Problems with plotting caused by rasterization of vector data

Problem:

Plot quality is poor:

• Oblique lines appear sawtooth-like (stair steps), their width varies somewhat as a result.
• Round lines appear jagged.
• Texts appear messy.

When outputting to PDF, the following special effects occur:

• When plotting to a PDF file with layers, not all vector layers are listed in the layer view. However, the content of the PDF file is complete and there is an "image" layer.
• When plotting to a PDF file, (freely available) fonts were not embedded. However, the content of the PDF file is complete and the texts with the non-embedded fonts are present. The texts may look a bit messy.
  
  

Cause:

• Rasterization of the vector data is taking place.

Rasterization means that vector data is converted into raster data. Rasterization is performed for each vector layer,

• that is below a raster layer in the representation hierarchy,
• which is located in the same group layer in which a raster layer is located,
• which has a layer transparency,
• which has bitmap picture symbols,
• which has area symbols with a transparency.

A vector layer that is rasterized acts like a raster layer. It causes rasterization in the group layer and rasterization of all vector layers below it in the representation hierarchy. Rasterization is therefore contagious.

Solution:

• There should be no vector layer below a raster layer in the presentation hierarchy.
  Note: WMS services usually return raster data as well.
• Group layers should contain either only raster data or only vector data, they should never be mixed.
• Do not use transparency for vector layers.
• Avoid the use of bitmap picture symbols. Instead, use vector-only EMF images or font-based character marker symbols (character font).
• When outputting to PDF, EPS, EMF and AI there is still an option to vectorize picture symbols with bitmap markers/fills. Then the bitmap picture symbols are transformed into vector data before plotting and are no longer raster data. Thus, these bitmap picture symbols no longer cause rasterization of the vector layer.
• Do not use area symbols with a transparency.

The quality of vectorization depends on the chosen resolution (dpi) (more is better). To set the resolution of raster data low and at the same time the resolution for calculations high, there is the ratio switch (resampleRatio). The resolution of the raster data can thus be significantly reduced compared to the general resolution.