[cairo] Limitation of recording surface

Adrian Johnson ajohnson at redneon.com
Wed Feb 4 04:41:24 PST 2015

On 04/02/15 20:05, Bernhard R. Fischer wrote:
> Hi!
> I'm developing Smrender which is a chart renderer for OSM data and I use 
> cairographics for it. Those charts are highly complex and contain a huge 
> amount of vector data.
> Internally, everything is rendered to a recording surface which is finally 
> "painted" to a PDF surface (or other formats).
> I found out that with some amount of input data the PDF is degraded to a 
> raster image instead of vector image.
> Is there any known limit in the recording surface or in the PDF surface which 
> causes this behavior? Is there any possibility to change this or do you have 
> any suggestions what I can do to avoid this?

No. As long you do not use operators unsupported by PDF it should not be
rasterized. If you are only using CAIRO_OPERATOR_OVER and seeing
rasterization in pdf it is likely a bug.

> Examples:
> The following two charts are rendered on the same system, same software, same 
> version...
> The only difference is that for the 2nd (raster) PDF more input data (contour 
> lines) is used. You can clearly see (if you zoom in) that the first one is a 
> vector image and the second is a raster image. The first also has embedded 
> fonts which the 2nd does not have.
> http://www.abenteuerland.at/download/eagle/murter_vector.pdf
> http://www.abenteuerland.at/download/eagle/murter_raster.pdf
> Best regards,
> Bernhard

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