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Vanilla 1.1.10 is a product of Lussumo. More Information: Documentation, Community Support.

General Support: Vertical image quality

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      CommentAuthortjk
    • CommentTimeFeb 22nd 2006 edited
     
    I have met the priblem with viewing images (large) with a height bigger than width.

    Not depending on the dimentions of an imported image i get a loss of quality with "vertical" pictures. Horizontal stay ok.

    Example: http://tjk.cc/events/index.php?level=picture&id=3160
    The original file has the same dimentions (http://tjk.cc/events/images/year_2005/godskitchen__zeppelin_pro___16-17.12.05_/img_6214.jpg) and the quality is fine.
    The maximum width is set to 500. This means my image is smaller and should be displayed as it is... so why does plogger decrease the quality? (it is set to 85 so there should be no loss like on example)
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      CommentAuthormike
    • CommentTimeFeb 22nd 2006
     
    I'm sorry, I looked at both your thumbnail and your original images and I can see no percievable difference in quality. Looks good to me!

    Maybe you changed the quality setting without clearing the thumbnail cache?
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      CommentAuthortjk
    • CommentTimeFeb 23rd 2006
     
    hmm... just compare the dark area below girls' neck

    i changed the quality straight after install...
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      CommentAuthorextremeg
    • CommentTimeFeb 23rd 2006
     
    If you upload a picture with a quality of 85% and you want no loss, don't you need to set the quality in plogger to 100%, otherwise you have an effective quality of 85% of 85%, which will give you a quality loss? Or is that me just being dumb???

    Look at this image which is the thumbnail:
    http://tjk.cc/events/thumbs/lrg-3160-img_6214.jpg
    And this, which is the orig image:
    http://tjk.cc/events/images/year_2005/godskitchen__zeppelin_pro___16-17.12.05_/img_6214.jpg
    and you can see it.
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      CommentAuthormike
    • CommentTimeFeb 23rd 2006
     
    Unfortunately, the compounding loss effect problem is unavoidable in this situation. Everytime you resample, resize, and resave a JPG image, you are losing a bit of quality as the compression is reapplied over and over again.

    Even at 100 for the "compression" setting you are getting a bit of loss from the compression algorithm.

    I guess I still don't see the problem here. I am looking at both images you posted (again) and there is very little loss of image quality. What is the issue here? The thumbnails are going to degrade in quality no matter what you do.
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      CommentAuthortjk
    • CommentTimeFeb 24th 2006
     
    oki. so does it work like extremeg said in hir reply above? is it 85% of the uploaded image?
    so if my uploading image is already 85% quality, than the image resized by plogger will be 72,25% (85 of 85)?

    I have no idea why, but i can't see this loss in a horizontal image (original images are bigger than maximum width), and the thing is that it appears only if the uploaded image is smaller than the maximum width parametr.
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      CommentAuthormike
    • CommentTimeFeb 24th 2006
     
    I don't think it is quite accurate to quantify the loss of quality as 72.25%. The JPG compression algorithm is quite complex, and compressing an already compressed image has very unpredictable behavior. It really depends on the bitmap in each individual situation.

    I really doubt this has anything to do with horizontal versus vertical image orientations. It is probably just a coincidence, and the actual determining factor for the degradation in quality is the complexity of the images themselves.
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      CommentAuthortjk
    • CommentTimeFeb 25th 2006
     
    i'm sorry mike, but you didn't answer my question. So is the operation of compressing already compressed image processed?

    so should i put a 100 quality in settings if i upload already compressed images or this will make the size of large images (kb i mean) grow?
    • CommentAuthorddejong
    • CommentTimeFeb 25th 2006
     
    If you want thumbs to keep their original image quality, they themselves need a quality of 100. It won't be exact, but it will be as close as possible.

    Mike is right that the quality of .85x.85 isn't exact, but you were right that the compression does compound.

    Cheers,
    Derek
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      CommentAuthortjk
    • CommentTimeFeb 26th 2006
     
    ok... thanks. i changed the setting. but how do i rebuild all thumbnails and large images so that they become 100 in quality? =)
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      CommentAuthormike
    • CommentTimeFeb 26th 2006
     
    Just delete all the images in your /thumbs/ directory, they will rebuild automatically.

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