Pixel matrix how to scale - c

Question

I'm doing a sierpinski's carpet program and i managed to create a PGM image from a matrix.I first create a char **matrix which has # or ' ' .# = white color , ' ' = black color, and then i create a int **pixels with values 0 or 255 for black and white, pretty simple. The matrix size is equal to number of iterations of sierpinski's carpet : for 3 iterations of the algorithm i have a resulting matrix(so image) of 27 by 27 pixels. How can i multiply this matrix in order to enlarge the resulting picture but keep the same image.Something like for each pixel i want it to be 4 pixels in the output image. C program.
EDIT: Code for printing a PGM image from a matrix of pixel values
void print(char fout[30],int **pixels,int width,int height){
int i,j;
FILE *f = fopen(fout,"w");
fprintf(f,"%s\n","P2");
fprintf(f,"%d %d\n",width,height);
fprintf(f,"%d\n",255);
for(i=height-1;i>=0;i--){
for(j=0;j<width;j++){
fprintf(f,"%d ",pixels[i][j]);
}
fprintf(f,"\n");
}
fclose(f);
}
Code for creating the pixel value matrix
for(i=0;i<size;i++)
for(j=0;j<size;j++)
if(basegrid[i][j] == ' ')
pixels[i][j]=0;
else
pixels[i][j]=255;

Answer 1

First you can create a larger matrix (of size: size * 2 by size * 2) and then fill it according to the pixels you had at first.
Something like this should work:
int main()
{
int **pixels;
int size;
int **enlarged;
int idx;
enlarged = malloc(2 * size * sizeof(int *));
for(idx = 0; idx != size; ++idx)
{
enlarged[idx] = malloc(2 * size * sizeof(int));
}
int row;
int col;
for(row = 0; row != size; ++row)
{
for(col = 0; col != size; ++col)
{
enlarged[row * 2][col * 2] = pixels[row][col];
enlarged[row * 2 + 1][col * 2] = pixels[row][col];
enlarged[row * 2][col * 2 + 1] = pixels[row][col];
enlarged[row * 2 + 1][col * 2 + 1] = pixels[row][col];
}
}
}
Note that I left out the code where you read size and fill pixels.
Hope this helps.