When I export a page with a high-resolution embedded bitmap as a PDF, there is an option to alter the DPI of rasters, but it doesn't seem to work. I remember Adobe Acrobat had a feature like "Optimize PDF" or "Reduce Filesize" which allowed you to reduce the DPI of embedded rasters - can Inkscape do something like this?

Thanks

marko77 wrote:there is an option to alter the DPI of rasters

The dpi are used for the rasterization of filter effects if 'Rasterize filter effects [x]' is checked, not for bitmap images linked to or embedded in the SVG file in general.

You can use the rasterization of filter effects though to trick inkscape into changing the dpi of such bitmap images by applying an identity filter effect (a filter effect with parameters which result in no visible effect) to them: e.g. the 'Color Matrix' filter primitive with default matrix values, or the 'Blend' filter primitive with the mode 'Normal'. Then adjust the dpi value as needed when saving a copy as PDF/PS/EPS.

See also: Bug #246677 in Inkscape: “No raster resolution options for PDF save”

marko77 wrote:When I export a page with a high-resolution embedded bitmap as a PDF, there is an option to alter the DPI of rasters, but it doesn't seem to work. I remember Adobe Acrobat had a feature like "Optimize PDF" or "Reduce Filesize" which allowed you to reduce the DPI of embedded rasters - can Inkscape do something like this?

Thanks

I know what you mean - where acrobat will actually "scale down" the image throwing out pixels when saving as a new pdf.

For the best quality you are better off scaling the image you want to use in inkscape in a raster program before importing it into inkscape.

Alternately, you can use the Extensions->Raster->Resample to sample down the embedded images, but they must be done one at a time as you specify the new pixel size for the image.

EDIT: It might be nice to have a check box in that extension to resample to the image "size" the image currently is scaled to inside Inkscape, but for now you will have to just specify it manually.

-Rob A>

You can use the rasterization of filter effects though to trick inkscape into changing the dpi of such bitmap images by applying an identity filter effect (a filter effect with parameters which result in no visible effect) to them: e.g. the 'Color Matrix' filter primitive with default matrix values, or the 'Blend' filter primitive with the mode 'Normal'. Then adjust the dpi value as needed when saving a copy as PDF/PS/EPS.

YES!
I wish I had found this earlier! This is a great way to embed a raster image inside an EPS, preserving the vector parts of the rest of the image. I wanted to preserve the pixelation of the raster part, and keep the vector stuff with infinite zoomability of the other parts for a scientific publication that required EPS figures. I am so happy to have found this ... 5 hours later, but found eventually! Great trick