I think it's time to learn about the
tile modes, Mode 0 - 2. Tile modes have been around for quite a
while and they can be very useful. You start with a set of tiles,
all of which are 8x8 pixel bitmaps. Then you have a map which is
used to create a background out of those tiles.
For this tutorial, basically what I do is take a bitmap and break
it into tiles and create a map with gfx2gba. These are then used
to recreate the original bitmap. In most modes the screen is 240x160
pixels. This means there are 600 8x8 tiles (600 tiles * 8 pixels
wide * 8 pixels high = 38400 pixels = 240 * 160 pixels). Think about
that for a minute before you move on to make sure you understand
what I mean.
For this tutorial, I've created a picture called paradise.bmp (which
I took on a trip to the Bahamas). Copy the file (or your
own BMP) to the gfx directory.
Change to that directory and type: gfx2gba -fsrc -m -pparadise.pal -t8 paradise.bmp
NOTE: This is different from what we used on Day
4. -t8 means 8 pixel tiles, -m means map
I must stress again that you should take the time to read the Readme that comes with gfx2gba. It's a great program but you have to know what you are doing!
This will create three files: paradise.pal.c paradise.raw.c paradise.map.c
Again, go ahead and take a quick peek at the files. The important
thing about paradise.map.c is the name of the array that is created.
It should be paradise_Map. The array created in paradise.raw.c is paradise_Tiles. You will see these names later in the
tutorial program.
Speaking of which, let's go ahead and display that (tile mode)
background.
// The Main HAM Library
#include <mygba.h>
// Graphics Includes
// Created using:
// gfx2gba -fsrc -m -pparadise.pal -t8 paradise.bmp
#include "gfx/paradise.pal.c"
#include "gfx/paradise.raw.c"
#include "gfx/paradise.map.c"
// Function: main()
int main()
{
// Variables
map_fragment_info_ptr bg_paradise; // BG pointer
// Initialize HAMlib
ham_Init();
// Setup the background mode
ham_SetBgMode(1);
// Initialize the background palette
ham_LoadBGPal((void*)paradise_Palette,256);
// Setup the tileset for our image
ham_bg[0].ti = ham_InitTileSet((void*)paradise_Tiles,
SIZEOF_16BIT(paradise_Tiles),1,1);
// Setup the map for our image
ham_bg[0].mi = ham_InitMapEmptySet(3,0);
bg_paradise = ham_InitMapFragment((void*)paradise_Map,
30,20,0,0,30,20,0);
ham_InsertMapFragment(bg_paradise,0,0,0);
// Display the background
ham_InitBg(0,1,0,0);
// Infinite loop to keep the program running
while(1) {}
return 0;
} // End of main()
Code Explanation
map_fragment_info_ptr bg_paradise;
This data type is used to store all the information about our background.
If you want to know more about it, here's a code snippet from mygba.h. typedef struct map_fragment_info_typ
{
u16* src; // location of this map (usually ROM/EXWRAM)
u16* src_ofs; // location of the data start IN the map
currently set
u8 map_rot; // designates this map to be rotation type
map
u16 map_total_x; // actual map size in tiles / x
u16 map_total_y; // actual map size in tiles / y
u16 map_ofs_x; // offset into maps location start in
tiles / x
u16 map_ofs_y; // offset into maps location start in
tiles / y
u16 map_tiles_x; // actual map size (from offset on)
in tiles / x
u16 map_tiles_y; // actual map size (from offset on)
in tiles / y
u16 map_line_ofs; // offset that needs to be added after
reading 1 line
// of the map to reach next lines map_x
} map_fragment_info,*map_fragment_info_ptr;
ham_SetBgMode(1);
For this example we'll use Mode
1 . In this tile mode the screen is composed of 8x8 pixel squares.
Backgrounds 0, 1, and 2 are available. Background 2 can be rotated
or scaled.
ham_bg[0].ti
= ham_InitTileSet( ... );
This loads our tileset to background 0. It is passed the address
of the tileset, the size of the tiles to be copied in 16 bit chunks,
the color mode, and cbb_only_mode. This last parameter is somewhat
tricky - I recommend you use the default of 1 for now.
ham_InitBg(0,1,0,0);
This will actually draw the background. It is passed the background
number you wish to initialize, whether the background is hidden
or not, the priority of the background, and whether the background
should be mosaic or not. If you have no't setup the .ti and .mi parameters,
this will return an error.
Well, I don't think that was too difficult. Again, mess with the
code and see what you can do before moving on to Day
7.
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Code
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