## ShowAlpha, ShowRed, ShowGreen, ShowBlue

`ShowAlpha` (clip, string pixel_type)
`ShowBlue` (clip, string pixel_type)
`ShowGreen` (clip, string pixel_type)
`ShowRed` (clip, string pixel_type)

`ShowAlpha` shows the alpha channel of a RGB32 clip, available in v2.53. `ShowBlue` / `ShowGreen` / `ShowRed` shows the selected channel of a RGB clip, available in v2.56.

In v2.54 `ShowAlpha` now returns RGB, YUY2, or YV12 via the pixel_type argument. The latter two can be used to layer an RGB clip with alpha transparency data onto a YUV clip using the 3-argument form of `Overlay`, because when setting pixel_type to YUY2 or YV12 the luma range is [0,255].

In v2.56 `ShowAlpha/Red/Green/Blue` now returns RGB24, RGB32, YUY2, or YV12 via the pixel_type argument. For RGB32 output the selected channel is copied to all R, G and B channels, but not the Alpha channel which is left untouched. For YUV output the selected channel is copied to the Luma channel, the chroma channels are set to grey (0x80).

Examples:

    # shows alpha channels of clip
    AviSource("clip.avi")
    ShowAlpha()

    # swaps red and blue channels:
    AviSource("clip.avi")
    MergeRGB(ShowBlue("YV12"), Last, ShowRed("YV12"))

Changelog:

v2.56 | added ShowBlue, ShowGreen and ShowRed

`$Date: 2005/07/08 22:53:16 $`