How to resize a picture down to 60% or down to 450 pixel (with keep aspect ratio)?

Peter

Based on your other post in the theme I would suggest to use gimp if you need to scale down your raster image. And also to use .png format instead jpg.

Ah, well I haven't seen the other message, at least not yet. So I don't know if it's raster or vector. But in case your topic title will be found by others searching, I'll give an overview.

While a raster image can be resized by Inkscape, it will still become pixelated, just as if it would if resized by a raster editor. But if it's a vector image, there are a couple of ways to scale an image or object in Inkscape.

1 - Selection tool -- be sure to click tiny padlock icon to close the lock, to keep perspective.
2 - Object menu > Transform > Scale and check box to keep proportion

Please note my forum signature for instructional material. Especially don't miss Help menu > Inkscape manual!

Hmm,

it's neither a raster nor a vector image. Its a simple *.jpg resp. *.png picture.

So resize is not possible here?
Peter

Well if it's an image file, it has to be either raster or vector. I don't know what "*.jpg resp. *.png" means. JPG is a raster format and so is PNG. So likely it's a raster image.

Resize is possible, but not without distortion (pixelation). But if it is a raster image, it would be better to use a raster editor, such as GIMP, to resize it.