I realize that the issue I am describing won’t seem like unusual behavior for the mirroring tool, but please bear with me. I searched in settings and the manual for a way to resolve this issue but could not find what I was looking for, which is why I decided to post in this category.
Something I noticed happening while I was doing a study was that when I mirror the canvas, the reference images I put on with the Reference Images tool flip as well. When it happened, it didn’t seem like an unusual thing at first. But looking over the image and the references, it seems like erroneous behavior.
Firstly, one of the main uses of mirroring the canvas (in my opinion at least) is to check for symmetry and check your composition. For various reasons, including for studying, not getting “stuck” with a particular orientation of image-and-reference, and not having to shift your eyes from one end of the compo to the other, it seems like reference images should not mirror when the image is mirrored.
And second: To me as a user, “Mirror Image Horizontally” suggests that the option would only flip the parts of the image that would appear in an exported product. Reference Images don’t appear in any export, which causes me to treat reference images as part of the UI rather than as part of the composition. Therefore, when the reference images get flipped, it seems like strange behavior.
What are your thoughts on this?
(Additional note: It’s possible to flip each reference image on their own by dragging their anchor points all the way towards and past the centre of the reference image. AFAIK, you would need to do it for each image though, if you were to flip your image but wanted to keep references unmirrored.)
I don’t have a strong opinion on this, for my purposes I always liked the reference images being mirrored with the canvas. But I wanted to add that you can shift-click or just click and drag to select multiple ref images using the Reference Image Tool and use Transform > Mirror Horizontally from the right-click menu. Complementary, if you often tend to use Image > Mirror Image Horizontally (from the main menu) to mirror all layers without the ref images, best assign a custom shortcut to it through Settings > Configure Krita > Keyboard Shortcuts, or add it as a quick button to the toolbars from Settings > Configure Toolbars. https://docs.krita.org/en/reference_manual/main_menu/settings_menu.html#configure-toolbars
Snudl pointed out that you can flip the reference images all together. I managed to find out that using the same method outside of selecting reference images, you can flip your art without flipping reference images. In the top toolbar, go Layer -> Transform All Layers -> Mirror All Layers Horizontally. This means that the user has a choice between flipping your art with the reference images (using Mirror from the image menu) or without reference images (using the Mirror from the Layer menu)!
I’ve noticed an issue using either method with Assistants. Assistants do not flip with your image. This poses a problem if you’re using the parallel ruler to draw speed lines and flip your piece occasionally to check for composition, as the next set of speed lines you draw would be coincidental to the existing lines.
There is also an issue – though fixable using previously mentioned methods – with rotating your art. If you use the Layers menu to rotate your art, the reference images will not rotate but this option does not transform your canvas dimensions. On the other hand, using the rotate option from the Image menu does change your canvas dimensions, but also rotates your reference images. This can be fixed by using Snudl’s suggestion of selecting your reference images with the Reference Image tool, right-click, Transform -> Rotate – or just using the handles on the reference image just like you would on any vector.
The difference is that if you’re using the mirrored view, no extra calculations are done, so it’s instant. Mirror All Layers Horizontally can take a lot of time if you have a lot of big layers. Mirrored View just mirrors the view (so you’re seeing it flipped; check saving: after using mirrored view, the saved image will be still unmirrored; after using Transform → Mirror on layers, it will be saved mirrored, cause then the calculations are actually done)