Problem: Someone has created pictures that are 1726 x 1040. We have started using them in a gallery on a website.

It is pictures of fish, the originals where all different size. I have after a long time finally been able to cut out a fish of a picture, it is now just a fish and a white background. I am able to resize, keeping constants. But how do I make the image containing this fish be 1726 x 1040?

I am about three hours into this program so please excuse my idiotic question, it is just I am in a kind of hurry.

Regards.

I'm not sure whether I completely understand your question.
Do you mean white background or transparent background?

1. Set the page size (Shift+Ctrl+D) to 1726x1040 px and scale your fish to fit on it.
2. In the same dialog click on background color and set A:(alpha) either 0=transparent (default) or 255=white.
3. Export the page.

Sometimes setting the canvas background opaque does not result in an opaque background for the image.

In case it doesn't work, I would suggest this:

1 - draw a rectangle (1726 x 1040)
2 - if the fish needs to be larger, then scale it to the size you need
3 - select both the rectangle and the fish
4 - Object menu > Align and Distribute
5 - click Align on Vertical axis ()
6 - click Align on Horizontal axis () (using both those buttons makes the fish centered in the rectangle)
7 - If you want an opaque background, fill the rectangle with an opaque color. Or if you want it transparent, remove the fill completely.
8 - assuming you need a raster image (rather than SVG) select the rectangle, and File menu > Export PNG image (make sure DPI is set for 96)
9 - or if it needs to be an SVG image, go to Document Properties > Page tab > Custom Size > Resize Page to Contents, make sure all the margins are set for zero, then click Resize page.... button

Thank you both.
You actually also lead me to solve the next problem that came.

Regards
André