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Guest MacMuffin

Possible thumbnail issues / incorrect orientation

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Guest MacMuffin

Hi all,


we have successfully completed our thumbnail migration project which will now instantly generate thumbnails on trades and the 15 minute delay will not apply any more. A further optimisation is that we now use a CDN (Content Delivery Network) which will optimise the delivery of thumbnails to the user which will result in faster page-load time.


Thumbnails are now also optimised to leverage browser optimisations. For example Chrome browsers support the WebP image format which allows smaller image files without sacrificing image quality. We are now also able to target our native applications with higher quality images (i.e. retina images for iOS retina devices or HDPI for Android devices) and images will automatically rescale based on the channel/device the image is presented.


During our tests we found that we have been able to reduce thumbnail image size by over 70% which will immediately benefit our users when browsing through products and searches.


We did however notice a small number of errors, where our automatic image rotation for thumbnail fails. Images taken via camera contain meta information about the rotation in EXIF data and our thumbnail process attempts to automatically adjust the orientation based on the EXIF information. In some rare cases, a user rotates an image using software that does not delete/adjust the image's original EXIF orientation information and then uploads the rotate image to our servers which would then result in a wrong thumbnail orientation.



We have made some further adjustments to hopefully detect and automatically fix wrong orientation information, but in the rare cases where you find a thumbnail to be displayed with a wrong orientation it is quite easy for you to fix the issue:


1) Download JHead - Exif Jpeg header manipulation tool

2) Run "Jhead -norot PictureFolder\**\*.jpg"


(The above command clears the Exif header rotation tag without altering the image. You may find that your images have rotation tags in them from your camera, but you already rotated them with some lossless tool without clearing the rotation tag. Now your friendly browser rotates the images on you again because the image rotation tag still indicates the image should be rotated.)

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