I was recently exploring a 2D Video Editing application, which has as one of its Effects, a Chroma-Key Effect, that will turn all the pixels in a given video-clip transparent, the colours of which are sufficiently close to a chosen, Key-Colour. And one of the simplest ways to configure this effect would have been, to open a colour-choosing dialog, and then to use a kind of eyedropper-tool, to pick the colour directly from the preview window of the Editing Application itself. But there was a glitch.
Because I have compositing enabled, and because the colour-choosing dialog fails to override this one behaviour of the compositor, as soon as the dialog opens, the rest of the screen is dimmed. And what that also means is, colours which I may choose from anywhere on the display won’t match the colours within the clip, that are to be made transparent.
And so the next place to look for a solution, might be, to install another application, such as ‘KColorChooser’, which has been programmed so that, even with compositing still running, the screen won’t be dimmed while it’s to be choosing a colour from that screen. But then I found that this application will save the chosen colour to its palette just fine, but that palette will not appear in any other program, nor within KColorChooser, the next time I open this helper-app. Therefore, colours must be transferred from one application to another, by saving their hex-codes to the clipboard.
There happens to be a way to simplify this task under Plasma 5.8, without having to install yet another application. With the full set of widgets to choose from, there is a bundled widget actually called “Color Picker”. The way to add it to our desktop is first, to Unlock the widgets, then, to pick Add Widget, then, to drag the widget in question from the widget selection bar, into the Quick-Launcher corner of the Panel. Even though globally, we may drag widgets to anywhere on an appropriately-unlocked desktop, this one is meant to be dragged into the Panel.
And so, with this additional quick-launcher, it’s possible to pick colours from the display, before the display gets dimmed, due to a window grabbing the foreground. Fortunately, this tool also copies the chosen colour’s code onto the clipboard as soon as we do that (unless we’ve changed a setting), and because the tool has not really quit, what it has copied to the clipboard will also stay there, for the main (in this case, video-editor) application to use. That main application only needs to support HTML/Hex colour-codes being pasted into its colour choosing field.
And, the quick-launcher’s second icon, from the two-icon set, opens a history of previously-picked colours, from which we may select one instead of doing so from the screen.