We don't have anything against layers. The layers paradigm has always been an interesting and powerful UI approach for document-oriented environments, such as CAD applications and drawing applications. In an object-oriented environment such as PixInsight, layers can also be useful, and even funny, because they allow for some kind of interaction that is more difficult to implement with separate images. I hope a layers tool will make PixInsight more appealing to those who are heavily accustomed to the layers paradigm, and hence a more competing product.
The only problem with layers is in the way they are being used with other applications. Unfortunately, layers are now associated with the application of manual painting tools and other processes selectively, arbitrarily and without any algorithmic or documentary criteria. We think these practices are incompatible with astrophotography. Eventually, once we have a working layers tool (soon) and drawing tools (we'll have them integrated with layers in a future version), these procedures will also be easy with PixInsight. This won't change the fact that we'll always be against painting the images, though.
The new layers tool (we are still deciding on the final name; maybe it will be LayeredComposition, or just Layers for the sake of simplicity) is actually very nice and useful. In its first version, it implements a complete set of arithmetic pixel operations (Add, Subtract, Multiply, Divide), move operations (Copy, Minimum, Maximum), composition operations (ColorBurn, LinearBurn, Screen, ColorDodge, Overlay, SoftLight, HardLight, VividLight, LinearLight, PinLight, Difference, Exclusion), and bitwise logical operations (OR, AND, XOR, NOR, NAND, XNOR). In addition, it allows you to merge luminance, lightness and chroma components between successive layers. It implements layer masks and allows for real-time mouse and keyboard interaction to select and move layers. I'd like to have it ready for release at the same time as version 1.8, but I'm not sure if we'll be able to achieve that.
