Thread: Reading a pgm file using visual C++

I want to read the pixel values from a pgm file, then compute the integral image and save the result to a text file. At first I used Dev C++ to compile my code, but the pixel values have segmentation faults(Only the first three rows are correct). My instructor said there were two small bugs in my code which caused segmentation faults, but I don't know where the bugs are. She also said that she cannot compile my code on visual studio, she wants me to send her a C++11 compliant version, what does that mean?

Code:

#include<iostream>
#include<string>
#include<fstream>
#include<sstream>

usingnamespace std;

int main()
{
    int row =0, col =0, num_of_rows =0, num_of_cols =0, bits;
    ifstream infile("testfile.pgm", ios::binary);
    stringstream ss;    
    string inputLine ="";

    getline(infile,inputLine);// read the first line : P5
    if(inputLine.compare("P5")!=0) cerr <<"Version error"<< endl;
    cout <<"Version : "<< inputLine << endl;

    getline(infile,inputLine);// read the second line : comment
    cout <<"Comment : "<< inputLine << endl;

    ss << infile.rdbuf();//read the third line : width and height
    ss >> num_of_cols >> num_of_rows;
    cout << num_of_cols <<" columns and "<< num_of_rows <<" rows"<< endl;

    int max_val;//maximum intensity value : 255
    ss >> max_val;
    cout<<max_val;

    unsignedchar pixel;
    unsignedint pixel_value[num_of_rows][num_of_cols];
    unsignedint integral[num_of_rows][num_of_cols];

    for(row =0; row < num_of_rows; row++){//record the pixel values
        for(col =0; col < num_of_cols; col++){
             ss >> pixel;
             pixel_value[row][col]= pixel;
        }
        cout << endl;
    }

    for(int i=0; i<num_of_cols;i++){//compute integral image
        integral[0][i]=integral[0][i-1]+pixel_value[0][i];      
    }   
    for(int i=0;i<num_of_rows; i++){
        integral[i][0]=integral[i-1][0]+pixel_value[i][0];
    }
    for(int i =1; i < num_of_rows; i++){  
    for(int j =1; j < num_of_cols; j++){
        integral[i][j]= integral[i -1][j]+ integral [i][j -1]- integral[i -1][j -1]+ pixel_value[i][j];       
        }
    }

    ofstream output1("pixel_value.txt");// output the intensity values of the pgm file
    for(int k=0; k<num_of_rows; k++)
    {
        for(int r=0; r<num_of_cols; r++)
        {
            output1 << pixel_value[k][r]<<" ";
        }
        output1 <<";"<< endl;
    }

    ofstream output2("integral_value.txt");// output the integral image
    for(int a=0; a<num_of_rows; a++)
    {
        for(int b=0; b<num_of_cols; b++)
        {
            output2 << integral[a][b]<<" ";
        }
        output2 <<";"<< endl;
    } 

infile.close();  
return0;  
}

Besides, when I used visual studio 2012 to compile the above code, I used dynamic array to redefine the two arrays:

Code:

int**pixel_value;
pixel_value =newint*[num_of_rows];
for(int i=0; i<num_of_rows;i++)
    pixel_value[i]=newint[num_of_cols];

int**integral;
integral =newint*[num_of_rows];
for(int i=0; i<num_of_rows;i++)
    integral[i]=newint[num_of_cols];

for(row =0; row < num_of_rows; row++){//record the pixel values
    for(col =0; col < num_of_cols; col++){
         ss >> pixel;
         pixel_value[row][col]= pixel;
    }
    cout << endl;
}

After I changed the code, the output text file was completely blank! It couldn't read any values from the pgm file, does anyone know how to solve the problems? I really need to compile the code on visual studio 2012.

I haven't looked at the code yet, but please post your code again like so:

Code:

[code]
Your code here...
[/code]

...and make sure you use clear indentation. This will greatly improve your chances of getting help.

Regarding Visual Studio, is there a reason you haven't switched to the 2015 Community Edition? C++11/14 support has been lagging behind a bit with Microsoft's compiler suite, so getting a recent version is a good idea in most cases.

I have revised the declaration of the array and some invalid index values, but when I was compiling, an error message showed up: error 0xC0000005. I'm not what that means, is there something wrong about the memory?
I'm using VS2012 because my instructor uses it to compile the code, so I have to make sure that my code can be compiled on VS2012.

Code:

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>


using namespace std;


int main()
{
int row = 0, col = 0, num_of_rows = 0, num_of_cols = 0;
stringstream ss; 
ifstream infile("tsukuba.pgm", ios::binary);


string inputLine = "";


getline(infile,inputLine); // read the first line : P5
if(inputLine.compare("P5") != 0) cerr << "Version error" << endl;
cout << "Version : " << inputLine << endl;

getline(infile,inputLine); // read the second line : comment
cout << "Comment : " << inputLine << endl;


ss << infile.rdbuf(); //read the third line : width and height
ss >> num_of_cols >> num_of_rows;
cout << num_of_cols << " columns and " << num_of_rows << " rows" << endl;


int max_val; //maximum intensity value : 255
ss >> max_val;
cout<<max_val;

unsigned char pixel;


    int **pixel_value = new int*[num_of_rows];
for(int i = 0; i < num_of_rows; ++i) {
pixel_value[i] = new int[num_of_cols];
}


    int **integral = new int*[num_of_rows];
for(int i = 0; i < num_of_rows; ++i) {
integral[i] = new int[num_of_cols];
}


for (row = 0; row < num_of_rows; row++){ //record the pixel values
for (col = 0; col < num_of_cols; col++){
ss >> pixel;
pixel_value[row][col]= pixel;
}
cout << endl;
}


    integral[0][0]=pixel_value[0][0]; 
    for(int i=1; i<num_of_cols;i++){ //compute integral image
        integral[0][i]=integral[0][i-1]+pixel_value[0][i];        
    }    
    for (int i=1;i<num_of_rows; i++){
        integral[i][0]=integral[i-1][0]+pixel_value[i][0];
    }
        for (int i = 1; i < num_of_rows; i++){ 
    for (int j = 1; j < num_of_cols; j++){
    integral[i][j] = integral[i - 1 ][j] + integral [i][j - 1] - integral[i - 1] [j - 1] + pixel_value[i][j];         
        }
    }
    
ofstream output1("pixel_value.txt"); // output the intensity values of the pgm file
for (int k=0; k<num_of_rows; k++)
{
for (int r=0; r<num_of_cols; r++)
{
output1 << pixel_value[k][r] << " ";
}
output1 << ";" << endl;
}

ofstream output2("integral_value.txt"); // output the integral image
for (int a=0; a<num_of_rows; a++)
{
for (int b=0; b<num_of_cols; b++)
{
output2 << integral[a][b] << " ";
}
output2 << ";" << endl;
}


    for(int i = 0; i < num_of_rows; ++i) {
delete [] pixel_value[i];
    }
delete [] pixel_value;


    for(int i = 0; i < num_of_rows; ++i) {
delete [] integral[i];
    }
delete [] integral;


infile.close(); 
system("pause");
return 0;
}

I have revised the code, now I can run the code on visual studio 2012, and there were no segmentation faults,the header of the file can be read correctly, now the only problem is the pixel values were still not right, only the first two rows were correct.

Code:

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>


using namespace std;


int main()
{
    int row = 0, col = 0, num_of_rows = 0, num_of_cols = 0;
    stringstream ss;    
    ifstream infile("tsukuba.pgm", ios::binary);


    string inputLine = "";


    getline(infile,inputLine);      // read the first line : P5
    if(inputLine.compare("P5") != 0) cerr << "Version error" << endl;
    cout << "Version : " << inputLine << endl;
    
    getline(infile,inputLine);  // read the second line : comment
    cout << "Comment : " << inputLine << endl;


    ss << infile.rdbuf();   //read the third line : width and height
    ss >> num_of_cols >> num_of_rows;
    cout << num_of_cols << " columns and " << num_of_rows << " rows" << endl;


    int max_val;  //maximum intensity value : 255
    ss >> max_val;
    cout<<max_val;
    
    unsigned char pixel;


    int **pixel_value = new int*[num_of_rows];
    for(int i = 0; i < num_of_rows; ++i) {
        pixel_value[i] = new int[num_of_cols];
    }


    int **integral = new int*[num_of_rows];
    for(int i = 0; i < num_of_rows; ++i) {
        integral[i] = new int[num_of_cols];
    }


    for (row = 0; row < num_of_rows; row++){    //record the pixel values
        for (col = 0; col < num_of_cols; col++){
             ss >> pixel;
             pixel_value[row][col]= pixel;
        }
    }
    
    
    integral[0][0]=pixel_value[0][0];    
    for(int i=1; i<num_of_cols;i++){            //compute integral image
        integral[0][i]=integral[0][i-1]+pixel_value[0][i];        
    }    
    for (int i=1;i<num_of_rows; i++){
        integral[i][0]=integral[i-1][0]+pixel_value[i][0];
    }
        for (int i = 1; i < num_of_rows; i++){  
        for (int j = 1; j < num_of_cols; j++){
        integral[i][j] = integral[i - 1 ][j] + integral [i][j - 1] - integral[i - 1] [j - 1] + pixel_value[i][j];         
        }
    }
    
    ofstream output1("pixel_value.txt");  // output the intensity values of the pgm file
    for (int k=0; k<num_of_rows; k++)
    {
        for (int r=0; r<num_of_cols; r++)
        {
            output1 << pixel_value[k][r] << " ";
        }
        output1 << ";" << endl;
    }
    
    ofstream output2("integral_value.txt");    // output the integral image
    for (int a=0; a<num_of_rows; a++)
    {
        for (int b=0; b<num_of_cols; b++)
        {
            output2 << integral[a][b] << " ";
        }
        output2 << ";" << endl;
    }


    for(int i = 0; i < num_of_rows; ++i) {
        delete [] pixel_value[i];
    }
    delete [] pixel_value;


    for(int i = 0; i < num_of_rows; ++i) {
        delete [] integral[i];
    }
    delete [] integral;


infile.close();  
return 0;
}

Can you show me the tsukuba.pgm file? Attach it if it's too big, otherwise just paste its contents between code tags. Then I can probably guess why it doesn't work.

The file is attached(I changed the file extensions to txt in order to upload the file).

I also attached the text file I got using matlab. The pixel values of the two files become inconsistent from the middle of the third row.

Do you realize that the "P5" indicates a "binary" file? Shouldn't you be reading bytes probably using read()?

Jim