[fpc-devel] Correlation between TFPColor and RGB values (possible inconsistencies)

[Luiz Americo Pereira Camara]

Mattias Gaertner escreveu:
> On Wed, 17 Feb 2010 06:52:25 -0300
> Luiz Americo Pereira Camara <luizmed at oi.com.br> wrote:
>   
>>
>> fpimage is not documented at all AFAIK.
>>
>> It's not loosing bits if your information, in previous mail, about 
>> TFPColor format is correct.
>>
>> Defining colGray, and related, as TFPColor = (Red: $8080; Green: $8080; 
>> Blue: $8080; Alpha: alphaOpaque) would make it work.
>>     
>
> ... would make it work with a 24bit color image that uses one pixel
> color conversion *$101, div $100.
> It won't work on a 24bit color image that uses color conversion *$100,
> div $100 or on any other format.
>   

Are you saying that TFPColor is just a container for any 48bit format 
and has not a defined format?

>  
>   
>> The point is that the TFPColor constants are inconsistently defined.
>>     
>
> $8000 is exactly the middle. It is the right value for gray.

OK.

If i understand correctly, you are saying that in TFPColor format  $0000 
means black (no color in the channel) $FFFF means white (full color in 
the channel) and between them you get the remaining intensity.

Assuming that, giving a color in 24bit RGB (one byte per channel) where 
$00 means no color $FF full color, if a channel is on the middle ($80 = 
128) it would be equivalent to $8000 in the 48bit format, right? 
LazIntfImage is returning $8080.

If channel is $40 (=64) in 24bit, it should not map to $4000 in 48bit?  
LazIntfImage is returning $4040
If channel is $2 (=2) in 24bit, it should not map to $0200 in 48bit? 
LazIntfImage is returning $2020
If channel is $1 (=1) in 24bit, it should not map to $0100 in 48bit? 
LazIntfImage is returning $1010

AFAIK, it should not be difficult to fix that (assuming is broken).

All in all, this is not an issue for me and i won't take any longer if 
other agree that there's nothing broken.

Luiz