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Thread: Compression Info (Formerly: Tips on Keeping Your Entry under 75kb in size.)

  1. #1

    Post Compression Info (Formerly: Tips on Keeping Your Entry under 75kb in size.)

    Please post any tips on keeping low file sizes here.

    One of the parameters in this month's competition is to keep entry file sizes under 75kb but with a resolution of at least 1280 x 1024 pixels in either jpg or png formats.

    As our community are used to producing maps in the low megabyte file size range, this parameter is likely to present one of the most formidable challenges in the competition if, like me, you do not know much about file compression and the pros and cons of jpg v png.

    If you are a file compression master, then please post your explanations and tips here for those of us who are technically less adept.

    Redrobes and gameprinter have already given some invaluable advice as follows:

    • Solid blocks of color and PNG would probably win. The very worst thing for all images is random noise followed by thin lines ! If you have a door in an old school map then its better being solid rect than an open box for example. Also, lines that are horizontal and vertical will be much better than ones at an angle. With JPG its a bit more complicated knowing what shapes would compress better as all the compression isl done in frequency space. JPG will have about 16K minimum size even if its all white but PNG would be a few hundred bytes. Also, ensure you save your PNG with specific number of colors 1, 16, or full. If you have < 16 colors then don't save full color as its hugely more expensive.
    • no anti-alias, minimal colors, etc, is completely unnecessary to still create a map that falls under 75 KB and at 1280 x 1024 pixel JPG. The difference is maximum compression JPG file and the best compression method.
    • The antialiasing is only going to make minimal difference. With PNG it would add a little but with JPG anti aliasiing would likely drop the size a little !

  2. #2


    The rules recommend a scale of 5 - 10 pixels per foot as a useful scale.

    This means that if you are using the minimum resolution of 1280 X 1024, you are looking at a map that is between 128 and 256 feet across by between 102 and 205 feet high.

    A picture below shows relative scales.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  3. #3
    Community Leader NeonKnight's Avatar
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    Aug 2007
    Surrey, Canada, EH!


    Thanx! That is the best bit of info I have seen so far!
    Daniel the Neon Knight: Campaign Cartographer User

    Never use a big word when a diminutive one will suffice!

    Any questions on CC3? Post them with CC3 in the Subject Line!
    MY 'FAMOUS' CC3 MAPS: Thunderspire; Pyramid of Shadows; King of the Trollhaunt Warrens; Demon Queen's Enclave

  4. #4

  5. #5


    a free image re sizer for Microsoft xp

    direct link:

    page it is found on is at:

    Click image for larger version. 

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  6. #6


    Once the May challenge is done, I think we should move this thread into the Software Discussion forum. There are already lots of good tips and utilities that it would be handy to have there. Or maybe it should just be appended to the end of the Image Export Formats thread.
    Bryan Ray, visual effects artist

  7. #7


    Some good advice from RobA:

    The trick here is that jpg compression is designed for photos (or photorealistic images).

    It is horrible for diagrams. You would probably get a better reproduction with a 2 bit gif on the diagram you posted.

    -Rob A.
    Last edited by RobA; 05-07-2008 at 10:28 AM.

  8. #8


    Good article on minimising jpeg file sizes here.

    Good article on minimising png file sizes here.

    I've also just discovered that .jpg and .jpeg are the same (someone please correct me if I'm wrong!)

  9. #9


    You are correct. The shorter .jpg extension was made necessary because MS-DOS and early editions of Windows had a three-character limit on extensions. .tif and .tiff are also interchangeable for the same reason.

    Since small file sizes in PNG depend on the number of colors used, those using that form of compression may want to review the color scheme generators linked here:

    Reducing your image to a few colors can greatly improve compressibility, but it makes choosing the right colors more important. Those of us who are stronger technicians than artists can use some help with that.
    Bryan Ray, visual effects artist

  10. #10
    Administrator Redrobes's Avatar
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    Dec 2007
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    Quote Originally Posted by ravells View Post
    Good article on minimising jpeg file sizes here.

    Good article on minimising png file sizes here.

    I've also just discovered that .jpg and .jpeg are the same (someone please correct me if I'm wrong!)
    Nice links except that as I read the first line it was wrong ! A JPEG is usually 24 bit but you can also do a greyscale JPG too. Thats a single channel version. That would sound like it would be 1/3 size but usually its nowhere near as small as that but it is smaller than a color one by maybe 20%.

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