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In the filter.plugins section of your dspace.cfg file, uncomment the ImageMagick media filter definition.

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This will activate the following settings which are already present in dspace.cfg:

    org.dspace.app.mediafilter.ImageMagickImageThumbnailFilter = ImageMagick Image Thumbnail, \
    org.dspace.app.mediafilter.ImageMagickPdfThumbnailFilter = ImageMagick PDF Thumbnail

These media filters contain the following configuration propertiesseveral properties which can be configured.

Thumbnail Dimensions

The following properties are used to define the dimensions of the generated thumbnails.:

# maximum width and height of generated thumbnails
thumbnail.maxwidth  = 80
thumbnail.maxheight = 80

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The ImageMagick media filters can differentiate thumbnails created by the DSpace default thumbnail generator and thumbnails that were manually uploaded by a user.  The media filter reads the bitstream description field to make this determination.  A A regular expression can be provided to define the set of thumbnails that should be overwritten by the ImageMagick thumbnail generator. Thumbnail descriptions matching this pattern will be overwritten even if the -f option is not passed to the filter media process.

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The ImageMagick media filter will use the bitstream description field to identify bitstreams that it has created using the following setting.  Bitstreams Bitstreams containing this label will be overwritten only if the -f filter is applied.

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DSpace uses the JPEG format for thumbnails. While JPEG doesn't support transparency, PDF, PNG and other formats do. As those formats are used as outgoing material in DSpace, DSpace has to care about transparency during the generation of the thumbnails. In combinations of specific versions of ImageMagick and Ghostscript it may occur , that completely transparent areas will become black. As a solution ImageMagick recommends to flatten images extracted from PDFs before they are stored as JPEG.

Since DSpace 5.2 the ImageMagick media filter flattens thumbnails extracted from PDFs. If you run into problems caused by flattening of the extracted images, you can switch the flattening off by setting the following property in dspace.cfg to false:

org.dspace.app.mediafilter.ImageMagickThumbnailFilter.flatten = false

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