Digital Barcode Images and File Types

Summary:

When downloading digital barcode images:

  • Prefer vector formats (EPS)
  • Use high-quality desktop publishing software, such as Adobe Illustrator to produce final artwork
  • If producing bitmap/raster images (GIF, JPEG, PNG):
    • use highest possible resolution (600 dpi or higher)
    • avoid stretching and resizing of the image
    • use standard image magnification factors ( 80% - 200%) to obtain desired size

Producing Digital Barcode Images and Files

We are often asked: Which format is best for producing the highest quality barcodes? Below we are going to explain the important difference between several image formats that are commonly used. 
If you are producing artwork, labels or packaging that include barcode symbols and that are going to be printed you should know that there are many factors that are affecting the quality of printed barcode symbols.
This factors include:
  • the printing process itself
  • colours that are used for the bars and the barcode background
  • material used in the printing process
Your local GS1 office would provide you with best practice documents to assist you with producing barcode symbols that scan easily.

Barcode Image Types

Graphics can be stored nowadays in many several formats but there are two main categories: raster or bitmap formats and vector formats. 

Raster or Bitmap Images

Bitmap images are inferior format because they depend on the resolution with which they have been produced and on the device on which they have been printed. Any mismatch of these resolutions conversion from one bitmap format into another or stretching of the image will result in inexactness of the final image, which in turn might lead to the problems during the scan process. Therefore it is extremely important that the image is created with the same dot resolution of the printer.

In the example above, ( a PNG image produced at 300 dpi ) notice heavy rasterisation of central bars and human-redable characters. 

Vector or EPS Images

The best format for barcode images is a vector file format, instead of containing an actual raster style image (like a bitmap), a vector graphic contains a sequence of drawing instructions that describe how to render the image.  The best known type of vector images are EPS files ( Encapsulated Post Script files). This format defines exact dimensions of the bars in the barcode symbol. When the image is eventually converted to the printed elements during the printing the final dimensions of the barcode will be kept as accurate as printer will allow.

In the example above, ( an EPS image device-independent ) notice exact geometry of central bars and human-redable characters.

Relation between bar dimensions and device resolution

In standardised barcodes the most narrow elements are less than 0.5 mm wide. This thinnest elements of the barcode are called barcode modules. 
The different characters that barcode encodes will be expressed in combinations of these bars and spaces and are multiplications of of the module size. 
When using low resolution printing equipment ( example ink-printers or thermal transfer barcode printing machines that can be of 200 dpi resolution), then only two pixels are needed to produce bars that are 0.25 mm wide. This gives very little possibility to compensate for the ink-spread during the printing process since the only way to reduce the ink-spread is to 'shave' one pixel of two, which will make barcode inaccurate. 
When using high-resolution printing equipment a module will contain much more individual pixels there are more possibilities to compensate for ink-spread by removal of a whole column of pixels while maintaining the high resolution of the final barcode image.

Artwork

As far as final artwork is concerned please use DTP programs such as Adobe Illustrator, please do not convert the EPS file to bitmap when 'placing' or inserting the PostScript file.

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