Re: Rendering onto background image

[Sven Neumann]

Hi,
> 
> I previously posted a message regarding
> rendering onto a background image and indicated
> that, to blend,  I was using :
> 
> (pen.red( x) + background.red( 1-x)) /x
> 
> where x is the number in the glyph pixmap ( 0-4),
> for each color component
> 
> I am acutally using
> 
> (pen.red( x) + background.red( 4-x)) /x
> 
> and getting results that are not as good as I would
> like ( see attachment for example )
> 

It depends how your image data is stored. Assuming you use
RGB with 8 bit per channel, you will want to use the 
following pseudo-code:

result.red = pen.red * x + background.red (255 - x)               

Please not that the values of x are in the range [0..255].
If you use the smooth renderer, it will be 0,1,2,...,255,
otherwise 0,64,127,195,255. At least that's true for 
freetype2.


Salut, Sven