QTR-Quadtone RIP

On Wednesday, September 6, 2006, at 03:25  PM, Ernst Dinkla wrote:

> Roy Harrington wrote:
>
>>
>> The only way to understand all this is break everything into 
>> individual
>> steps and
>> understanding what each does.
>
> Roy,
>
> One way to get some grip on this is by getting the knowledge
> how QTR does the RGB to Grayscale conversion.

Well, that's easy.   For a gray RGB file i.e. R=G=B, the grayscale 
values are the same as R, G, or B.
When it's actually a color image fixed weightings are used:

     Gray = .31*R + .61*G + .08*B

> Given the print results I get it must be compatible to Qimage

Qimage never does RGB to Grayscale, but Grayscale to RGB in the absence 
of profiles & CM (Ptr ICC Off)
I think it does R=G=B = Gray,  so I guess that's compatible.   In 
general these probably would be
the non-CM conversions for any non-ICC product.

All CM conversions will preserve L values as much as possible.  The 
difficulties are where K=100 is not L=0,
then BPC etc can give various results.

Roy

> conversions and of the last I see no difference in PWP and
> TIFFconvert. I think it goes all back to the same mapping
> table when CM isn't used.
>
> Ernst
> -- 
>
>                     --
>            Ernst Dinkla
>
-
Roy Harrington
roy@...
Black & White Photo Gallery
http://www.harrington.com