info on converting NCL/NCARG images to other formats

From: Mary Haley (haley AT ucar.edu)
Date: Fri Oct 14 2005 - 00:55:10 MDT

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    Hi everybody,

    We've had a few inquiries lately on converting images created by NCL
    and NCAR Graphics to other formats like JPEG, PNG, and MPEG (for
    movies). I thought I'd post some information that I think might be
    useful, and I'd like to open up the board for anybody else to offer
    their own wisdom on this topic.

    Many of you have been using the ncgm2gif or ncgm2mpeg scripts to do
    conversions from NCGM to GIF or MPEG. Lately, however, I've been
    finding that these scripts don't always work well because our raster
    tools that these scripts depend on (like ctrans and rassplit) haven't
    been updated in awhile, and don't always work as expected.

    We unfortunately don't have the staff to focus on updating our raster
    library to the same level that other specialized raster tools are
    capable of. As such, I'd like offer some other solutions for raster
    conversions. Also, I've noticed that starting with NCGMs to create
    images for presentations doesn't always produce the best looking
    fonts.

    My recommendation is to start with a PostScript (PS) file, and then
    use "convert" from the ImageMagick suite of tools to convert the PS
    file to another format like GIF, PNG, or even MPEG.

    You can get the ImageMagick suite from:

        http://www.imagemagick.org/

    Click on the "download" link on the left side and you will be
    presented with lots of options for download locations.

    Mac users can download it using "fink install imagemagick". You must
    have fink installed first - http://fink.sourceforge.net/.

    Once you have the tools built and installed, you can convert your PS
    files to other formats using:

        convert -trim file.ps file.png

    I like to use the "-trim" option to remove unwanted white space around
    my image. This cuts it pretty close, so if you put it in a PowerPoint
    presentation, it is better to use a pure white background so the
    cropped image doesn't look funny.

    Documentation on "convert" can be found at:

         http://www.imagemagick.org/script/convert.php

    If you want to convert your PS file to an MPEG file for generating a
    movie, you can still use "convert". You may also need to download the
    program "mpeg2encode". The source code for this can be downloaded
    from:

        http://www.mpeg.org/MSSG/

    >From here you want to download the source code for "mpeg2vidcodec".
    The "mpeg2encode" code is pretty straightforward to build (in the
    directory mpeg2/src/mpeg2enc).

    Once you have mpeg2encode installed, you can convert your
    PS file to MPEG with:

       convert file.ps file.mpg

    There are lots of options available with convert, that, according to
    their web page, allow you to "resize an image, blur, crop, despeckle,
    dither, draw on, flip, join, re-sample, and much more."

    I will put this information on our websites, and meanwhile, I welcome
    input from others who have different ways of converting their NCL/NCAR
    Graphics images.

    Cheers,

    --Mary

    -------------------------------------------------
    Mary Haley haley@ucar.edu
    NCAR/SCD/VETS 303-497-1254 (voice)
    1850 Table Mesa Dr 303-497-1239 (fax)
    Boulder, CO 80305
    -------------------------------------------------

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