A Query about GIMP

[firstaider]

I have just processed some photos using GIMP. The majority I altered the Brightness/Contrast and was able to save them as JPEG. A minority flashed up a message that I would need to "Export" the slide to save it as JPEG couldn't cope with it. The slides were duly exported and came up with a different suffix. I deleted this suffix and replaced it with JPG. It was accepted and the photos seem to be acting like the others with no trouble. Any clues as to what is going on?

Bill

[arith]

Probably opacity. PNG GIf can handle different opacity or transparency jpeg can't. Or it ccould be you just didn't flatten the image which means it can't be saved as is.

[Dave Humphries]

Not that I know GIMP, but on Elements that can also happen if you're still working 16 bit (when it offers .tif) at the time of saving.

However, if you manually pick the jpg option as the file type for saving, it converts to 8 bit as it saves.

Most often it is forgetting to flatten the image (converting from multiple layers to one) as Arith says though!

[arith]

The only GIMP I've got can only handle 8 bit unfortunately; and I'm always getting the message 'can't be saved' because I forget to flatten or the image has transparency.

I have not ever worried about it; export and then check to see if it has been saved properly, mine always have.

[Steve S]

With gimp, if you save the file as .xcf , it will save all the layers so you can go back and make changes if you wish. Then flatten and save a copy for the web.

[Wirefox]

If you are processing from raw you will always get this message when you do the first save. As Steve S says, if you have not flattened the layers you will not be able to save as a jpeg without exporting. If you are using a script to process the image you may not realise that multiple layers have been created.

Steve

[Davey]

There are a few formats that will keep various bits intact. For cross suite purposes tiff might be best because many things support it. Problem is it's not a simple standard since it can act as a container and has a lot of different configurations such as compression and layers option.

Most image software will have no trouble with most tiffs, it supports images in 8bit, 16bit and 24/32bit (ie. transparency or alpha channel) although gimp is limited to 8 as you say), it will store layers, can embed profiles that transparency friendly formats wont, eg. targa and png wont handle cmyk. It is a little on the large side for uncompressed data but it supports lossless compression like lzw and packbits compression. It does support jpeg compression too but that isn't lossless and it just acts as a jpeg container essentially.

[firstaider]

Many thanks to you all. Now I have at least some idea of what is happening.
Bill