blending backgrounds

[df23]

I have an image and i need to replicate part of the image and put this below the original image to create a longer image. I have done this by creating layers for the original and the partial copy. The background colour (in this case the sky) at the bottom of the original and the top of the copy are not quite the same. I need to be able to blur the sky colours together. I cant use the gradient because there are other parts in the image (ie not the sky) at the border between the layers which would be impacted.

Any suggestions on how this can be done?

thanks
Dave
Gimp 2.10

[rich2005]

Could do with some details of the images. Do you still have them in Gimp as separate layers?

You might do it with a layer mask:

Two layers with a (white) layer mask added. https://i.imgur.com/Ntgbf3s.jpg

Apply a black to white gradient to the layer mask. Using Gimp 2.10 so adjustment is easier with an on canvas mid-point adjustment: https://i.imgur.com/EUNsVT8.jpg

But then you have to go in and paint in the foreground (buildings in this case, could be a person) to restore the opacity: https://i.imgur.com/9Oy72OG.jpg

[df23]

(05-05-2019, 11:14 AM)rich2005 Wrote: Could do with some details of the images. Do you still have them in Gimp as separate layers?

You might do it with a layer mask:

Two layers with a (white) layer mask added. https://i.imgur.com/Ntgbf3s.jpg

Apply a black to white gradient to the layer mask. Using Gimp 2.10 so adjustment is easier with an on canvas mid-point adjustment:  https://i.imgur.com/EUNsVT8.jpg

But then you have to go in and paint in the foreground (buildings in this case, could be a person) to restore the opacity:  https://i.imgur.com/9Oy72OG.jpg

Thanks for your response. I have done the first two steps and i can see this has blended the sky between the two layers quite nicely.
I am not sure how to do the last bit. Presumably i have to draw around the items that should not be changed somehow, like the buildings in your example?

[rich2005]

Depends how steady your hand is. With a mask, black =transparency white=opacity greys=between the two.

Sorry about the image, the only one handy with a sky. After applying the gradient, paint inside the foreground.

This maybe a bit easier to see: https://i.imgur.com/gNK5vpO.jpg standard brush / white FG

For painting straight lines click-beginning / shift / click-end of line, or you could zip around the outline with free select, fill the selection with white.

If you wanted to make a selection of the foreground with the free select tool before applying the gradient then invert the selection -> apply gradient.