PLMBase Component : 2D Video

Overview
Classes
Examples

Overview

This section deals with graphic output. So here, you will find classes to initialise the screen (in fullscreen or windowed mode), to draw some basic primitives and write some text, and to create and copy images.

Classes

PLMColor : Simple type definition (in fact a 32 bits integer). Can be used to store a color in any color depth.
PLMDrawable : Virtual class that defines an interface with drawing primitives (lines, rectangle, circle, text and blits).
PLMScreen : Main class to access video hardware (singleton, only one instance). Derives from PLMDrawable.
PLMImage : Usually called a surface, this object is used to store any graphic data out of the screen, like sprites, textures... Derives from PLMDrawable. Can load (and save) data from different file formats (PCX, GIF, BMP, TGA).
PLMFont : Internal format, bitmap font, to be used with PLMDrawable objects.
PLMPal : Stores any number of color definitions (32 bits RGBA).
PLMVideoMode : A simple class to query the system for available video modes (fullscreen).

Examples

This first example shows how to initialise a screen from command-line arguments :

bool init_screen (int argc, char *argv[])
{
  u32 flags = 0;
  u32 width = 640, height = 480, depth = 8;
  int i;
  // parse command line to set screen depth and fullscreen
  for (i = 1; i < argc; ++i)
    {
      if (strcmp (argv[i], "-full") == 0)
        flags |= PLMScreen::FULL;
      else if (strcmp (argv[i], "-8") == 0)
        depth = 8;
      else if (strcmp (argv[i], "-16") == 0)
        depth = 16;
      else if (strcmp (argv[i], "-24") == 0)
        depth = 24;
      else if (strcmp (argv[i], "-32") == 0)
        depth = 32;
      else
        cout << "> arg " << argv[i] << " ignored\n";
    }
  if (argc > 1)
    {
      cout << "You asked: " << width << " x " << height
           << " x " << depth << " bpp, ";
      if (flags & PLMScreen::FULL)
        cout << "fullscreen\n";
      else
        cout << "windowed\n";
    }
  // get an instance of the screen object
  PLMScreen *screen = PLMScreen::GetInstance ();
  ASSERT (screen);
  
  // init screen with command-line parameters
  if (! screen->Init (width, height, flags, depth))
    {
      cerr << "Can not init screen\n";
      return false;
    }
  
  // look at the parameters we actually got
  width  = screen->Width ();
  height = screen->Height ();
  depth  = screen->Depth ();
  cout << "You got: " << width << " x " << height
       << " x " << depth << " bpp\n";
  cout << "SDL flags: " << screen->Flags () << endl;
  return true;
}

The second example shows how to draw something on a PLMDrawable object, here a screen :

  // lines
  for (i = 0; i < 40; i++)
    {
      screen->HLine (10, 10+i*2, 300, i);
      screen->HLine (10, 11+i*2, 300, i);
      screen->VLine (410+i*2, 10, 80, i);
      screen->VLine (411+i*2, 10, 80, i);
      screen->Line (470, 280, 550, 100+i*9, i);
      screen->Line (630, 280, 550, 100+i*9, i);
    }
  // shapes
  PLMColor col = screen->RGB2Col (255, 0, 0);  // red
  screen->Frame (20, 380, 80, 80, col);
  screen->Rectangle (120, 380, 80, 80, col);
  screen->Circle (280, 420, 40, col);
  screen->Disk (380, 420, 40, col);
  // gradients
  PLMColor col2 = screen->RGB2Col (255, 255, 0);  // yellow
  screen->Gradient (20, 320, 80, 40, red, yellow, PLMDrawable::GRAD_WE);
  screen->Gradient (120, 320, 80, 40, red, yellow, PLMDrawable::GRAD_NS);
  screen->Refresh();

Do not forget to call Refresh() to update the screen content, otherwise you won't see anything. Another usual error is to forget to delete the screen when the program is terminated.

Then we can write some text :

  // load the font gui.font (in the current directory)
  PLMFont font ("gui.font");
  font.PrintInfo (false);
  // write some text at the edge of the screen to test clipping
  PLMColor col = screen->RGB2Col (255, 0, 0);  // red
  char *text = "0123456789";
  screen->PutPixel (9, 3, col);
  screen->DrawText (10, 3, text, col, &font, FONT_LINE);
  screen->DrawText (10, height-9, text, col, &font, FONT_TOP);
  screen->DrawText (-3, 182, text, col, &font, FONT_TOP);
  screen->DrawText (width-37, 182, text, col, &font, FONT_TOP);
  screen->Refresh();

And finally load an image and copy it to the screen :

  // load a PCX image from the file sprite.pcx
  PLMImage img;
  // img needs a PLMResFile object to read its data from
  PLMResFile f ("sprite.pcx");
  if (! f.Good() || ! img.Load (f))
    {
      cerr << "Error loading image sprite.pcx\n";
      return;
    }
  // read the color of the first pixel (0,0)
  PLMColor key = img.GetPixel (0, 0);
  
  // copy the image on the screen at position (10,100),
  // using color 'key' as transparent color
  screen->CopyFrom (10, 100, key, &img);
  screen->Refresh();