Pfthb

I'm trying to read a BMP image (greyscales) with C, save values into an array, and convert this array to a string with values separated with a comma.

My program worked well under Windows 7 64-bit, but I had to move to Windows XP 32-bit because of library compatibility problems.

I have 1,750 images to read, and I want to store all of them in a single string.

When I launch my program it goes fine until the 509:th image, then I get a Segmentation Fault caused by fread(). Here's my code:

int i=0,j,k,num,len,length,l;
unsigned char *Buffer;
FILE *fp;
char *string,*finalstring;
char *query;
char tmp2[5],tmp[3];
query = (char *)malloc(sizeof(char)*200000000);
string = (char *)malloc(sizeof(char)*101376);
Buffer = (unsigned char *)malloc(sizeof(unsigned char)*26368);
 BITMAPFILEHEADER bMapFileHeader;
BITMAPINFOHEADER bMapInfoHeader;
length = 0;


 for (k =1;k<1751;k++)
 
 strcpy(link,"imagepath");
 //here just indexing the images from 0000 to 1750
 sprintf(tmp2,"%.4d",k);
 strcat(link,tmp2);
 strcat(link,".bmp");


 fp = fopen(link, "rb");
 num = fread(&bMapFileHeader,sizeof(BITMAPFILEHEADER),1,fp);
 num = fread(&bMapInfoHeader,sizeof(BITMAPINFOHEADER),1,fp);
 //seek beginning of data in bitmap
 fseek(fp,54,SEEK_SET);
 //read in bitmap file to data

 fread(Buffer,26368,1,fp);
 l=0;

 for(i=1024;i<26368;i++)
 
 itoa(Buffer[i],tmp,10);
 len = strlen(tmp);
 memcpy(string+l,tmp,len);
 memcpy(string+l+len,",",1);
 l = l+len+1;

 

 memcpy(query,"",1);
 memcpy(string,"",1);
 printf("%in",k);

 

Thanks

Make it tmp[4]; for three digits and the terminating 0.
Also: where is the fclose? I suspect that you're running out of file handles.
Check, whether fp != 0.

Where did you get 101376 from? Each of your bytes take up at most 5 characters as a decimal number with comma (e.g. -127,), 5*26368 is 131840.

Get rid of the casts in malloc calls. And #include <stdlib.h>.

What's the output of this program, in both the 64-bit and 32-bit systems you're using?

#include <stdio.h>
int main(void) 
 printf("sizeof (int) is %dn", (int)(sizeof (int)));
 printf("sizeof (int*) is %dn", (int)(sizeof (int*)));
 return 0;

1. Run your program in the debugger.




2. Set a breakpoint at the call to
   fread -- make it conditional on
   k==507 (this will stop it when you
   expect the fread to be successful).




3. When the program hits the
   breakpoint, examine the variables
   and check what is about to be passed
   to fread. The first one or two times
   you hit the breakpoint, the values
   will be good.




4. Then on the 509th time, you will
   probably see bogus values being passed
   to fread. Figure out where those
   bogus values are coming from --
   possibly set a conditional
   breakpoint on the variable being set
   to whatever the bogus value is.