[E-devel] Problem with Imlib2 and Alpha TIFs

[Simon W. <si...@th...>]

I've started noticing a problem with tiffs that have alpha channels - I
converted the alpha.tif image to alpha.jpg using Imlib2 (both 1.0.6 and
1.1.0). Loading the tif up in xv (or Shake or The Gimp) I get the
correct brightness but if I convert it with Imlib2 (using the really
basic conversion eaxample in the docs) the resulting image (in this case
alpha.jpg) is too dark. 

This is also the case if save out as png or gif so it's not, as far as I 
can tell, a problem with the jpg output.

I noticed in save() that there's a prescaling by an alpha factor but no 
corresponding descaling in raster() (presumably it's in the TIffGetR 
macros) but unless I'm smoking crack that would result in the imaeg 
being too bright so basically I'm stumped.

I did notice that the alpha on each pixel was 146 and that if I 
multiplied r,g and b by 1.46 then the brightness was almost right. 
That's nothing more than a fudge factor though - arbitary numbers a go 
go.

Any ideas? Am I ignoring something in my conversion code?

Simon