Randy Thanks for your comments - it's reassuring to know that others have similar woes ;)
> I've had some similar problems with gamma when savings images with > Save Image... as you did, and also with some other dataflows > (e.g. ReadImage/Overlay/WriteImage). > > Up-front, I'll tell you I don't fully understand how/where/when DX > applies gamma. Hopefully someone that knows will speak up. But... > > This may be related to what you're seeing: > > ./dx-4.2.0/src/exec/libdx/displayfb.c: _dxfinit_convert(1.5); > /* gamma=1.5 is suitable for frame buffer */ > > Could be that a 1.5 gamma is always applied for display, but not for > saving images via Magick, which would explain your results. > interesting... I've played around with the DXGAMMA environment variable and this definitely works fine for the screen display i.e. it overrides the default setting (which I thought was 2.0 rather than 1.5). When saving an image however, it seems you must use the gamma setting box in the save image menu which makes sense. Setting DXGAMMA to 1.5 produces images which are a little darker but do not have the sharp contrasts I'm getting via ImageMagick so I think that the effective gamma setting used by ImageMagick is probably not 1.5. I have no experience programming with ImageMagick - would it be possible to get it to read say, the DXGAMMA environment variable? I know that you can specify a gamma as an argument to the convert utility that comes with ImageMagick. Presumably the ImageMagick API also allows this. Of course it's easy to correct a lot of this manually - my main problem is with JavaDX, which in 4.2 is producing very dark, high contrast images on my web pages (although they are just about acceptable) - the brute force solution is to switch back to the 4.1 JavaDX server which is no great problem. Thanks again for your help, I'll delve into this a little deeper. Jerry -------------------------- Jerry Hagon School of Natural Sciences Newcastle University UK
