// based on mat/examples/tutorials/ex16.c

static char help[] = "Reads a matrix from PETSc binary file and saves its structure as an image. \n\n";

/*
 Example:
      ./mat2img -f <matrix file> -size <size in pixels>
 */

#include <string.h>
#include <petscmat.h>
#include <petscdraw.h>

#define call(f) ierr=(f);CHKERRQ(ierr);


#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **args)
{
  Mat               A;
  PetscViewer       fd;                        /* viewer */
  char              file[PETSC_MAX_PATH_LEN];  /* input file name */
  PetscInt          size;
  PetscErrorCode    ierr;
  PetscBool         flg;
  PetscMPIInt       rank;

  PetscDraw draw;
  PetscViewer viewer;

  PetscInitialize(&argc,&args,(char*)0,help);
  call(MPI_Comm_rank(PETSC_COMM_WORLD,&rank));

  /* Determine files from which we read the linear systems. */
  call(PetscOptionsGetString(NULL,"-f",file,PETSC_MAX_PATH_LEN,&flg));
  if (!flg) {
    strcpy(file, "matrix.bin");
  }

  call(PetscOptionsGetInt(NULL,"-size",&size,&flg));
  if (!flg) {
    size = 600;
  }
  
  /* Open binary file.  Note that we use FILE_MODE_READ to indicate
     reading from this file. */
  call(PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd));

  /* Load the matrix; then destroy the viewer. */
  call(MatCreate(PETSC_COMM_WORLD,&A));
  call(MatSetFromOptions(A));
  call(MatLoad(A,fd));
  
  call(PetscViewerDrawOpen(PETSC_COMM_WORLD, PETSC_NULL, file, 100, 100, size, size, &viewer));
  call(MatView(A, viewer));
  call(PetscViewerDrawGetDraw(viewer, 0, &draw));
  call(PetscDrawFlush(draw));
  call(PetscDrawSetSave(draw, "matrix", PETSC_FALSE));
  call(PetscDrawSetSaveFinalImage(draw, "matrix2"));
  
  call(PetscViewerDestroy(&fd));

  call(MatDestroy(&A));
  call(PetscFinalize());
  return 0;
}