Comments on: Choosing a Different Transparency Alpha Channel for an Image

By: Jongware

Jongware — Mon, 10 Aug 2009 13:43:41 +0000

The scripting Object Model allows access to the other channels. It seems the Show PDF options javascript uses this, but only for PDFs!

It should be possible to write a small(ish) javascript that allows you to select any of the channels for a selected image.

This simple command

alert (app.selection[0].images[0].clippingPath.alphaChannelPathNames.join(‘\r’));

shows the channels in a selected image — if I only could find a way to change it here … (Just setting another name doesn’t work.)

By: Jerome

Jerome — Sun, 09 Aug 2009 20:42:45 +0000

No, it is just something that we experienced at work with images that had one or more alpha channels. I don’t know if it always happened and I think it was noticeable mostly in the print-out. I believe Quark reacted in a similar fashion. The fix was just to delete the extra channels. As I recall it happened with tiffs and psd files.

By: David Blatner

David Blatner — Sun, 09 Aug 2009 18:12:38 +0000

@Jerome: I have never experienced that. Can you point us to any tech note or confirmed bug on that?

By: Jerome

Jerome — Sun, 09 Aug 2009 15:09:23 +0000

As I recall Alpha channels can cause problems with placed graphics. I have seen it where ID combines all the alpha channels on import as a mask, which can cause some confusion when someone else if placing the images. It could be that explicitly naming the alpha channel fixes this, I never used them in final files instead going with PSD files with layer transparency.

By: liviu

liviu — Sun, 09 Aug 2009 13:41:06 +0000

It would have been useful a button to choose the options you have when you place an image. It is a mess if I want to drag and drop an image because indesign doesn’t ask me anything about alpha channels… I dont really like the relink thing… It seems to be the only option for now…

By: David Blatner

David Blatner — Sat, 08 Aug 2009 03:48:54 +0000

@Branislav: Yes, the relink thing is useful for a number of things. For PDF, however, you can use this free script which lets you re-open import options. Nifty. @Sean: There's nothing wrong with just using a normal transparent background. That works great... unless you have several different channels from which you want to choose. Having multiple channels is like keeping your options open!

By: Sean Hosley

Sean Hosley — Fri, 07 Aug 2009 22:34:10 +0000

Is there an issue with just using a PSD or TIF image with a transparent background (as opposed to an alpha)?

The only time I really ever use alpha channels is when I’m making graphics for video.

Should I rethink the way I’m doing things?

By: Branislav Milic

Branislav Milic — Fri, 07 Aug 2009 21:18:45 +0000

It’s true that going to Object > Clipping Path > Options does not help has it does not provide the smooth effect.

BTW, the issue that you raise here is the same for imported PDFs…