Allegro Programming Tutorial, by Richard G Baldwin

Get and process a new image

Destroys the existing bitmap.
Sets the video mode for the window to the correct size.
Loads the same image file into a new bitmap.
Copies the new bitmap to the upper-left corner of the window.

By destroying the existing bitmap before setting the video mode:

Listing 4 satisfies the requirement described earlier.

Listing 4. Get and process a new image.

destroy_bitmap(picA); set_gfx_mode(GFX_AUTODETECT_WINDOWED, windowWidth, windowHeight, 0, 0); picA = load_bitmap("starfish.pcx", NULL); //Copy the image to the upper-left corner of the // onscreen window. blit(picA, screen, 0,0,0,0,width,height);