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Thread: Mentor request for gif redraw

  1. #1

    Post Mentor request for gif redraw

    Can someone mentor me through a project, please?

    I've found an animated gif that I like, but I want to use Gimp to recolour it - ideally, I'd like to effectively redraw/reconstruct it (beyond the copyright line) but when I try to use the colour menu, most of the options tell me "XXX operates only on RGB colour layers."

    I tried saving the gif as a xcf in the hope that that would make the colours available, but it doesn't. I even tried painting over it, but the colours are wrong when I paint (like I choose bright red and the brush paints brown).

    As you can see, I haven't a clue what I'm doing and I'd appreciate it if someone could 'teach a man to fish' on this project. Hopefully (no guarantees) I'll only need a nudge in the right direction every now and then, rather than a step-by-step tutorial, but at the moment I can't even get started.

    Any volunteers?
    Mapping a Traveller ATU.

    See my (fantasy-based) apprenticeship blog at:

    http://www.viewing.ltd.uk/cgi-bin/vi...forums&sx=1024

    Look for Chit Chat, Sandmann's blog. Enjoy.

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  3. #3
    Guild Artisan töff's Avatar
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    I dunno about GIMP ...

    A lot of filters only work on RGB or some specific color mode.
    If you can access each frame of the GIF, you can convert to RGB and apply your filter individually.

    You can then take all the frames and recompile them in to an animated GIF using one of the bazillion Gif utils out there. On recompile, the colors will be reintegrated into a new index.

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    Administrator RobA's Avatar
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    Quote Originally Posted by töff View Post
    I dunno about GIMP ...

    A lot of filters only work on RGB or some specific color mode.
    If you can access each frame of the GIF, you can convert to RGB and apply your filter individually.
    In GIMP, it is Image->Mode->RGB.

    To change specific colours you can play with Colours->Hue Saturation or Colurs->Map->Rotate Colours

    You will have to re-dither/quantify down to 256 colours again. The biggest problem with GIF animations is ensuring each frame has the same dither pattern or you will inadvertently end up with glitter.

    -Rob A>

  5. #5
    Software Dev/Rep Redrobes's Avatar
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    You could have another quick run through my tech tut. In there it explains a little about formats. Specifically in this case all GIF type images are paletted to a maximum of 256 colours so when you have a GIF anim you can extract all the frames from it but they will all be up to 256 colours. To do special processing on images you normally need full color or true color mode which is a byte per pixel or 24 bit or 16 million colours.

    You can upsample the colours in the frames from 8 to 24 bit but out of the range of possible 16 million it will still use 256 of them until you start to blur or do some processing. The issue is that once all finished you will probably want to get it back into a GIF again and then you must down sample the colours from 24 bits back 8 again.

    There's not a lot of options tho. The not completely new browsers don't support animated PNG format - the MNG format which does do RGBA animations and whilst firefox, opera etc will support that as does windows picture and fax viewer, I was not sure about IE. Last time I tried it didn't but I cant see why it should not now.

    Incidentally ImageMagick will generate MNG files from a series of PNGs if you want to try.

  6. #6
    Guild Artisan töff's Avatar
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    If you use one of those gif compilers, you don't have to worry about the index color. They take care of that for you.

  7. #7
    Software Dev/Rep Redrobes's Avatar
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    I dunno if this is gonna work but here is a gif next to an mng so whether any of us will be able to see it will be interesting. I am not getting life out of firefox or IE or windows pic viewer but (as usual) irfan view is alright with them.

    1st: GIF


    2nd: MNG


    Right, lets see what this does. I expect we will see the gif only...

    Links to files:
    http://www.viewing.ltd.uk/Temp/CG/Ge..._Test/anim.gif
    http://www.viewing.ltd.uk/Temp/CG/Ge..._Test/anim.mng

  8. #8
    Guild Artisan töff's Avatar
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    Yeh, I only see the GIF. I'm on Firefox 3.5.3.

    I'd never heard of the MNG. I was just checking out its site. Cool! About time for a multibit-alpha animated format. It's like Ping and Gif had a love child ... Piff.

  9. #9
    Software Dev/Rep Redrobes's Avatar
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    Yeah, unfortunately its been about for a while and its not really took off well. I think with the full color pixels then there is very little match between similar but not exactly the same frames so it practically has to encode them all as full PNGs. This is unlike say MJPEG which compresses across the series in time as well as X-Y and because JPG is lossy then it can munge it in 3 dimensions and compresses it a lot better. Still, it looks like Opera also does not see it so I think all three big gun browsers on windows at least cant do it. God help up if Safari see it fine - we'll never hear the end of it... So yeah its potentially cool but in reality its not gonna happen. Shame cos I could point out the great quality difference between the two anims. And you can have faded transparency on MNG too unlike gif.

  10. #10
    Guild Journeyer Tear's Avatar
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    I tried with Safari 4.0.3 for Windows.

    No MNG.

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