Better Image Quality


Why do I get blurry file images? I did a clean Omeka 3.0.3 install with default appearance configurations.

Here’s what I get:

The image on the left is the square thumbnail preview and the image on the right is the image displayed after clicking the preview. Yo can see more clearly the blur I’m referring to if you click on the attachment and see the uploaded image at 100% size.

Here’s my original image:


One thing is that the thumbnails are always JPEGs, which are never going to be as perfectly crisp as a PNG like your original is. Square thumbnails, as the one you’re seeing there is, are going to be the most affected, especially if the size of your original is smaller than the configured square thumbnail size constraint (which might be the case here, as the original you show seems to be pretty small).

One thing you could try is setting the “version” option in the application/config/config.ini file. Setting this to your ImageMagick version can let us know you have a new enough version of ImageMagick that we can use a higher-quality method of creating the square thumbnails.

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Thank you. I will try setting ImageMagick version because I don’t think it has to do with image size or image format since my original image is 21 px bigger on both sides than the generated image thumbnail size and I also get this blur on photographs as jpg images.

Changed version option like this:

fileDerivatives.strategy = "Omeka_File_Derivative_Strategy_ExternalImageMagick"

fileDerivatives.strategyOptions.version = “6.9.10-68”

And here is the result:


It is better but it’s still not perfect.

It seems that default also reduces image size.

I’d expect a certain amount of blurriness unavoidably as a result of both going from png to jpg and from the slight resize. We probably can’t ever totally eliminate that. You can configure the system to use the non-square thumbnails instead on the frontend, which you might prefer.

Thank you. Do you think that it can have better results with the latest Image Magick?