Re: alphatype to stills in FCP XMLs
Re: alphatype to stills in FCP XMLs
- Subject: Re: alphatype to stills in FCP XMLs
- From: Paul Schneider <email@hidden>
- Date: Fri, 9 Apr 2010 11:49:12 -0500
Hi all,
It sounds like FCP should guess the alpha if it isn't specified in the XML - please file a bug.
In the meantime, if you want to get the alpha information programmatically in your own code, you might look into using CGImageGetAlphaInfo. This will tell you the alpha state of any image that CoreGraphics knows how to read, which is most popular formats.
The problem with parsing the file format for its premult state is that often this information is missing or, worse, incorrect. I'm not sure if CoreGraphics attempts to "guess" the alpha state of unlabeled images. If you want to do this yourself, you can examine the pixels in the image. If any pixel has a color component greater than its alpha component, the image can NOT be premultBlack. And if any pixel has a color component less than the inverse of its alpha component (255 - alpha), the image can NOT be premultWhite. With this information, you should be able to make a reasonable guess.
- Paul
On Apr 8, 2010, at 2:42 PM, Rainer Standke wrote:
> Hello,
>
> I am working on something that imports stills into FCP via XML. These stills are exclusively tga's for now. It turns out that FCP seems to know a couple of different alpha types: none, straight, black, or white. Straight is most likely not pre-multplied, black is probably pre-multiplied black, and white is premultiplied white. I have seen FCP guess both black and white for tga's, and the FCP user manual says:
>
> "When you import a still image file, Final Cut Pro identifies the type of alpha channel and sets the imported clip’s Alpha property appropriately."
>
> Only in the case of an XML import it doesn't guess, even if the alphatype tag is omitted.
>
> Is there any way to have FCP guess upon XML import the same way that it does when the user simply drags a file into the project?
>
> Or, how can I find out programmatically if the the alpha is premultiplied?
>
> Thanks,
>
> Rainer Standke _______________________________________________
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