Image processing

You will find information on file formats, resolutions and footers for the graphics, the provision of which is mandatory for using the DFG Viewer, here. In this context, we can essentially differentiate between the logos to be displayed in the Viewer and the actual digital representations.

File formats

The GIF and JPEG formats are particularly suited for displaying in the browser. Even though both formats have their disadvantages (GIF graphics can consist of at maximum 256 colours, while JPEG images can only be compressed subject to losses), they have become very widely used on account of a lack of suitable alternatives and, consequently, they are supported by all common browsers. As a result, GIF is a good choice for the logos, while the digital representations should be saved in the JPEG format.

On account of its considerable file size the uncompressed BMP format is unsuitable and the same applies to the TIF format, which is widely used in digitisation and often contains a number of image metadata. Although the modern PNG format is superior to the GIF and JPEG formats referred to above, it is unfortunately not interpreted correctly by older browsers in case it contains transparencies.


The library and optional sponsor logo has to be available with a resolution of 108x50 pixels in any case. Of course, you are absolutely free in its design. It is displayed in the top left resp. right section in the standard layout of the DFG Viewer and it is linked to the web site whose address you have specified in the metadata file. Usually, this would be your library's homepage. Information and models are provided in the examples.

On principle, you can specify a different logo and/ or a different link for every digital representation – such as a logo and link to a sponsored project from which the digital representation originates. More detailed information on this is provided in the description of the metadata format.

The digital representations have to be provided with a standard resolution:
  1. In the standard view the digital representation is displayed with the highest resolution available.
  2. Optionally: If you also provide individual pages and/ or entire documents in the PDF format additionally, the DFG Viewer automatically displays a download button via which the user can download the current page and/ or the entire document.
  3. Optionally: The page preview displays several pages at once in an overview and permits graphic navigation through the document. This function requires smaller versions of the digital representations with at maximum 150 pixels in height and width.


The inclusion of a footer is recommended to identify your digital representations. This does not only enable the user to determine the origin of the digital representations at first glance but the user can also find further information if applicable. For example, the specification of a persistent URL or of the URN of the digital representation, which would permit quotation in a scientific context, might be conceivable.

Moreover, the recommendation that the footer to be included in every individual image should be kept in grey shades or black and white and equipped with the logo of the digitising library as well as the logo of the German Research Foundation applies with regard to digital representations from projects sponsored by DFG. Notes and models are included in the examples.