Bug 506918

SUMMARY

The levels, color adjustment curves, and cross-channel color adjustment filters let you choose a "channel" to adjust using a button that displays a dropdown list for you to select the channel.

Normally, when you have a button like this, it means you have CHOSEN a specific channel (see the Halftone filter, for example). However, for these filters, this selector acts like a tab button. If you make changes to the Red channel and switch to the Green channel, you haven't changed your choice of which channel to affect, you have simply changed which channel you are currently viewing the curves of to edit. The curves for the Red channel stay in effect. They weren't reset. You simply can't see them anymore.

FIRST USABILITY ISSUE

You can't tell which channels HAVE been edited and which channels are in their default setting.

This could be solved by simply adding an asterisk (*) next to the channel name in the dropdown when it has been modified.

SECOND USABILITY ISSUE

On filter layers and filter masks, the filter always defaults to the first choice even when a different channel has been edited.

For example, if you make a Levels filter that operates on the Alpha channel and try to edit it, the dialog should display the RGBA channel that hasn't been modified instead of the Alpha channel, which is a confusing experience.

THIRD USABILITY ISSUE

You can't tell at first glance which channels have been modified and which have not. Even if an asterisk (*) were added, you need to open the dropdown to see this.

To remedy this would be a bit more complicated, as the dropdown would have to be replaced with tabs or with a list in a side pane (like the styles in the layer styles dialog). I think this would be the ideal, but I'm not sure if it would actually look good in practice since I've never seen a software do this.

A simpler alternative solution would be to display a text label that reads "2 channels active" or simply "(2)" next to the channel selector to indicate how many channels are currently active.

ADDITIONAL INFORMATION

On GIMP 3, although the dropdown is fancier with icons, there is no indication of which channels have been edited. Photopea doesn't have them either. Both software use the dropdown button instead of tabs, however, just like Krita does currently.