GIMP Tutorial - Use Channel Mask & Threshold for Complex Selections by V...

GIMP Tutorial - Use Channel Mask & Threshold for Complex Selections by V...

Minnie the furry Lhasa Apso/Mix with simulated depth-of-field.

I use a lot of GIMP tutorials found all over the web for various projects. One of my go-to instructors is VscorpianC, be sure to check out her YouTube channel. I do a lot of graphic work as a volunteer at the local animal shelter, and often times I want to use a photo of a dog that has a crummy background, such as the one of Minnie, the 9-year old Lhasa Apso/Mix available for adoption, in the picture to the right.


To work with the photo I need to lasso the animal in GIMP and then either replace the background with a nice looking graphic or use a technique I learned from another tutorial found online called simulating depth-of-field (DOF), thanks to the GIMP Guru. This technique is easy enough to perform on a picture of a smooth-haired chihuahua or pitty, but on a Lhasa Apso... yeah all that fur makes lassoing the outline of the dog a real pain!

Using the color threshold and paintbrush to create a channel mask.

Luckily, I found VscorpianC's tutorial on using a channel mask threshold for complex selections. Using an image of a tiger with whiskers poking out against the background, VscorpianC clearly informs how to use GIMP's channels and color threshold to create a channel mask.

Layer mask.

After creating the channel mask, VscorpianC explains that you can add a layer mask and use the channel selection mask copy as a selection. From there you can replace the background if that is all you want to do. Or, create a simulated DOF, such as I did. Check out GIMP Guru's tutorial on simulated DOF.

Minnie in space. Photo by NASA, ESA. Acknowledgement: Josh Lake.