Episode 141: The Fourth Colour (Microsode 1)

Download the Video! (18.2 MB, 9:35)

This is the first Microsode of Meet the GIMP. This are short(er) videos that are produced ahead of publication and cover one topic – and no chit chat about my life, the site, the forum and so on.

In this Microsode I talk about the fourth value of a pixel, the opacity or transparency. It turns up in layers, tool settings and in the concept of layer masks. The erase tool can erase to the background colour or to transparency. You can even lock the alpha channel of a layer and so keep the transparent parts while painting in the image. BTW, I think I forgot to mention the proper name of the fourth “colour” – alpha. (Edit: I did at 5:00! 🙂 )


00:27 Microsodes
01:25 3 nubers for red, green, blue – and one for opacity / transparency
02:40 opacity in the layer dialogue
02:50 the checkerboard
03:10 opacity in paint tools
04:30 two modes of the erase tool – alpha channel of a layer
05:40 lock opacity
06:20 making straight lines
07:40 layer masks

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Meet the GIMP Video Podcast by Rolf Steinort and Philippe Demartin is licensed under a Creative Commons Attribution-Share Alike 3.0 Germany License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

9 thoughts on “Episode 141: The Fourth Colour (Microsode 1)

  1. Hi Rolf, this short-and-sweet-format is excellent!
    Very memorable information that will be easy to retrieve later.
    I like it (though I wouldn’t like to miss your loosey-goosey talking in Macrosodes 😉

  2. But I miss the older shows in mobile version. There are only shows to 125 and only 133 and then nothing. Which is the reason?
    I love to look the shows with putting my iPod on TV and work with my Notebook.

  3. Thanks a lot for mentioning the 4th color. I myself had to spend a couple of hours trying to think how to “explain” alpha, what was “alpha”? This was a few months ago. Eventually I came up with your same conclusion: it’s nothing but the 4th value of each pixel, a 4th channel that controls opacity. Bingo!

    The mini-chapter feels a bit too rushed, though. For instance, when you erase the layer and white color pops out, that was unexpected! For the advanced eye, it was clear that the eraser used the BG color (white), because the layer didn’t have Alpha channel. But for the novices, this slide can get quite a bit confusing. I would personally recommend to rehearse the Microsodes beforehand, since there is barely any time for correcting real-time errors.

    Last but not least, I would still love to still see some “Macrosodes” (maybe once per month?). The chit-chat is something I always enjoyed from your shows. After all we are here to learn and have a good time, not only to learn!!

    I take this opportunity to thank you a lot for Meet the GIMP. Your lessons and comments have been a very, very, very valuable resource for me. Thanks.


  4. @Xavi: These Microsodes will not be the standard, they will (hopefully) fill the gaps when I have not enough time for making an episode. I have to find out a workflow for them to fit into smaller gaps of my time. For a normal episode I need at least 2 free hours for planning and recording in one block and another such block for editing. Rendering and putting it online needs only small activity and a lot of wainting. 😉

    I think I have put too much information into this Microsode and so it got rushed a bit.

    @GFHardy I asked several times here how to convert the mobile episodes. No answer. 🙁 Now I have encoded them with Handbrake in all possible ways. They will go up in a blog post this afternoon, combined with a poll which version to chose. I don’t own any Apple products since the started to encrypt the interface to keep iTunes the only interface. So I can’t test what is working and what not.

    If there is a clear winner in the poll I’ll include that in the render script and reactivate the feed.

  5. Dear Rolf,
    if I’m able to help you in converting i would do so. But I have no Linux system running. I will change the old Win System into Linux-PC as soon as possible. But actually i work on Mac with a new MacBookpro, and I love it.

    I wonder, because you had in former times always a version, which is running on iPod.
    Why do you change the format? I think, the new format will take only more MB and you can look the shows in the same quality.

    Here an adress who have also an iPod version : http://foto-podcast.de/ = Blende 8.
    And they too: http://www.cczwei.de/ or http://www.swr.de/ratgeber/multimedia
    And so on. I have many video Podcasts and no problems with syncing on my iPod.

    On your vote only version 2 is syncing from iTunes to iPod.

    I hope you will produce such a version, so I can look on TV and work with your ideas on my MacBook.

    Thank You very much!


  6. is it alright if I use some of your posts on my blog and link back to you? i am pagerank 3. thanks!

  7. @rapdishare forum: No it is not, and so I have erased the link in your post.

    And I am Pagerank 6!

    1000x better than you!

    Take that!

    A long way to go…… 😉

  8. Pingback: MTG: Эпизоды 2 квартала 2010 « Блог фотолюбителя :)

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