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Additional file formats

How to use additional files | Guidelines for specific types of additional file | Additional file formats

Additional files can be submitted in any format. Instructions are available below for the most commonly submitted file types:

EPS (Encapsulated PostScript)

Most artwork-creation applications can save in, or export as, EPS format. Please refer to the software documentation for specific instructions. Non-standard fonts should be embedded.

EPS can be used for images produced by vector-drawing applications such as Adobe Illustrator or CorelDraw. However, EPS tends to be a bulky file format, compared with PDF which is a more modern and compact functional equivalent of EPS, so submission of figures in PDF format is encouraged.

We advise that you crop an EPS image using the same software as was used to create it (refer to the manufacturer's documentation).

If you have problems cropping your EPS image then, as a last resort, you may consider rasterizing it (converting from vector to bitmap format) using Photoshop, cropping the bitmap (again using Photoshop) and submitting the resulting bitmap image in TIFF or JPEG format. However, rasterization will typically increase file size and reduce quality, compared with a vector image.

PDF (Portable Document Format)

PDF is an excellent, modern image format, which can contain both vector and bitmap elements.

To ensure high quality, it is vital to choose the right settings when creating PDFs. Whether using Adobe Acrobat Distiller or other tools for PDF creation, authors should choose the appropriate options to create high resolution PDFs suitable for print use. This means ensuring that all artwork within the PDF is at a suitable resolution (300 dpi or more, at the intended final size of the figure) and that any non-standard fonts are embedded.

PDF files should be compatible with Acrobat 5.0 onwards (i.e. PDF version 1.4).

Authors should ensure that PDF files are not password protected as this prevents BioMed Central working with the file and can render such files incompatible with earlier versions of Adobe Acrobat.

PDF files can easily be cropped using the full version of Adobe Acrobat. Select Crop Pages from the Document menu. The Crop Pages dialog box will appear. Change the page margins by using the up and down arrow keys for each margin (left, right, top, bottom).

Alternatively, cropping can be done by selecting the crop tool from the toolbar. Here the cropping boundaries are set by selecting a handle at a corner of the cropping rectangle, and dragging it to the correct size.

If you have problems cropping your PDF image then, as a last resort, you may consider rasterizing it (converting from vector to bitmap format) using Photoshop, cropping the bitmap (again using Photoshop) and submitting the resulting bitmap image in TIFF or JPEG format. However, rasterization will typically increase file size and reduce quality, compared with a vector image.

DOC (Microsoft Word)

Word is a suitable choice for submitting figures and text containing both vector and bitmap elements.

Ideally, please do not submit in Office 2007 (DOCX) format, and consider converting to PDF, for improved accessibility.

PPT (Microsoft PowerPoint)

Powerpoint is another good option for submitting files containing both vector and bitmap elements, for authors who do not have access to a specialized drawing package.

Ideally, please do not submit in Office 2007 (PPTX) format, and consider converting to PDF, for improved accessibility.

TIFF (Tagged Image File Format)

TIFF is a bitmap format that is suitable for photographic/scanned images etc. It supports lossless compression (LZW compression) which works especially well for flat color images such as line art and screenshots.

We recommend that TIFFs are saved with LZW compression, as this allows higher resolution for a given file size. If an uncompressed TIFF is uploaded, BioMed Central's system compresses it automatically. For this reason, the size reported for a TIFF file following upload, may be smaller than the size of the uncompressed file uploaded.

TIFF and other bitmap images can be cropped using any photo or graphics editing package, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

JPEG (Joint Photographic Experts Group)

JPEG is a 'lossy' bitmap format - in order to maintain a small file size, some information in the image is discarded. In order to maintain as much image quality as possible, JPEG files should be saved at Maximum quality. See graphic below for a comparison of quality settings.

Courtesy of Bates et al., BMC Developmental Biology 2006, 6:33

Maximum-quality JPEG image

Courtesy of Bates et al., BMC Developmental Biology 2006, 6:33

Low-quality JPEG image

However, resaving low quality JPEG images with higher quality settings is not advisable, as it will only increase the file size without improving the quality of the image.

JPEG is a good choice for photographs, micrographs, autoradiographs etc. as the compression allows much higher resolution images to be submitted, for a given file size, with very little degradation of quality, provided the 'Maximum quality' setting is chosen.

JPEG is a poor choice for flat color images, line-art and screenshots as sharp edges create visible artefacts even at maximum quality settings. Such images are better submitted as TIFFs or PNGs.

Authors should minimize the number of times an altered version of an image is saved as a JPEG, as every time a modified JPEG image is saved, there is some degradation of quality. If possible, the work should be saved as a JPEG only at the end of any process of editing the figure.

JPEG and other bitmap images can be cropped using any photo or graphics editing package, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

PNG (Portable Networks Graphics)

PNG is a modern bitmap format that is suitable for photographic/scanned images etc. It supports lossless compression which works especially well for flat color images such as line art and screenshots. One advantage of PNG compared to TIFF is that PNG images can be displayed in modern web browsers.

PNG images can be cropped using most photo or graphics editing packages, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

BMP (Bitmap)

BMP is a Microsoft bitmap format that is suitable for photographic/scanned images etc, but is less standard and less compact than TIFF, PNG or JPEG and so is not a preferred format, although it is supported.

BMP images can be cropped using most photo or graphics editing packages, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

CDX (ChemDraw)

CDX is the file format for saving chemical reaction schemes prepared using ChemDraw. Suggested ChemDraw settings are:

  • Chain Angle 120°
  • Bond spacing 18%
  • Fixed length 0.406 cm (11.5 pt)
  • Bold width 0.056 cm (1.6 pt)
  • Line width 0.018 cm (0.5 pt)
  • Margin width 0.046 cm (1.3 pt)
  • Hash spacing 0.071 cm (2 pt)

TGF (ISIS/Draw)

TGF is the file format for saving chemical reaction schemes prepared using ISIS/Draw.

XLS (Microsoft Excel)

Microsoft Excel is suitable for the submission of large tables and charts.

Ideally, please do not submit in Office 2007 (XLSX) format, and consider converting to PDF, for improved accessibility.

TXT (Text)

Text Files are useful for the storage of information due to their simplicity.

ZIP

ZIP files are useful for compressing and archiving data. A ZIP file can contain one or more files that have been compressed to reduce file size.

RTF (Rich Text Format)

RTF enables cross-platform document interchange, as the majority of word processors are able to read and write this kind of document.

MOV (QuickTime Movie)

MOV is a common multimedia format, which is often used for saving movies and other video files. This format uses a proprietary compression algorithm developed by Apple Computer; compatible with both Macintosh and Windows platforms.

MPG

This is a common digital video format, which typically incorporates MPEG-1 or MPEG-2 audio and video compression.

AVI

AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback.

CSV (Comma Separated Value)

A CSV file is a specially formatted plain text file which stores spreadsheet or basic database-style information in a very simple format, with one record on each line, and each field within that record separated by a comma.

HTML (Hyper Text Markup Language)

HyperText Markup Language (HTML) is the predominant markup language for webpages, defining the layout and structure of text on a web page.

Files and URLs containing HTML will have an .html or .htm filename extension.

A collection of inter-linked HTML files should be submitted as a mini-website.

XML (Extensible Markup Language)

XML (Extensible Markup Language) is a set of rules for encoding documents electronically.

WAV (Waveform)

WAV is a Microsoft and IBM audio file format standard for storing audio bitstreams. It is the main format used on Windows systems for raw and typically uncompressed audio.

DAT (Data file)

DAT files are generic data files created by specific applications. They are not an ideal format to use, as they can typically only be accessed by the application that created the file. However, text within DAT files can sometimes be viewed using a text reader.

GIF (Graphics Interchange Format)

GIFs are suitable for sharp-edged line images with a limited number of colors. This takes advantage of the format's lossless compression, which favors flat areas of uniform color with well defined edges (in contrast to JPEG, which favors smooth gradients and softer images).

KML (Keyhole Markup Language)

Keyhole Markup Language (KML) is an XML-based language schema for expressing geographic data in two or three-dimensions.

KML can be used for geospatial biomedical data suited to 3D spatial visualisation. Google Earth will be used as a viewing application for KML data.

SBML (Systems Biology Markup Language)

SBML can be used to prepare models of biochemical reaction networks.

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