VGA Fonts: Difference between revisions

== Displaying a character ==

Okay, we have a font bitmap, but how to use it? Here's a simple example:

<source lang="c">

//this is the bitmap font you've loaded

unsigned char *font;

void drawchar(unsigned char c, int x, int y, int fgcolor, int bgcolor)

{

int cx,cy;

int mask[8]={1,2,4,8,16,32,64,128};

unsigned char *gylph=font+(int)c*8*16;

for(cy=0;cy<16;cy++){

for(cx=0;cx<8;cx++){

putpixel(glyph[cy]&mask[cx]?fgcolor:bgcolor,x+cx,y+cy);

}

}

}

</source>

It's not so complicated. You supply the function with arguments:

<pre>

c - the character's ASCII code you want to display

x,y - where to draw

fgcolor - foreground color

bgcolor - background color

</pre>

It could be handly to draw the background as well, because it erase the area under the glyph. But sometimes it could be annoying, so here's a slightly modificated version that's using transparent background:

<source lang="c">

//this is the bitmap font you've loaded

unsigned char *font;

void drawchar_transparent(unsigned char c, int x, int y, int fgcolor)

{

int cx,cy;

int mask[8]={1,2,4,8,16,32,64,128};

unsigned char *gylph=font+(int)c*8*16;

for(cy=0;cy<16;cy++){

for(cx=0;cx<8;cx++){

if(glyph[cy]&mask[cx]) putpixel(fgcolor,x+cx,y+cy);

}

}

}

</source>

As you can see, we only have one fgcolor this time. The putpixel call has a condition, only invoked if the bit in the bitmap is set. If it's clear, nothing will happen, thus makes the background transparent.