Available Allegro examples

ex12bit — How to fake a 12-bit truecolor mode on an 8-bit card.
ex3buf — Mode-X triple buffering and retrace interrupt simulation.
ex3d — 3d 'bouncy cubes' demo.
exaccel — Using offscreen video memory to store source graphics for VBE/AF.
exalpha — Creating and using 32 bit RGBA sprites.
exbitmap — Loading and displaying PCX and BMP files.
exblend — Using translucency in truecolor modes.
excamera — Viewing a 3d world from an arbitrary camera position.
excolmap — Creating graphical effects with color mapping tables.
exconfig — Using the configuration routines.
excustom — Creating custom GUI objects.
exdata — Accessing the contents of datafiles.
exdbuf — How to use double buffering to avoid flicker.
exexedat — Appending datafiles onto your executable.
exfixed — Using fixed point maths.
exflame — How to write directly to video memory improving performance.
exflip — Comparison of double buffering and page flipping.
exfont
exgui — Using the GUI routines.
exhello — Simple graphical "hello world" program.
exjoy — Detecting, calibrating and using joystick input.
exkeys — How to get input from the keyboard in different ways.
exlights — One way to do colored lighting effects in a hicolor video mode.
exmem — Drawing onto memory bitmaps and then blitting them to the screen.
exmidi — Playing MIDI music.
exmouse — Getting input from the mouse.
exnew_events
exnewapi
expackf — Using custom PACKFILE vtables.
expal — Palette effects and color cycling.
expat — Using patterned drawing modes and sub-bitmaps.
exquat — A comparison between euler angles and quaternions.
exrgbhsv — RGB <-> HSV colorspace conversions.
exsample — Playing digital samples.
exscale — Loading PCX files and bitmap stretching.
exscn3d — Using the 3d scene functions.
exscroll — Mode-X hardware scrolling and split screens.
exshade — Gouraud shaded sprites.
exspline — Constructing smooth movement paths from spline curves.
exsprite — Datafiles access and sprite animation.
exstars — 3d starfield and lightsourced spaceship.
exstream — Playing audio streams.
exswitch — Controlling the console switch mode for background running.
exsyscur
extimer — Using the timer (delays and interrupts).
extrans — Lighting and translucency effects.
extruec — Truecolor pixel format conversions.
exunicod — Using Unicode string functions.
exupdate — Supporting different screen update methods in a single program.
exxfade — Truecolor image loading and fades.
exzbuf — Z-buffered polygons demo.

With Allegro comes quite a bunch of examples, which go from the simple introductory `Hello world' to more complicated programs featuring truecolor blending effects. This chapter describes these examples which you can find in the allegro/examples folder. You don't have to go through them in the same order as this documentation, but doing so you will learn the basic functions and avoid missing any important bit of information.

Example exhello

This is a very simple program showing how to get into graphics mode and draw text onto the screen.

See also: END_OF_MAIN, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, clear_to_color, desktop_palette, font, install_keyboard, makecol, readkey, release_screen, screen, set_gfx_mode, set_palette, textout_centre_ex.

Example exmem

This program demonstrates the use of memory bitmaps. It creates a small temporary bitmap in memory, draws some circles onto it, and then blits lots of copies of it onto the screen.

See also: BITMAP, END_OF_MAIN, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, blit, circle, clear_bitmap, create_bitmap, desktop_palette, destroy_bitmap, install_keyboard, palette_color, readkey, release_screen, screen, set_gfx_mode, set_palette.

Example expal

This program demonstrates how to manipulate the palette. It draws a set of concentric circles onto the screen and animates them by cycling the palette.

See also: END_OF_MAIN, PALETTE, RGB, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, black_palette, circlefill, install_keyboard, install_mouse, keypressed, release_screen, screen, set_gfx_mode, set_palette, show_mouse.

Example expat

This program demonstrates the use of patterned drawing and sub-bitmaps.

See also: BITMAP, END_OF_MAIN, acquire_bitmap, allegro_error, allegro_init, allegro_message, bitmap_mask_color, blit, clear_to_color, create_bitmap, create_sub_bitmap, desktop_palette, destroy_bitmap, drawing_mode, font, install_keyboard, makecol, masked_blit, palette_color, readkey, rectfill, release_bitmap, screen, set_gfx_mode, set_palette, solid_mode, text_height, text_length, textout_ex.

Example exflame

This program demonstrates how to write directly to video memory. It implements a simple fire effect, first by calling getpixel() and putpixel(), then by accessing video memory directly a byte at a time, and finally using block memory copy operations.

See also: END_OF_MAIN, PALETTE, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, bmp_read_line, bmp_unwrite_line, bmp_write_line, clear_keybuf, font, getpixel, install_keyboard, keypressed, line, makecol, putpixel, release_screen, screen, set_gfx_mode, set_palette, textout_ex.

Example exdbuf

This program demonstrates the use of double buffering. It moves a circle across the screen, first just erasing and redrawing directly to the screen, then with a double buffer.

See also: BITMAP, END_OF_MAIN, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, blit, circlefill, clear_keybuf, clear_to_color, create_bitmap, desktop_palette, destroy_bitmap, font, install_keyboard, install_timer, keypressed, makecol, release_screen, retrace_count, screen, set_gfx_mode, set_palette, textprintf_ex.

Example exflip

This program moves a circle across the screen, first with a double buffer and then using page flips.

See also: BITMAP, END_OF_MAIN, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, circlefill, clear_keybuf, clear_to_color, create_bitmap, create_video_bitmap, desktop_palette, destroy_bitmap, font, install_keyboard, install_timer, keypressed, makecol, retrace_count, screen, set_gfx_mode, set_palette, show_video_bitmap, textprintf_ex.

Example exfixed

This program demonstrates how to use fixed point numbers, which are signed 32-bit integers storing the integer part in the upper 16 bits and the decimal part in the 16 lower bits. This example also uses the unusual approach of communicating with the user exclusively via the allegro_message() function.

See also: END_OF_MAIN, allegro_init, allegro_message, fixdiv, fixed, fixmul, fixsqrt, fixtof, ftofix, itofix.

Example exfont

This is a very simple program showing how to load and manipulate fonts.

See also: END_OF_MAIN, FONT, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, clear_to_color, desktop_palette, destroy_font, extract_font_range, font, install_keyboard, load_font, makecol, merge_fonts, readkey, release_screen, screen, set_gfx_mode, set_palette, textout_centre_ex.

Example exmouse

This program demonstrates how to get mouse input. The first part of the test retrieves the raw mouse input data and displays it on the screen without using any mouse cursor. When you press a key the standard arrow-like mouse cursor appears. You are not restricted to this shape, and a second keypress modifies the cursor to be several concentric colored circles. They are not joined together, so you can still see bits of what's behind when you move the cursor over the printed text message.

See also: BITMAP, END_OF_MAIN, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, bitmap_mask_color, circle, clear_keybuf, clear_to_color, create_bitmap, desktop_palette, destroy_bitmap, font, get_mouse_mickeys, install_keyboard, install_mouse, install_timer, key, keypressed, makecol, mouse_b, mouse_x, mouse_y, mouse_z, palette_color, poll_mouse, readkey, release_screen, screen, set_gfx_mode, set_mouse_sprite, set_mouse_sprite_focus, set_palette, show_mouse, textout_centre_ex, textout_ex, textprintf_centre_ex, textprintf_ex, vsync.

Example extimer

This program demonstrates how to use the timer routines. These can be a bit of a pain, because you have to be sure you lock all the memory that is used inside your interrupt handlers. The first part of the example shows a basic use of timing using the blocking function rest(). The second part shows how to use three timers with different frequencies in a non blocking way.

See also: END_OF_FUNCTION, END_OF_MAIN, LOCK_FUNCTION, LOCK_VARIABLE, SCREEN_W, allegro_error, allegro_init, allegro_message, clear_to_color, desktop_palette, font, install_int, install_int_ex, install_keyboard, install_timer, key, keypressed, makecol, readkey, rest, screen, set_gfx_mode, set_palette, textprintf_centre_ex.

Example exkeys

This program demonstrates how to access the keyboard. The first part shows the basic use of readkey(). The second part shows how to extract the ASCII value. Next come the scancodes. The fourth test detects modifier keys like alt or shift. The fifth test requires some focus to be passed. The final step shows how to use the global key array to read simultaneous keypresses. The last method to detect key presses are keyboard callbacks. This is demonstrated by by installing a keyboard callback, which marks all pressed keys by drawing to a grid.

See also: END_OF_FUNCTION, END_OF_MAIN, LOCK_FUNCTION, SCREEN_H, SCREEN_W, acquire_screen, allegro_error, allegro_init, allegro_message, blit, clear_keybuf, clear_to_color, desktop_palette, font, install_keyboard, install_timer, key, key_shifts, keyboard_lowlevel_callback, keypressed, makecol, readkey, rectfill, release_screen, rest, scancode_to_name, screen, set_gfx_mode, set_palette, textprintf_centre_ex, textprintf_ex, ureadkey, usprintf, ustrzncpy.

Example exjoy

This program uses the Allegro library to detect and read the value of a joystick. The output of the program is a small target sight on the screen which you can move. At the same time the program will tell you what you are doing with the joystick (moving or firing).

See also: BITMAP, END_OF_MAIN, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, calibrate_joystick, calibrate_joystick_name, circle, clear_bitmap, clear_keybuf, create_bitmap, default_palette, destroy_bitmap, drawing_mode, font, install_joystick, install_keyboard, joy, key, keypressed, num_joysticks, palette_color, poll_joystick, putpixel, readkey, screen, set_gfx_mode, set_palette, textout_centre_ex, textprintf_centre_ex, textprintf_ex.

Example exsample

This program demonstrates how to play samples. You have to use this example from the commandline to specify as first parameter a WAV or VOC sound file to play. If the file is loaded successfully, the sound will be played in an infinite loop. While it is being played, you can use the left and right arrow keys to modify the panning of the sound. You can also use the up and down arrow keys to modify the pitch.

See also: END_OF_MAIN, SAMPLE, SCREEN_H, SCREEN_W, adjust_sample, allegro_error, allegro_init, allegro_message, clear_to_color, desktop_palette, destroy_sample, font, install_keyboard, install_sound, install_timer, key, load_sample, makecol, play_sample, poll_keyboard, rest, screen, set_gfx_mode, set_palette, textprintf_centre_ex.

Example exmidi

This program demonstrates how to play MIDI files.

See also: END_OF_MAIN, MIDI, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, clear_to_color, desktop_palette, destroy_midi, font, get_filename, get_midi_length, install_keyboard, install_sound, install_timer, key, keypressed, load_midi, makecol, midi_pause, midi_pos, midi_resume, midi_time, play_midi, readkey, rectfill, rest, screen, set_display_switch_mode, set_gfx_mode, set_palette, text_height, text_length, textprintf_centre_ex.

Example exgui

This program demonstrates how to use the GUI routines. From the simple dialog controls that display a text or a bitmap to more complex multiple choice selection lists, Allegro provides a framework which can be customised to suit your needs.

See also: DATAFILE, DIALOG, END_OF_MAIN, MENU, active_menu, alert, allegro_error, allegro_init, allegro_message, d_bitmap_proc, d_box_proc, d_button_proc, d_check_proc, d_clear_proc, d_ctext_proc, d_edit_proc, d_icon_proc, d_keyboard_proc, d_list_proc, d_menu_proc, d_radio_proc, d_rtext_proc, d_shadow_box_proc, d_slider_proc, d_text_list_proc, d_text_proc, d_textbox_proc, d_yield_proc, do_dialog, gui_bg_color, gui_fg_color, gui_mg_color, install_keyboard, install_mouse, install_timer, key, load_datafile, makecol, position_dialog, replace_filename, screen, set_dialog_color, set_gfx_mode, set_palette, unload_datafile, ustrtok, ustrzcat, ustrzcpy, uszprintf.

Example excustom

A follow up of the exgui.c example showing how to customise the default Allegro framework. In this case a dialog procedure animates a graphical clock without disrupting other GUI dialogs. A more simple option shows how to dynamically change the font used by all GUI elements.

See also: BITMAP, DATAFILE, DIALOG, END_OF_MAIN, FONT, allegro_error, allegro_init, allegro_message, blit, circle, circlefill, clear_to_color, create_bitmap, d_button_proc, d_check_proc, d_clear_proc, d_edit_proc, desktop_palette, destroy_bitmap, do_dialog, fixcos, fixed, fixmul, fixsin, fixtoi, font, install_keyboard, install_mouse, install_timer, itofix, key, line, load_datafile, makecol, object_message, replace_filename, screen, set_gfx_mode, set_palette, unload_datafile.

Example exunicod

This program demonstrates the use of the 16-bit Unicode text encoding format with Allegro. The example displays a message translated to different languages scrolling on the screen using an external font containing the required characters to display those messages.

Note how the Allegro unicode string functions resemble the functions you can find in the standard C library, only these handle Unicode on all platforms.

See also: BITMAP, DATAFILE, END_OF_MAIN, FONT, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, clear_to_color, create_bitmap, font, install_int_ex, install_keyboard, install_timer, keypressed, load_datafile, replace_filename, rest, screen, set_gfx_mode, set_uformat, set_window_title, text_height, text_length, textout_ex, uconvert_ascii, unload_datafile, ustrcat, ustrcpy, ustrsize, ustrsizez.

Example exbitmap

This program demonstrates how to load and display a bitmap file. You have to use this example from the commandline to specify as first parameter a graphic file in one of Allegro's supported formats. If the file is loaded successfully, it will be displayed until you press a key.

See also: BITMAP, END_OF_MAIN, PALETTE, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, destroy_bitmap, install_keyboard, load_bitmap, readkey, screen, set_gfx_mode, set_palette.

Example exscale

This example demonstrates how to use pcx files, palettes and stretch blits. It loads a pcx file, sets its palette and does some random stretch_blits. Don't worry - it's VERY slowed down using vsync().

See also: BITMAP, END_OF_MAIN, PALETTE, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, destroy_bitmap, install_keyboard, keypressed, load_pcx, replace_filename, screen, set_gfx_mode, set_palette, stretch_blit, vsync.

Example exconfig

This is a very simple program showing how to use the allegro config (ini file) routines. A first look at the example shows nothing more than a static graphic and the wait for a keypress. However, the way this graphic is displayed is configured through a custom exconfig.ini file which is loaded manually. From this file the example obtains parameters like fullscreen/windowed mode, a specific graphic resolution to set up, which graphic to show, how to blit it on the screen, etc.

See also: BITMAP, END_OF_MAIN, RGB, SCREEN_H, SCREEN_W, allegro_init, allegro_message, blit, clear_bitmap, font, get_config_argv, get_config_int, get_config_string, install_keyboard, line, load_bitmap, makecol, pop_config_state, push_config_state, readkey, screen, set_color_depth, set_config_file, set_gfx_mode, set_palette, stretch_blit, textout_centre_ex, textprintf_centre_ex, ustrdup, ustricmp.

Example exdata

This program demonstrates how to access the contents of an Allegro datafile (created by the grabber utility). The example loads the file `example.dat', then blits a bitmap and shows a font, both from this datafile.

See also: DATAFILE, END_OF_MAIN, allegro_error, allegro_init, allegro_message, blit, font, install_keyboard, load_datafile, makecol, readkey, replace_filename, screen, set_color_conversion, set_gfx_mode, set_palette, textout_ex, unload_datafile.

Example exsprite

This example demonstrates how to use datafiles, various sprite drawing routines and flicker-free animation.

Why is the animate() routine coded in that way? As you probably know, VIDEO RAM is much slower than "normal" RAM, so it's advisable to reduce VRAM blits to a minimum. Drawing sprite on the screen (meaning in VRAM) and then clearing a background for it is not very fast. This example uses a different method which is much faster, but require a bit more memory.

First the buffer is cleared (it's a normal BITMAP), then the sprite is drawn on it, and when the drawing is finished this buffer is copied directly to the screen. So the end result is that there is a single VRAM blit instead of blitting/clearing the background and drawing a sprite on it. It's a good method even when you have to restore the background. And of course, it completely removes any flickering effect.

When one uses a big (ie. 800x600 background) and draws something on it, it's wise to use a copy of background somewhere in memory and restore background using this "virtual background". When blitting from VRAM in SVGA modes, it's probably, that drawing routines have to switch banks on video card. I think, I don't have to remind how slow is it.

Note that on modern systems, the above isn't true anymore, and you usually get the best performance by caching all your animations in video ram and doing only VRAM->VRAM blits, so there is no more RAM->VRAM transfer at all anymore. And usually, such transfers can run in parallel on the graphics card's processor as well, costing virtually no main cpu time at all. See the exaccel example for an example of this.

See also: BITMAP, DATAFILE, END_OF_FUNCTION, END_OF_MAIN, LOCK_FUNCTION, LOCK_VARIABLE, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, circle, clear_bitmap, clear_keybuf, create_bitmap, destroy_bitmap, draw_sprite, draw_sprite_h_flip, draw_sprite_v_flip, draw_sprite_vh_flip, fixed, font, hline, install_int_ex, install_keyboard, install_sound, install_timer, itofix, key, keypressed, load_datafile, makecol, palette_color, pivot_sprite, pivot_sprite_v_flip, play_sample, rectfill, replace_filename, rest, screen, set_gfx_mode, set_palette, text_height, textout_centre_ex, unload_datafile, vsync.

Example exexedat

This program demonstrates how to access the contents of an Allegro datafile (created by the grabber utility) linked to the exe by the exedat tool. It is basically the exdata example with minor modifications.

You may ask: how do you compile, append and exec your program?

Answer: like this...

1) Compile your program like normal. Use the magic filenames with '#' to load your data where needed.

2) Once you compressed your program, run "exedat foo.exe data.dat"

3) Finally run your program.

Note that appending data to the end of binaries may not be portable accross all platforms supported by Allegro.

See also: DATAFILE, END_OF_MAIN, allegro_error, allegro_init, allegro_message, blit, font, install_keyboard, line, load_datafile, makecol, readkey, screen, set_color_conversion, set_gfx_mode, set_palette, textout_ex, unload_datafile.

Example extrans

This program demonstrates how to use the lighting and translucency functions. The first part of the example will show a dark screen iluminated by a spotlight you can move with your mouse. After a keypress the example shows the full bitmap and the spotlight changes to be a reduced version of the background with 50% of translucency.

The translucency effect is easy to do in all color depths. However, the lighting effect has to be performed in a different way depending on whether the screen is in 8bit mode or another color depth. This is because additive drawing mode uses a different set of routines for truecolor modes.

See also: BITMAP, COLOR_MAP, END_OF_MAIN, PALETTE, RGB, RGB_MAP, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, bitmap_color_depth, blit, circlefill, clear_bitmap, clear_keybuf, color_map, create_bitmap, create_bitmap_ex, create_light_table, create_rgb_table, create_trans_table, destroy_bitmap, draw_trans_sprite, drawing_mode, install_keyboard, install_mouse, install_timer, keypressed, load_bitmap, mouse_x, mouse_y, poll_mouse, rectfill, replace_filename, rest, rgb_map, screen, set_alpha_blender, set_gfx_mode, set_palette, set_trans_blender, set_write_alpha_blender, stretch_blit.

Example extruec

This program shows how to specify colors in the various different truecolor pixel formats. The example shows the same screen (a few text lines and three coloured gradients) in all the color depth modes supported by your video card. The more color depth you have, the less banding you will see in the gradients.

See also: END_OF_MAIN, PALETTE, RGB, SCREEN_H, SCREEN_W, acquire_screen, allegro_init, clear_to_color, font, generate_332_palette, install_keyboard, key, makecol, readkey, release_screen, screen, set_color_depth, set_gfx_mode, set_palette, textout_centre_ex, textout_ex, textprintf_ex, vline.

Example excolmap

This program demonstrates how to create custom graphic effects with the create_color_table function. Allegro drawing routines are affected by any color table you might have set up. In the first part of this example, a greyscale color table is set. The result is that a simple rectfill call, instead of drawing a rectangle with color zero, uses the already drawn pixels to determine the pixel to be drawn (read the comment of return_grey_color() for a precise description of the algorithm). In the second part of the test, the color table is changed to be an inverse table, meaning that any pixel drawn will be shown as its color values had been inverted.

See also: BITMAP, COLOR_MAP, END_OF_MAIN, PALETTE, RGB, RGB_MAP, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, circlefill, clear_keybuf, color_map, create_bitmap, create_color_table, create_rgb_table, destroy_bitmap, drawing_mode, font, generate_332_palette, install_keyboard, keypressed, makecol, rectfill, rgb_map, screen, set_gfx_mode, set_palette, textout_centre_ex, vsync.

Example exrgbhsv

This program shows how to convert colors between the different color-space representations. The central area of the screen will display the current color. On the top left corner of the screen, three sliders allow you to modify the red, green and blue value of the color. On the bottom right corner of the screen, three sliders allow you to modify the hue, saturation and value of the color. The color bars beneath the sliders show what the resulting color will look like when the slider is dragged to that position.

Additionally this example also shows how to "inherit" the behaviour of a GUI object and extend it, here used to create the sliders.

See also: BITMAP, DIALOG, END_OF_MAIN, PALETTE, RGB, RGB_MAP, allegro_error, allegro_init, allegro_message, clear_to_color, create_bitmap_ex, create_rgb_table, d_bitmap_proc, d_box_proc, d_slider_proc, d_text_proc, destroy_bitmap, do_dialog, font, generate_332_palette, get_color_depth, hsv_to_rgb, install_keyboard, install_mouse, install_timer, key, makecol, makecol32, makecol8, object_message, rgb_map, rgb_to_hsv, screen, set_color, set_color_depth, set_gfx_mode, set_palette, textout_ex, vline, vsync.

Example exshade

This program demonstrates how to draw gouraud shaded (lit) sprites. In an apparently black screen, a planet like sprite is drawn close to the middle of the screen. In a similar way to how the first test of extrans works, you move the cursor on the screen with the mouse. Attached to this mouse you can imagine a virtual spotlight illuminating the scene around. Depending on where the mouse is, the goraud shaded sprite will show the direction of the light.

See also: BITMAP, COLOR_MAP, END_OF_MAIN, PALETTE, RGB, RGB_MAP, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, clear_bitmap, color_map, create_bitmap, create_light_table, create_rgb_table, destroy_bitmap, draw_gouraud_sprite, font, install_keyboard, install_mouse, keypressed, line, load_bitmap, mouse_x, mouse_y, palette_color, poll_mouse, replace_filename, rgb_map, screen, set_gfx_mode, set_palette, set_trans_blender, show_mouse, textout_ex.

Example exblend

This program demonstrates how to use the translucency functions in truecolor video modes. Two image files are loaded from disk and displayed moving slowly around the screen. One of the images will be tinted to different colors. The other image will be faded out with a varying alpha strength, and drawn on top of the other image.

See also: BITMAP, END_OF_MAIN, PALETTE, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, circle, clear_bitmap, clear_keybuf, create_bitmap, destroy_bitmap, draw_lit_sprite, draw_trans_sprite, fixcos, fixsin, fixtoi, font, install_keyboard, install_timer, itofix, keypressed, load_bitmap, makecol, replace_filename, retrace_count, screen, set_color_conversion, set_color_depth, set_gfx_mode, set_trans_blender, textprintf_ex, vsync.

Example exxfade

This program demonstrates how to load and display bitmap files in truecolor video modes, and how to crossfade between them. You have to use this example from the commandline to specify as parameters a number of graphic files. Use at least two files to see the graphical effect. The example will crossfade from one image to another with each keypress until you press the ESC key.

See also: BITMAP, END_OF_MAIN, PALETTE, SCREEN_H, SCREEN_W, allegro_error, allegro_exit, allegro_init, allegro_message, blit, create_bitmap, destroy_bitmap, draw_trans_sprite, install_keyboard, keypressed, line, load_bitmap, readkey, screen, set_color_conversion, set_color_depth, set_gfx_mode, set_palette, set_trans_blender, vsync.

Example exalpha

This program demonstrates how to use the 32 bit RGBA translucency functions to store an alpha channel along with a bitmap graphic. Two images are loaded from disk. One will be used for the background and the other as a sprite. The example generates an alpha channel for the sprite image, composing the 32 bit RGBA bitmap during runtime, and draws it at the position of the mouse cursor.

See also: BITMAP, END_OF_MAIN, SCREEN_H, SCREEN_W, allegro_error, allegro_init, allegro_message, blit, clear_keybuf, create_bitmap, destroy_bitmap, draw_trans_sprite, drawing_mode, font, getb, getg, getpixel, getr, install_keyboard, install_mouse, install_timer, keypressed, load_bitmap, makecol, mouse_x, mouse_y, putpixel, rectfill, replace_filename, screen, set_alpha_blender, set_color_conversion, set_color_depth, set_gfx_mode, set_multiply_blender, set_write_alpha_blender, solid_mode, stretch_blit, textprintf_ex.

Example exlights

This program shows one way to implement colored lighting effects in a hicolor video mode. Warning: it is not for the faint of heart! This is by no means the simplest or easiest to understand method, I just thought it was a cool concept that would be worth demonstrating.

The basic approach is to select a 15 or 16 bit screen mode, but then draw onto 24 bit memory bitmaps. Since we only need the bottom 5 bits of each 8 bit color in order to store 15 bit data within a 24 bit location, we can fit a light level into the top 3 bits. The tricky bit is that these aren't actually 24 bit images at all: they are implemented as 8 bit memory bitmaps, and we just store the red level in one pixel, green in the next, and blue in the next, making the total image be three times wider than we really wanted. This allows us to use all the normal 256 color graphics routines for drawing onto our memory surfaces, most importantly the lookup table translucency, which can be used to combine the low 5 bits of color and the top 3 bits of light in a single drawing operation. Some trickery is needed