t1.jpg", "bmp/t2.jpg", "bmp/t3.jpg", "bmp/t4.jpg",

"Bmp/t5.jpg", "bmp/t6.jpg", "bmp/t7.jpg", "bmp/t8.jpg", "bmp/t9.jpg",

"Bmp/t10.jpg", "Bmp/t11.jpg"};

char Tpos = 0;

FD = open ("/dev/fb0", O_RDWR);

if (fd<0)

Perror ("open");

IOCTL (Fd,fbioget_vscreeninfo,&var);

printf ("var x =%d, y =%d bits =%d".) \ n ", Var.xres, Var.yres,var.bits_per_pixel);

Screen_size = Var.xres *VAR.YRES*VAR.BITS_PER_PIXEL/8;

printf ("Screen_size is%d\n", screen_size);

FBP = (unsigned short *) mmap (0, screen_size, Prot_write | Prot_read, map_shared, FD, 0);

if (!FBP)

Goto Mmap_err;

Generate the corresponding variable

Cinfo.err = Jpeg_std_error (&jerr);

jpeg_create_decompress (&cinfo);

while (1)

{

Open picture File

if (infile = fopen (Tbmp[tpos], "rb") = = = NULL) {

fprintf (stderr, "can ' t open%s\n", "tu.jpg");

exit (1);

}

Tpos + +;

if (tpos>=11)

Tpos = 0;

Get header information

Jpeg_stdio_src=\ ' #\ ' "infile);

Jpeg_read_header (&cinfo, TRUE);

Allocating memory Storage bytes

Rdata= (char*) calloc (cinfo.image_width*cinfo.image_height*cinfo.num_components,1);

Start unpacking

Jpeg_start_decompress (&cinfo);

Jsamprow Row_pointer[1];

while (Cinfo.output_scanline < cinfo.output_height)

{

row_pointer[0] = & rdata[(cinfo.output_scanline) *cinfo.image_width*cinfo.num_components];

Jpeg_read_scanlines (&cinfo,row_pointer, 1);

}

End Decompression

Jpeg_finish_decompress (&cinfo);

Framebuffer fills the bytes just allocated

pos = 0;

for (i=0;i<var.yres;i++)

for (j=0;j<var.xres;j++)

{

rgb888 Turn rgb565

Value= ((rdata[pos]>>3) <<11) | ((rdata[pos+1]>>2) <<5) | (rdata[pos+2]>>3);

* (fbp+i*var.xres+j) = value;

POS +=3;

}

Sleep (3);

Fclose (infile);

}

Jpeg_destroy_decompress (&cinfo);

Munmap (FBP, screen_size);

Close (FD);

return 0;

Mmap_err:

Perror ("mmap\n");

return-1;

}

NOTE: JPG default decompression is rgb888

Used with dynamic libraries and static libraries

Static Library

At this point the test.c directory has test.c libjpeg.a

Jconfig.h jerror.h jmorecfg.h jpeglib.h

ARM-LINUX-GCC Test.c-o test-l./-ljpeg

Generate test put to board execution

Dynamic Library

At this time the test.c directory has test.c

Jconfig.h jerror.h jmorecfg.h jpeglib.h libjpeg.9.so.1.0

ARM-LINUX-GCC Test.c-o test-l./-l:libjpeg.9.so.1.0

Change the libjpeg.9.so.1.0 to libjpeg.9.so and put it in the Development Board/usr/lib directory

Generate test put to board execution

This article is from the "Guo Di Temple Technology Road" blog, please be sure to keep this source http://6902621.blog.51cto.com/6892621/1688052

Linux---libjpeg use (jpg to RGB)