Re: Convert RGBA to BGRA using standard library?

On Sat, May 28, 2011 at 5:55 AM, Greg Ewing <greg.ewing-F+z8Qja7x9Xokq/[email protected]>wrote:

> Can anyone think of an efficient way to convert a string
> full of RGBA image data to BGRA, using only what's available
> in the standard library?
>
> I'm trying to add a function to PyGUI for creating an Image
> object from arbitrary data. The problem I'm having is that
> GDI+ on Windows expects BGRA, whereas most other platforms
> deal with RGBA. I don't want to require the user to supply
> the data in different formats on different platforms, so
> PyGUI needs to be able to convert where necessary.
>
> I know the conversion can be done easily using something
> like PIL or numpy, but I'm after a solution that doesn't
> depend on any third-party libraries.
>
> --
> Greg
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>


Greg, I had to solve this problem in another application and ended up using
the array module and the with the slice syntax.

import array

input = "rgbaRGBA1234"
ba = array.array('c', input)
ba[0::4], ba[2::4] = ba[2::4], ba[0::4]

print ba.tostring()

>> bgraBGRA3214

It is fairly fast too.

Good luck and keep up the great work.