So basically I use a png image in two different versions. First by just opening it in Inkscape and storing it as svg, for the second by clicking "convert to pattern" and then storing as svg. The first looks like this in the file:
<image
width="1280"
height="720"
preserveAspectRatio="none"
xlink:href="data:image/png;base64,iVBOR..."
id="image10"
x="0"
y="0" />
and the second like this:
<defs
id="defs6">
<pattern
patternUnits="userSpaceOnUse"
width="1280"
height="720"
id="pattern4157">
<image
y="0"
x="0"
id="image10"
xlink:href="data:image/png;base64,iVBOR..."
preserveAspectRatio="none"
height="720"
width="1280" />
</pattern>
</defs>
<sodipodi .../>
<rect
style="stroke:none;fill:url(#pattern4157)"
width="1280"
height="720"
x="0"
y="0"
id="rect4160" />
Now, if I export both svg files as png using inkscape, the first one is identical with the source png, the second one becomes a tiny bit blurry, the color also seems ever so slightly darker and also the filesize shrinks from 1.7MB to 1.3MB. Why does this happen? How can I avoid this?