variable initialization error...

:confused: :(
I am working on two different programs that use pgm pictures and make changes to each picture using histogram equilization and connected componet labeling. Now I am having 3 errors which eventhough i tried different things I can fix. Here there are:

histogram equilization
error: local variables h, w used wout been initialize(lines in bold)

Code:

---

#include <iostream>
#include <fstream>
#include <cmath>
#include <cstdio>

using namespace std;

void read_pgm(char * file_name)
{    int w, h;
          char buf[80];
        FILE        * fp;
        int cor [256][256];
        // open file for reading
        if((fp = fopen(file_name, "r")) == NULL) {
        fprintf(stderr, "readImage: Can't open %s\n", file_name);
                exit(1);
        }

          // Verify that the image is in PGM format.
          fgets(buf, 70, fp);
          if(strncmp(buf,"P5",2) != 0){
                      fprintf(stderr, "The file %s is not in PGM format", file_name);
                      fclose(fp);
                      exit(1);
          }

        // skip all comment lines
          do { fgets(buf, 70, fp); } while(buf[0] == '#');   
        sscanf(buf, "%d %d", &w, &h);
          do { fgets(buf, 70, fp); } while(buf[0] == '#');

        // read intensity values into memory
        //assign_mem(w, h); // assign a 2-D array cor for the image
        for (int i = 0; i < w; i++)
          for (int j = 0; j < h; j++)
            cor[i][j] = getc(fp);
        if (feof(fp) != 0) {
          printf("something is wrong with this picture.\n");
          exit(1);
        }
        fclose(fp);
}

// writes pgm grey scale image into memory cor[i][j]
void write_pgm(char * file_name)
{
        //int h,w;
        FILE        *out;
        int cor[256][256],h,w;

        if ((out = fopen(file_name, "wb")) == NULL) {
          cout << "write_pgm: cannot open the file "<<file_name<<" for writing";
            //cout << file_name ;
          //cout << " for writing";
          //cout << endl;
          exit(1);
        }
                       
        fprintf(out,"P5\n");
        fprintf(out,"%d %d\n", w, h);
        fprintf(out,"255\n");
        for (int i = 0; i < h; i++)
          for (int j = 0; j < w; j++)
            putc(int(cor[i][j]+0.5), out);
            // cor saves the image information

        fclose(out);
        return;
}
int main(){
        //read image
        read_pgm("lena.pgm");
                int h,w;
        char buf[80];
        long i;
        long sum;
        long hist[256];
        long sum_hist[256];
        long Npixels = (w*h);       
        float formula = Npixels / 255;
               
        //clear histogram to 0
        for (i=0; i < 256; i++)
                hist [i] = 0;
       
        //calculate the histogram sum
        for (i=0; i<Npixels; i++)
            hist[buf[i]]++;               
        sum = 0;
        for (i = 0; i< 256; i++){
                sum += hist[i];
                sum_hist [i]= (sum * formula) + 0.5;
        }

        //transfor image using new sum
        for (i = 0; i< Npixels; i++){
                buf[i] = (char) sum_hist[buf[i]]; 
        }

        //write image
        write_pgm("newlena.pgm");

return 0;
}

---

component labeling
using same read and write function as above program
error=Left of .getValue must have class/structure/union type(bold)

Code:

---

int main(){
        FILE *fp;
        read_pgm("lena.pgm");
        int i,j;
        int        w, h;
        int cor[256][256];
        int pixels[256];
        int thresh;

/******************** For Connected Components Only ********************
        Applying the Component Labeling algorithm on the input image.
*/
       
        //Step 1- Fill the Intensity array backward ..That is, 255,254,253 with increasing index
        //These value will work as label for us. Maximum label range can be 255

 for ( i=0;i<256;i++) //error message name lookup of 'i' change for new ISO 'for' scope
        {        pixels[i]= 255-i;        }

/***************For Connected Components Labeling only ******************
        //Step 2- Apply the Thresholding on input image*/
        for( i=0; i<w; i++)
        {
                for(j=0; j<h; j++)
                {    if(cor[i][j] < thresh)    {
                          cor[i][j] = 255;  }
                    else    {
                          cor[i][j] = 0;    }
                }
        }
        // Now we will label the components here
        for ( i=0; i<w;i++)
        {
                for(j=0;j<h;j++)
                {    if(fp.getValue(i,j)==0)        {
                        //found a component by its neighbors...        }
                }
        }
        //Step 2-Map the image data with the Intensity array
        for ( i=0;i<w;i++)
        {    for (int j=0;j<h;j++){
                        cor[i][j] = pixels[cor[i][j]];
                }
        }
return 0;}

---

>> local variables h, w used wout been initialize(lines in bold)
I'm just curious. What is your interpretation of these warnings?

gg

1)Here is a description of fprintf():

Quote:

---

int fprintf (FILE * stream , const char * format [ , argument , ...] );

Print formatted data to a stream.
Prints to the specified stream a sequence of arguments formatted as the format argument specifies.

---

You never initialized h or w, nor did you ever assign them any values, yet your are trying to output them to a file:

Code:

---

int cor[256][256],h,w;
...
...
fprintf(out,"%d %d\n", w, h);

---

What you are doing is equivalent to this:

Code:

---

int w, h;
cout<<w<<h;

---

2) You normally use objects like this:

Apple myApple;
myApple.someFunction();

If you have a pointer to an object:

Apple* ptr;
Apple myApple;
ptr = &Apple;

you can't use the same notation:

ptr.someFunction(); //error

The dot operator is for objects of the class not pointers. If you dereference the pointer: *ptr, then that says to get the object at the address stored in the pointer. Since *ptr is an object, you could use the dot operator like this:

(*ptr).someFunction();

but since that notation is so cumbersome, C++ created this notation instead:

ptr->someFunction();

I make that mistake myself every so often. :(
But, if you are using a compiler like VC++6, and you type the dot after an object name, an autocomplete member list appears, so if you type the dot , and you don't see that members list, then it's a pretty good indication something is wrong.