Change png to jpg?

Discussion in 'Feedback and Suggestions' started by Ron H, Oct 22, 2012.

  1. Ron H

    Thread Starter AAC Fanatic!

    Apr 14, 2005
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    In this post, I attached this file. It was a .png on my computer. It was changed to .jpg, apparently by the forum software. Was this done to minimize file size? I see that my original .png file was about 3 times the size of the posted .jpg.
    No problem, I just hadn't seen this before.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Yep, it does that sometimes, though usually it is a .gif. .gif is my prefered format.
     
  3. Georacer

    Moderator

    Nov 25, 2009
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    Cool feature!

    However, I think under conditions a .png can be smaller. I haven't found which ones though.
     
  4. takao21203

    Distinguished Member

    Apr 28, 2012
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    .PNG can be reduced to 8bit or even less.
    24bit .PNGs are quite large.

    Some web site scripts inflate 8bit PNG to 24bit- they sometimes become unreasonably large.
     
    Georacer likes this.
  5. Audioguru

    New Member

    Dec 20, 2007
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    I have also had my very clear PNG file changed to a fuzzy JPG file by the software in this forum.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I am using the .png image format for posting schematics.
    I am reducing the colors to 8 Bits deep, to reduce its size.
    The 24 Bits .png files can get converted to .jpg, to reduce space.

    Bertus
     
  7. Ron H

    Thread Starter AAC Fanatic!

    Apr 14, 2005
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    How do you do that?
     
  8. bertus

    Administrator

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    Last edited: Oct 22, 2012
    Georacer likes this.
  9. panic mode

    Senior Member

    Oct 10, 2011
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    i am running Windows and using IrfanView as image browser/manipulator that supports many file formats. It handles file conversions, and various functions like crop, rotate, effects etc. It is light and fast and - free.

    for test I used screenshot with particular display content and saved it as BMP (no compression) so I could use it as same input and generate different outputs:

    test 1: GIF , size 149kb
    this file format is pretty good for graph content like computer generated artwork (windows etc.).
    small file size, no artefacts but colour degradation was easy to see because GIF only supports up to 8-bit colours. this file format was infamously used to extort royalties, after it was used royalty-free for years. that was the main reason it was abandoned. it was great for computer generated content (lines, frames, windows etc.). for nature (people, photography) JPG was much better but neither GIF not JPEG could solve all problems. there is an improved JPEG (extension JP2) but it is not free. then PNG came along and saved the day.

    test 2: JPG, high quality (set as "100"), size 578kb
    bearable file size, some color degradation and no significant compression artefacts other t.

    test 3: JPG, med quality (set as "60"), size 166kb
    reasonable file size but more compression artefacts and more colour degradation.

    test 4: PNG, 24BPP (compression set to 0), size 3Mb
    nice image but way too large file for forum attachments

    test 5: PNG, 24BPP (compression set to recommended value 6), size 162kb
    nice image, no observable artefacts or color loss, small file size
    minute color loss can be seen only in direct comparison.

    test 6: PNG, 8BPP with compression value 6, size 120kb
    Menu: Image: Decrease Color Depth, 8BPP then save as PNG with compression value 6.
    even smaller file but looks like GIF, color degradation while noticeable it is still less than that of GIF.

    As shown, some experimenting can help determine optimum but I would say that leaving everything as is, and using recommended compression setting for PNG produces very good results.
     
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  10. #12

    Expert

    Nov 30, 2010
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    I've been using MS Paint for so long that I've gotten good at it. (That means minimum time wasted looking for features and the quality is pretty good, etc.) Anyway, I've been saving as PNG and the file sizes are pretty small, probably because I only use black and white. MS Paint doesn't have setting options. Lucky me, huh? It works for stupid people :)

    I see here that PNG's can be outrageously large, so, Mods: which "save as" does this site prefer? Whatever makes it fairly small?
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    Most nOObs post their first schematic as an extremely fuzzy Jpeg instead of as a very clear PNG.

    I used an old PAINT program to make schematics for many years but now I have a new PAINT program that is completely different. I must learn it all over again.
     
  12. Georacer

    Moderator

    Nov 25, 2009
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    I usually use .png to save computer generated images, such as MSPaint scribbles and schematics.
    I leave photos in their original .jpeg format, but I reduce their size to 800x600 when uploading them for a more easy to use resolution.

    I believe that the filesize might actually increase if one converts a real-life image from .jpeg to .png. I don't have proof, though.
     
  13. Ron H

    Thread Starter AAC Fanatic!

    Apr 14, 2005
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    Yeah, but the new Paint is WAY better than the old one, and the learning curve, for me, was not steep at all.
     
  14. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The main difference between life photos and a drawing is the number and randomness of colors.

    Bertus
     
  15. Georacer

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    Nov 25, 2009
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  16. bertus

    Administrator

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  17. Georacer

    Moderator

    Nov 25, 2009
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    That's more like you!
     
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