Image descriptors

Hello, well I'm new at programming and C++, but for a program I am developing I need to use an image descriptor for a function that gets the RGB values from the image descriptor (the functions are from http://www.catenary.com) anyway I'm not sure I'm understanding everything about an image descriptor. I have read a few things about them and understand that they contain information about the image. It seems in the sample code I'm using though the image descriptor is never intialized. I need to have the image descriptor referring to an image on file (more specifically I need it to access the last photo saved by my program but that's not really relevant). So can anyone describe a way to do this or if this is even how image descriptors work?

Code:

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int loadjpgfilefrombuffer(LPTSTR fname, imgdes *image)
  {
  #define BAD_READ -87
 
  JpegData jdat;      // Reserve space for struct
  DWORD bytesRead,
  int rcode = NO_ERROR;
  OFSTRUCT of_st;
  UCHAR huge *jpegbuff;
  HANDLE fhandle;
  DWORD filesize;
 
  // Load JPEG file into buffer
  fhandle = CreateFile(fname, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_ NORMAL, NULL);
  if(fhandle == INVALID_HANDLE_VALUE)
      return(BAD_OPN);
  // Get filesize
  filesize = GetFileSize(fhandle, NULL);

  CloseHandle(fhandle);  // Close the file
 
  // Allocate memory to hold file
  jpegbuff = (UCHAR huge *)GlobalAllocPtr(GMEM_MOVEABLE, filesize);
  if(jpegbuff == 0)
      return(BAD_MEM);  // Allocation failed!
     
  // Load JPEG file into memory
  fhandle = CreateFile(fname, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_ NORMAL, NULL);
  if(fhandle == INVALID_HANDLE_VALUE)
      return(BAD_OPN);

  ReadFile(fhandle, jpegbuff, filesize, &bytesRead, NULL);
  if(bytesRead == 0)
      rcode = BAD_READ;
  CloseHandle(fhandle);  // Close the file
 
  // Read the JPEG data from the buffer
  // Make sure JPEG data exists and get image dimensions
  rcode = jpeginfofrombuffer(jpegbuff, &jdat);
  if(rcode == NO_ERROR) {
      // Release the current image buffer
      freeimage(image);
      // Allocate the new image buffer to the file dimensions
      // This allocates a DIB to hold the image
      rcode = allocimage(image, jdat.width, jdat.length, jdat.vbitcount);
      if(rcode == NO_ERROR) {
        // Decompress the JPEG data
        rcode = loadjpgfrombuffer(jpegbuff, image);
        } 
      }
  GlobalFreePtr(jpegbuff); // Free allocated memory
  // Now the image is in the DIB and ready to process, display, or print
  return(rcode);
}

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this is the sample code I was given that I am currently trying to get to work but it is saying image unitialized

Quote:

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Originally Posted by syg19

this is the sample code I was given that I am currently trying to get to work but it is saying image unitialized

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Who (or what) a where is saying "image unitialized"?
Besides, why are you closing the file and then opening it again with the same attributes?

Well the program compiles fine but when I try to take a picture (which is the action that initiates this code) I get an error message saying "Run-Time Check Failure #3 - The variable 'image' is being used without being initialized." As to your other question I don't really know I'm trying to use image processing tools provided by catenary.com this is a "sample" code they provide which I'm trying to get to work before.