Thread: trouble using libjpeg

I am trying to get the sample code provided in libjpeg. i am getting some linker errors.
I followed the instructions provided in the following site
Compile LibJPEG

But i keep getting this linker error. The followin is my code

Code:

#include <stdio.h>
extern "C"
{
#include "jpeglib.h"
}
#include <setjmp.h>
#include <stdlib.h>
extern JSAMPLE *image_buffer;	/* Points to large array of R,G,B-order data */
int image_height = 576;	/* Number of rows in image */
int image_width = 768;		/* Number of columns in image */
GLOBAL(void) write_JPEG_file (char * filename, int quality)
{
	struct jpeg_compress_struct cinfo;
	struct jpeg_error_mgr jerr;
	FILE * outfile;
	JSAMPROW row_pointer[1];
	int row_stride;
	cinfo.err = jpeg_std_error(&jerr);
	jpeg_create_compress(&cinfo);
	if ((outfile = fopen(filename, "wb")) == NULL) {
    fprintf(stderr, "can't open %s\n", filename);
    exit(1);
  }
  jpeg_stdio_dest(&cinfo, outfile);
   cinfo.image_width = image_width; 	/* image width and height, in pixels */
  cinfo.image_height = image_height;
  cinfo.input_components = 3;		/* # of color components per pixel */
  cinfo.in_color_space = JCS_RGB; 


   jpeg_set_defaults(&cinfo);
   jpeg_set_quality(&cinfo, quality, TRUE);

   jpeg_start_compress(&cinfo, TRUE);
   row_stride = image_width * 3;



   while (cinfo.next_scanline < cinfo.image_height) {
	   row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride];
    (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
  }

   jpeg_finish_compress(&cinfo);
   fclose(outfile);
   jpeg_destroy_compress(&cinfo);

}
int main()
{
	write_JPEG_file("my_bitmap.bmp",3);
	return 0;

}

Can anyone tell me where i have gone wrong?

Without you telling us the errors you actually get, we can just guess based on historical trends. The historical trends say that you don't know how to work your compiler, and that you need to properly set up the project options/linker options to actually use the library (NOTE CAREFULLY: typing a #include line in your code does not do anything at all when it comes to actually bringing the library into a project).

Error 2 error LNK2019: unresolved external symbol _jpeg_destroy_compress referenced in function "void __cdecl write_JPEG_file(char *,int)" (?write_JPEG_file@@YAXPADH@Z) c:\Users\t_DivyaR\documents\visual studio 2010\Projects\jpeg-comp1\jpeg-comp1\t1.obj jpeg-comp1

Error 3 error LNK2019: unresolved external symbol _jpeg_finish_compress referenced in function "void __cdecl write_JPEG_file(char *,int)" (?write_JPEG_file@@YAXPADH@Z) c:\Users\t_DivyaR\documents\visual studio 2010\Projects\jpeg-comp1\jpeg-comp1\t1.obj jpeg-comp1

These are the type of errors i am getting. I followed all the instructions given in the link. Could you highlight on what needs to be done to set up the project in Visual Studio for working with libjpeg

You need to do what it says you should do:

Originally Posted by link above

For your Visual Studio Projects, select the project > open context menu > properties > configuration properties > linker > input > additional dependencies and add libjpeg.lib if you are building an executable or add libjpeg.lib to project > open context menu > properties > Configuration Properties > Librarian > Additional Dependencies if you are building a library.

Make sure you have put the .lib file where it belongs already.

But in there is no librarian in the context-menu->configuration. Also where can i find resources to work on libjpeg??

Are you trying to build a library? If not, then don't try to find that, because it isn't there. If so, make sure you set up your project as a library, and not a windows project or whatever.

I am encountering this error while linkin

Error 4 error LNK2019: unresolved external symbol "void __cdecl jpeg_start_compress(struct jpeg_compress_struct *,unsigned char)" (?jpeg_start_compress@@YAXPAUjpeg_compress_struct@ @E@Z) referenced in function _main

Any idea how to link my program to reference the libjpeg libraries?