Your backrground is a bit uneven (more light on the right). A scanner is better than a camera shot (scanners are cheap), or, next time, overexpose the shot.
This said:
This said:
- add a bit of contrast with the Brightness-contrast tool (watch for color changes on the line edges, stop before this)
- with the Levels tool blow out the bakcground (drag rightmost handle to the left)
Back to it. Found a way to even out the lighting, and af the same time whiten out the background:
- With the color picker, sample the darker background (bottom left corner) to set the foreground color
- With the same tool, sample the lighter backrgound (top right corner). Ctrl-click to set the background color
- Add a transparent layer, and set it to Divide mode
- Set the Gradient to FG to BG (RGB)
- With the Blend tool create a gradient ftrom the bottom left corner to the top right corner
- If happy with the result, "freeze" it with Layer>New from visible
- If needed you can add some saturation to that layer with Color>Saturation