class base_image

The base_image class is the core behind all sprite-types introduced in GALVADERS.
Once you grasp how to work with this class, you know the concept of how GALVADERS is built.

How to work with this class:

First construct a base_image object with: RLE_SPRITE **dt This is RLE_SPRITE * vector (see create_game_params() about how create this vector from Allegro DATAFILE). This pointer should be valid at all time.

BITMAP *dst This is the dest-BITMAP where you want to write sprite-output.
This should be your back-ground buffer.

pos_x,pos_y The sprite location on dest-BITMAP.

z_order This is the Z-Order value for the sprite. Some games don't use this.

sprite_index This is the index of the sprite-image. Thus, dt[sprite_index] gives the sprite address.

bg_flag When this flag is set, the base_image object retains sprite's background when removing it from dest-BITMAP. When clear, a black rectangle is drawn.

Once constructed a base_image object the way of work is simple, just issue a remove() , action() and draw() for each and every frame.

base_image::remove() removes RLE_SPRITE from dest-BITMAP. draw() write RLE_SPRITE to dest-BITMAP.

The virtual method action() does nothing , once you derive your own sprite-class from base_image add all the game-logic code for your object in the action() method.

Thus, having all kinds of objects derived from base_image construct an STL-list or vector of base_image *
, and for each an every frame the remove() , action() and draw() are committed. Since action() is virtual, the right action-method would be called for each object type.

Do a reverse-scan of the list when doing the remove() section, and forward-scan for action() and draw() This keep your dest-BITMAP clean from trails of moving objects.

Take a look at base_image.h for available base_Image methods. I think all of them are straight forward.
Read the code in base_image.cpp for better understanding, it's simple.

To make things easy, this page will be updated later.

There is another base_image class, not used in GALVADERS, that works directly with Allegro DATAFILE array. This one does not require RLE_SPRITE vector-pointer, but a DATAFILE pointer instead. The DATAFILE pointer should be valid all time.