Compress different parts of a pix by different amounts?

Discussion in 'Digital Photography' started by mike, Oct 5, 2007.

  1. mike

    mike Guest

    I don't know the proper terms, but here's the idea.
    Take a big pix at high resolution (eg spectators at a football game).
    Use a combination of pixel scaling and compression to
    get a highly compressed picture, small file size, picture 1.
    Print picture 1.
    Print the original picture.
    Take scissors and cut out small parts of the high resolution
    (eg a face)
    pix and glue them on Picture 1 in the right places.

    Wanna do that digitally.

    I want small file size. I want the big picture for context.
    I want high resolution in a few small parts of the picture.
    I'd like to render the picture on a windows PC without extra stuff.
    Would be nice to be able to put the pix on a website and have
    a standard PC browser render it correctly. I want it freeware.

    Thanks, mike
    mike, Oct 5, 2007
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  2. mike

    Paul Bartram Guest

    Don't know if this is exactly what you mean, but XAT.COM Image Optimizer has
    a 'magic compression' setting that only selects areas of unchanging colour
    and density and hammers those while leaving the intricate areas alone. I use
    it for compressing files to below a certain size for uploading to a website,
    and it seems to work well. I think the older versions are now freeware, or
    the current ones are available for trial.

    Paul Bartram, Oct 5, 2007
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  3. mike

    JL Guest

    Paint Shop Pro Photo X2 (12) does it but not freeware.
    And it creates the html code for including in the webpage.

    Using PSP, you cut the image in rectangles and apply a different compression
    rate to each different rectangle.

    You may download the trial version (30 days) on The trial
    version is the complete version but limited in time.

    Jean-Luc ernst
    JL, Oct 5, 2007
  4. mike

    mike Guest

    Thanks for the tip.
    I tried it. In an uncontrolled experiment on one picture, I found it
    to be ineffective.
    Started with an 800KB jpg at 98% quality level.
    Loaded that into the xat program. With the quality slider at 50% and
    "magicness slider at 50% the
    output file size was about what I got with Irfanview.
    Maximum magicness reduced the file size a few percent.
    Minimum magicness increased the file size 20%.
    If you just move the magicness slider, you do see a difference in file
    size, mostly on the bigger end.
    But when compared to Irfanview, it's not very impressive.
    You get more benefit from reducing the quality level a point.

    For the pictures I tried, it's not very magic.

    As I described in the original question, the crowd picture
    is gonna be very busy. I don't expect anything automatic to
    I think I need to compress MANUALLY SELECTED areas differently.
    I remember tripping over such a program once, but have no idea the
    context or location. And my freeware constraint is likely to be
    a show-stopper.
    mike, Oct 5, 2007
  5. mike

    mike Guest

    Thanks, but 326MB download, $99 and HUGE system requirements put it
    out of the range of feasibility. I'll build a system to try it,
    tomorrow when the download finishes... just for fun, but it won't be
    practical for me.

    Anything lighter weight that will run in win2k available?
    mike, Oct 5, 2007
  6. mike

    Pat Guest

    I suppose if you wanted the maximum result, you need to create two
    layers. The bottom layer is the entire picture. Take that image and
    reduce it's size (in dpi) but keep it the same position in your
    software. Usually a screen is 72 dpi, so say, for the sake of
    argument you reduce it to 36 dpi. That's 1/4th the size. Then take
    the top (full resolution) image and cut out everything but the faces.
    Then merge the layers and export as a jpg. I believe that will let
    your compression software work better because you're gotten rid of
    lots of detail.

    Alternatively, you could set your colors in the "low res" area to, say
    8 color, and keep the faces at full color and reduce the data that way.
    Pat, Oct 5, 2007
  7. Many compression schemes, like the one used in JPEG and others, DO
    compress some parts of an image more than others.
    Don Stauffer in Minnesota, Oct 5, 2007
  8. mike

    Mike S. Guest

    JPG Wizard from Pegasus Imaging lets you manually select areas and group
    them according to the amount of compression (versus the rest of the
    image). V2 is payware but there is a "last freeware" copy of V1.x floating
    around somewhere.
    Mike S., Oct 5, 2007
  9. mike

    Paul Furman Guest

    Jpeg compression does that. You can help it along by masking out the
    detailed areas and blurring the unimportant areas, then the compression
    will be stronger in the blurred areas. Probably even non-lossy
    compression (png?) would work with that trick.
    Paul Furman, Oct 5, 2007
  10. mike

    Marvin Guest

    In an image editor like Photoshop or Paint Shop Pro, you can
    select parts of the photo and blur them. All parts of an
    image must have the same number of pixels per inch, but they
    don't have to be equally sharp. Another way to make one
    part of the image stand out is to leave it in color while
    making the rest grayscale.
    Marvin, Oct 5, 2007
  11. mike

    ray Guest

    Sounds impractical. In order to change compression methods on different
    areas would require additional information on the technique for each area
    - would probably lead to a bigger file than you started with.
    ray, Oct 5, 2007
  12. mike

    mike Guest

    Thanks, guys.
    Jpg wizzard does the job.
    Is it me or is the posting retention on this newsgroup about six hours?
    mike, Oct 5, 2007
  13. mike

    JL Guest

    I'm afraid PSPP X2 will not run on an old Win2K system.

    Jean-Luc Ernst
    JL, Oct 5, 2007
  14. PhotoLine 32, It has the option to compress individual layers, or
    portions by making them into new smaller layers, at whatever compression ratio
    that you want for each layer. Then combine those portions to your advantage
    using masks or mask brushes. Or use its adaptive-soften or adaptive-sharpen
    filters. Each automatically leaving the other portions alone. Then compress
    normally, the jpg algorithm normally applies more compression to the less
    detailed portions.

    There's lots of ways to do this using PhotoLine. But I find the web-export
    feature to provide all the compression and detail retention that I require.

    The huge added advantage is that for downsizing (before compression) it has
    Lanczos-8 resampling interpolation. No details are lost or softened, like what
    happens when using any version of PhotoShop or Paint Shop Pro with their
    bicubic-only methods.
    bradly-shanks, Oct 6, 2007
  15. mike

    Paul Bartram Guest

    It's you, I think. I have two newsfeeds (free.teranews and and one has 2500 headers, the other 8500*.

    You can subscribe to the Telstra one without a password - it's supposed to
    be read only, but I'm posting this through them.


    *That's several months worth.
    Paul Bartram, Oct 6, 2007
  16. mike

    JL Guest

    You should try the NEW algorithm when downsizing with Paint Shop Pro Photo
    X2. It produces now sharp images after downsizing (no soften nor lost of
    details). It is an improvement compared to the previous versions.

    Jean-Luc Ernst
    JL, Oct 6, 2007
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