FAQ > Display a picture file in DOS


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FAQ > How do I... (Level 2) > Display a picture file in DOS

This item was added on: 2003/02/07

(Taken directly from Lightatdawn's FAQ)

Just a few notes: I'm not going to go into great detail here.

If you want to do this in Win32 it is easy.

If you want to do this in Console mode: You can't. Console mode won't do graphics. The End.

If you want to do this in DOS mode, this is more complicated. Check out www.wotsit.org for information regarding picture files of all kind. The actual code to do this is semi-long. I'll put it in anyhow. But just so you're warned, this example is quite limited. It's cut down to make it easier to understand. This will load "test.bmp" (This can be changed, obviously) from the running directory. It will first initialize mode 13 (320x200 screen with 256 col) and then load the BMP. It will only load an 8-bit bmp of a size less than the screen. The code can be adapted to read other types of BMP's quite easily. Here goes!


#include <dos.h> 
#include <stdio.h> 
#include <string.h> 
#include <conio.h> 

char far  *Screen;

/* Sets the display to VGA 320x200x256 */
void VGAScreen(void)
{
  union REGS  r;

  r.h.ah = 0;
  r.h.al = 0x13;
  int86(0x10, &r, &r);

  return;
}

/* Goes back to textmode */
void TextScreen(void)
{
  union REGS  r;

  r.h.ah = 0;
  r.h.al = 0x3;
  int86(0x10, &r, &r);

  return;
}

/* This sets a DAC register to a specific Red Green Blue-value */
int SetDAC(unsigned char DAC, unsigned char R, unsigned char G, unsigned char B)
{
  outportb(0x3C8, DAC);
  outportb(0x3C9, R);
  outportb(0x3C9, G);
  outportb(0x3C9, B);

  return(0);
}

int LoadBMP(void)
{
  struct BMPHeader
  {
    unsigned short  bfType;
    long            bfSize, bfReserved, bfOffBits, biSize, biWidth, biHeight;
    unsigned short  biPlanes, biBitCount;
    long            biCompression, biSizeImage, biXPelsPerMeter, 
                    biYPelsPerMeter, biClrUsed, biClrImportant;
  } Header;

  FILE *BMPFile;
  unsigned char c, Palette[256][4];
  char          *filename = "test.bmp";
  unsigned int  offset, lines, paddedWidth;

  /* This checks for the file */
  BMPFile = fopen(filename, "rb");

  if (BMPFile == NULL)
  {
    printf("Cant open file.");
    return(1);
  }

  /* Read the headerinformation */
  fread(&Header, 54, 1, BMPFile);

  if (Header.bfType != 19778 || Header.bfReserved != 0 || Header.biPlanes != 1)
  {
    /* Not a valid bitmap file - don't display */
    printf("Not a valid bitmap.");
    fclose(BMPFile);
    return(1);
  }

  if (Header.biCompression != 0)
  {
    /*Compressed file - don't display*/
    printf("Compressed file.");
    fclose(BMPFile);
    return(1);
  }

  if (Header.biBitCount != 8)
  {
    /*If the file is other than 8-bit dont read.*/
    printf("Not an 8-bit bitmap.");
    fclose(BMPFile);
    return(1);
  }

  if (Header.biWidth > 320 || Header.biHeight > 200)
  {
    /*If its larger than 320*200 dont load.*/
    printf("Size too large.");
    fclose(BMPFile);
    return(1);
  }

  /*Load the palette info*/
  fread(&Palette, 1024, 1, BMPFile);
  
  for (c = 0; c < 255; c++) 
    SetDAC(c, Palette[c][2] >> 2, Palette[c][1] >> 2, Palette[c][0] >> 2);
    
  offset = (100 + (Header.biHeight >> 1)) * 320 + 160 - (Header.biWidth >> 1);
  lines = 0;
  paddedWidth = Header.biWidth & 0xFFFC;
  
  if (Header.biWidth != paddedWidth) 
    paddedWidth += 4;

  /*Loop for reading lines*/
  while (lines < Header.biHeight)
  {
    fread(Screen + offset, paddedWidth, 1, BMPFile);
    offset -= 320;
    lines++;
  }

  fclose(BMPFile);
  return(0);
}

int main(int argcount, char *argvalue[])
{
  /* Set up a pointer in vga memory */
  Screen = (char far *) 0xA0000000L;
  VGAScreen();
  LoadBMP();
  getch();
  TextScreen();
  return(0);
}

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