The technique makes use of layers and layer masks in The GIMP, so it is important to have a basic understanding of what these are beforehand. The next section introduces these concepts and provides a ...

Then, move your mouse focus back to the image window and paste (Ctrl-V). In the Layers dialog, click the Anchor button to anchor the pasted image into the layer mask. After this step, your Layers ...

For more fine-tuned blending, you can apply a white layer mask to the top layer using the "Layer" drop-down menu. With a white layer mask, when you paint over the top layer, the bottom layer emerges.

Now highlight the Masked Layer that you just inverted, right-click, and select Add Layer Mask. In the dialog box that pops up, check the Selection radio button, then press Add.