png resize bug?

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  • #1146494

    memming
    Member

    Automatic resize of png files generates distorted outputs. It renders without the resizing options at the end of URL, but gets distorted with it.
    For example, compare
    http://pillowlab.files.wordpress.com/2013/02/wang2012_blogpost.png?w=584&h=250
    with
    http://pillowlab.files.wordpress.com/2013/02/wang2012_blogpost.png

    Fromt the first image, what I see is
    http://pillowlab.files.wordpress.com/2013/02/screen-shot-2013-02-05-at-10-12-42-am.png?w=584&h=281

    It used to work, and sometimes it seems to come back, but most of the time it doesn’t work properly.

    The blog I need help with is pillowlab.wordpress.com.

    #1146591

    justpi
    Member

    That’s because the image is in indexed color. Needs to be RGB color.

    #1146592

    memming
    Member

    I see. Thank you.

    I wish wordpress.com will warn me about indexed color!

    #1146596

    memming
    Member

    Using imagemagick did the trick.

    convert a.png -color 10 b.png

    will make a RGB color table of size 10 from indexed color image a.png.

    #1146597

    justjennifer
    Moderator

    It is mentioned in the Image Troubleshooting Support doc http://en.support.wordpress.com/images/#troubleshooting

    Images should be saved in RGB mode, and you will see the best results if you use the sRGB color profile.

    #1146709

    memming
    Member

    I thought it was fixed, but after a week, the png is again rendered weirdly.
    Take a look at
    http://pillowlab.files.wordpress.com/2013/02/w.png?w=584&h=250

    It was resizing correctly for a few days and it broke again. What is going on?

    #1146710

    memming
    Member

    What the hell? After many forced refreshes, now it works again. This has to be a bug, right?

    #1146711

    justjennifer
    Moderator

    What browser and version are you using?

    #1146712

    w=584&h=250

    I’ve found it’s best not to use the size attributes, but to upload the correct size image to begin with.

    There are a number of free image editing tools to resize and recompress images. I think you’ll have better luck with .jpgs too over .pngs.

    #1146713

    memming
    Member

    I am testing on Chrome 25.0.1364.68 beta, and firefox 18.0.1. I’ve seen this happen on a couple of different computers.

    I like to have a smaller thumbnail display of a bigger figure, so that when you click on it you can see the full size figure. I guess I could upload them in two sizes and manually link them. But I don’t see why wordpress.com would provide the functionality, but incompletely.

    My image are originally vector graphics with sparse pixels. I wish I could use svg or pdf…jpg will be bad for these.

    #1146715

    justjennifer
    Moderator

    Beta versions of browsers are generally not supported and I just had a look in FF 18 and the PNG in this post looks fine http://pillowlab.wordpress.com/2013/02/05/lab-meeting-242013-asymptotically-optimal-tuning-curve-in-lp-sense-for-a-poisson-neuron/

    Have you tried just uploading your image and select to insert at Full Size and link it to the Media File? Otherwise optimize your image to the width of the content posting area for the theme you are using.

    #1146716

    memming
    Member

    Yes, it looks fine even in Chrome now. Thank you for warning about the beta version, but I do not believe that’s causing the problem.

    This problem comes and goes. Someday I’ll find the image garbled, and then after refreshing endlessly, it comes back to normal. I am suspecting that some of the backend media servers which are doing the resizing has problems. (Then if the load-balancer switches me to another backend, it goes away.)

    In full image size, I never had this problem.

    #1146717

    memming
    Member

    It’s happening again now, for both firefox 18 and chrome. I am testing from two computers with different IP addresses, and total of 4 browsers. All of them are showing a broken image now.

    #1146718

    memming
    Member

    I am using a proxy through a different country, and it shows correctly over there, but I still see garbled image through the computers with local address. I doubt this is because of a (transparent) cache.

    #1146719

    memming
    Member

    The image is recovered in one of my local machines, and also it works fine through a proxy in a different state within US, but it still shows a broken image on one of my computers!!

    #1146720

    memming
    Member

    And finally, now it’s working in all computers. Strange!

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