Transparent colours open darker

[Kitty Saya]

When you open an image that contains semi-transparent colours, it displays them much darker.

How to reproduce:
1. Create a new image.
2. Fill the entire image with a colour, for example, blue.
3. Set the opacity to the frame it's in to for example, 127.
4. Save the image and close Pinta.
5. Re-open the image in Pinta.
6. Take a sample of the blue color.
7. Look at its values: they have changed, in my example from being #0000FF to #00007F.

Pinta Version: 1.6