#define BUFFERSIZE 1024

#define unchar unsigned char

static unchar iDataR[BUFFERSIZE][BUFFERSIZE]; // Red buffer.
static unchar iDataG[BUFFERSIZE][BUFFERSIZE]; // Green or BW buffer.
static unchar iDataB[BUFFERSIZE][BUFFERSIZE]; // Blue buffer.

/********************************************************************/
/* Unix PGM access routines                                         */
/********************************************************************/
/****************************************/
/* PGM filename prompt.                 */  
/****************************************/
void pgmFileName(char FileName[80], char *Prompt)
{
   printf("* Enter a %s filename: ", Prompt);
   scanf("%s", FileName);
   printf("\n");
}

/****************************************/
/* Clear comments from PGM file.	*/
/****************************************/
void pgmCommentClear(FILE *disk)
{
int    data;
int    err;
long   l;
unsigned char ch;
fpos_t *pos;
   pos = &l;
   fread(&ch, 1, 1, disk);
   err = fgetpos(disk, pos);
   fread(&ch, 1, 1, disk);
   if (ch == '#') {
      while (ch == '#') {
         while (ch != '\n') fread(&ch, 1, 1, disk);
         err = fgetpos(disk, pos);
         fread(&ch, 1, 1, disk);
      }
      err = fsetpos(disk, pos);      
   } else {
      err = fsetpos(disk, pos);
   }
}

/****************************************/
/* PGM file load.                       */  
/****************************************/
void pgmLoad(char FileName[80], int *xSize, int *ySize, int *color)
{ 
int    x, y;
int    xmax, ymax;
int    pmax;
int    cFlag;
unchar *ptrR, *ptrG, *ptrB;
char   ch;
char   type[3];
FILE   *disk;

   // Open file for reading.
   printf("* Loading PGM file: %s \n", FileName);
   if ((disk = fopen(FileName, "rb")) == NULL) {
      printf(">> ERROR - Cannot open PGM file.\n");
      return;
   }

   // Read in file header.
   fscanf(disk, "%s", &type);
   pgmCommentClear(disk);
   fscanf(disk, "%d", &xmax);
   fscanf(disk, "%d", &ymax);
   fscanf(disk, "%d", &pmax);
   fread(&ch, 1, 1, disk);

   // Check file.
   if (strcmp(type, "P5") == 0) {
      cFlag = 0;
   } else {
      if (strcmp(type, "P6") == 0) {
         cFlag = 1;
      } else {
         printf(">> ERROR - Incorrect PGM format.\n");
         fclose(disk);
         return;
      }
   }  
   if (xmax > BUFFERSIZE) {
      printf(">> ERROR - Image is too big.\n");
      fclose(disk);
      return;
   }  
   if (ymax > BUFFERSIZE) {
      printf(">> ERROR - Image is too big.\n");
      fclose(disk);
      return;
   }  
   if (pmax > 255) {
      printf(">> ERROR - Image is too deep.\n");
      fclose(disk);
      return;
   }  

   // Clear buffers.
   for (y = 0; y < BUFFERSIZE; y++) {
       ptrR = iDataR[y];
       ptrG = iDataG[y];
       ptrB = iDataB[y];
       for (x = 0; x < BUFFERSIZE; x++) {
           *ptrR = 0;
           *ptrG = 0;
           *ptrB = 0;
           ptrR++;
           ptrG++;
           ptrB++;
       }
   }

   if (cFlag == 0) {
      // Load b/w image.
      for (y = 0; y < ymax; y++) {
          ptrG = iDataG[y];
          for (x = 0; x < xmax; x++) {
              *ptrG = getc(disk);
              ptrG++;
          }
      }
   } else {
      // Load color image.
      for (y = 0; y < ymax; y++) {
          ptrR = iDataR[y];
          ptrG = iDataG[y];
          ptrB = iDataB[y];
          for (x = 0; x < xmax; x++) {
              *ptrR = getc(disk);
              *ptrG = getc(disk);
              *ptrB = getc(disk);
              ptrR++;
              ptrG++;
              ptrB++;
          }
      }
   }
   fclose(disk);

   // Return image size and color.;
   *xSize = xmax;
   *ySize = ymax;
   *color = cFlag;
}

/****************************************/
/* PGM file save.                       */  
/****************************************/
void pgmSave(char FileName[80], int xSize, int ySize, int cFlag)
{
int    x, y;
unchar *ptrR, *ptrG, *ptrB; 
FILE   *disk;

   // Open file for writing.
   printf("* Saving PGM file: %s \n", FileName);
   disk = fopen(FileName, "wb");

   // Write file header.
   if (cFlag == 0) fprintf(disk, "P5\n");
              else fprintf(disk, "P6\n");
   fprintf(disk, "%d %d\n", xSize, ySize);
   fprintf(disk, "255\n");

   if (cFlag == 0) {
      // Write BW data.
      for (y = 0; y < ySize; y++) {
          ptrG = iDataG[y];
          for (x = 0; x < xSize; x++) {
              putc(*ptrG, disk);
              ptrG++;
          }
      }  
   } else {
      // Write color data.
      for (y = 0; y < ySize; y++) {
          ptrR = iDataR[y];
          ptrG = iDataG[y];
          ptrB = iDataB[y];
          for (x = 0; x < xSize; x++) {
              putc(*ptrR, disk);
              putc(*ptrG, disk);
              putc(*ptrB, disk);
              ptrR++;
              ptrG++;
              ptrB++;
          }
      }
   }
   fclose(disk);
}