GIMP Version: 2.8.14
Operating System: Windows
OS Version: Home 64 bit
GIMP Experience: New User

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Without using Gmic I want to learn how to fade photos into a background. The GMIC plugin 'seamless' doesn''t always work for me so if I know how to just by using Gimp I won't need to use it. Feather often leaves a white halo.
Tutorials anyone?

You could use a photo mask over it, like this:

Original Photo:





With Photo Mask:



I used the photo mask from a set of spill frame layers by Katie Pertiet:

https://www.designerdigitals.com/digital-scrapbooking/supplies/product_info.php/products_id/25224

Thank you enxio27. What is a photo mask?
I think I worked out the reason for halos in feathering - you have to add an alpha channel before feathering.
Just did this one

@sallyanne

It is worth practicing with layer masks, a really powerful Gimp function.

A default white layer mask is 100% transparent Black is 100% opaque. Varying grey is varying transparency.

Now that Gimp 2.10 uses GEGL for gradients you get to see on the canvas the effect of painting in the layer mask. An easy transition might look like this using a linear gradient. Different effect with a circular gradient. Layers do not have to be the same size.



Or, the other way round, black layer mask, paint in white with a fuzzy brush to 'uncover' the subject. The advantage? The whole layer + layer mask can be moved to adjust position.



Easy, non-destructive, can be adjusted anytime.



Some edge masks (100 or so) + utility scripts + demo here:
https://www.gimp-forum.net/Thread-Easy-Edge-Masks

tried it using a radial gradient - using my method plus an eraser - didn't spend a lot of time on it as you can probably see.

I like the expression on its face.

Nearly there, practice makes perfect better.

You can still go round the edges (in the layer mask) with a fuzzy brush to touch-up any hard lines.

Blending with gradient does not work well with all images.
With the image you are playing with, I'd use a sharp brush to paint over the stone on the layer mask, so that the grass looks natural in front of it. The brushes Gimp includes, "bristles 01" and "bristles 02" would be good for grass and fur.
After that you can play with the Hue-Saturation & Brightness-Contrast on the animal/object layer to make it blend even better with the background.

Here's a quick demo. Dog from wikimedia over random garden image.



Painted most off with a round big brush on layer mask. This step could be done also with eraser on the layer itself.



Switch from mask to layer to use Hue-Sat now, so that you can see the effect of colors and lighting has when blending images.
Increased saturation little and reduced lightness. Then a bit of contrast with Brightness-Contrast.
The new Hue-Chroma in 2.10 is also good for this kind of tweaking.



Cleaning rest around the dog using "bristles 02" black brush on layer mask. Size 14-17 with this image.
Brush hardness reduced to 50.
You have the possibility to make corrections later with layer mask method, but here's why I normally make first perfect .png cutout of the object I wish to blend over the background.
Not that you always have to, but 9 times out of 10 there will be leftover pixels when you brush.



Fixed, now the dog can sit and oversee anywhere in the garden it (or he or she?) wants.

Sallyanne, check this script of Greachan's. I do not know if it works in 2.10.



viewtopic.php?f=8&t=3257

It doesn't work in 2.10, and the constantize plug-in won't fix it fully either.
I've attached fixed version, with one of the settings changed (Leave faded areas transparent) so that you will automatically end up with feathered transparent edge.

Just a reminder that with recent Gimp 2.10's you can apply a layer mask to a layer group, Which makes it easy to apply different fades.

A quick example using a couple of edge masks each with sort of fade (distressed border) applied.



..and remember unlike applying a script, a layer mask is non-destructive.
No pixels were harmed making this image

Hehe. Yeah that's a good tip. We should always seek solution from the built-in features of Gimp.
The fade-outlines.scm does create a layer mask though.

Thank you for fixing the script, Nidhogg. Very nice of you.

You're welcome pat625.