Question

I am trying to write simple pgm file reading C program. I had to create simple structure:

typedef struct pgmImage {
   int R; //rows
   int C; //collumns
   int G; //grey scale
   int **pix;  // array of pixels
}Image;

Now i have to initialize empty Image structure.I need one to set all variables based on *.pgm file in other function.
All the time i am getting “unable to read memory” and ‘unitialized local variable x used’. I have tried to simply do :

Image *x=0;

but program crashes when read function try to set R,C,G values.

Answer 1

If you want a pointer to Image you have to initialize like this.

Image *x = NULL;

Accessing the image (x) camps like this :

x-> C = 0;
x-> ...
x->pix = NULL;

But first you need to allocate memory to your image.

x = (Image*) malloc(sizeof(Image));