I make a photo calendar every year, and I like doing it freehand using layers. Is it possible to edit individual photos while they are in the layers on the calendar page? With Gimp or any other program? I often need to brighten or color-correct a photo so that it blends in with the other photos and doesn’t stand out on the page. It’s a real pain to have to leave the calendar page window, open the photo in a new window, tweak it, add it to the page, realize I need to tweak it more, edit again, add again… Can I adjust the brightness and color of individual photos right there in their own layers on the calendar page?
Yes, as long as they are in their own layers they are straightforward to edit.
However… if the image is 8-bit per channel, every color change you make induces a bit o color loss. So, after too many tweaks, you can start to see problems (such as banding). Converting to high precision (Image > Precision, and use 32-bit FP linear) will reduce this.
Thank you! I have been using PhotoScape, and I haven’t found any way to edit photos in layers with that program. I will install Gimp and give it a go! Thanks very much for your response. 
In Krita, you can adjust brightness with curve adjustment layer, and you can color-correct with Levels set to RGB and use the automated color-correcting tool built inside the Level filters in the same way. Krita supports adjustment layers/masks, so you can definitely preserve the original image, and yes you can copy directly into a layer too.
Pinta is supposedly simpler than the Gimp, and supports layers. https://www.pinta-project.com/
Pinta is a free, open source program for drawing and image editing.
Its goal is to provide users with a simple yet powerful way to draw and manipulate images on Linux, Mac, Windows, and *BSD.
1 Like
This one one of the real strengths of programs like GIMP (and Photoshop). You can adjust each layer separately. The trick is to make sure the layer itself is activated (selected) before doing color or brightness adjustments. If you need more advice just ask and I can provide some details. Also the user guide for GIMP is worth bookmarking and using for issues. I am an experienced user , but still refer to it it for information and guidance. GNU Image Manipulation Program