Skin Color Scheme Architecture

Overview

Creating a new skin from scratch is a lot of work and involves editing a lot of images - not very sensible when merely creating a different colored version of a skin. The color filtering architecture in Mixxx makes it easy to create a differently colored version of a skin.

Tips and Tools

For a "walkthrough" on creating schemes, see Skin Color Schemes Tips and Tool. It also contains a link to an online Javascript tool that will help determine correct HSVTweak values.

Color Scheme Demo

Mixxx comes pre-loaded with several skins, some of which support color schemes.

How to change a skin and the skins color scheme in Mixxx:

Go to Options -> Preferences -> Interface`
Select one of the skins like in the picture below
Select a scheme from the drop down menu and click Apply/OK

If you select a skin that does not support color schemes, the Scheme drop-down menu is grayed out.

Default Color Scheme (Classic) for Shade skin (Depicted here for Mixxx 2.3)

Alternative Color Scheme (Dark) for Shade skin (Depicted here for Mixxx 2.3)

Technical Stuff

There are two basic techniques of color changing implemented:

color filtering, for changing the colors of pixmaps
a color schema style sheet

Additionally, you can use variables to make widget templates use different source images, for example configuring pushbutton icons. Check skin.xml of the LateNight skin in Mixxx 2.3: schemes adjust waveform colors, font sizes and many other aspects of skin widgets.

The color filtering architecture is implemented as a chain of plugins which are queried by the user interface code as the skin is initialised. The filter chain is configured by a series of elements in the skin's skin.xml file.

So the core of the structure is laid out in src/skin/imgsource.h. Most filters will be implemented as an ImgColorProcessor. Some examples are in src/skin/imgcolor.cpp. To implement a new ImgColorProcessor you need to create a new class which implements the function doColorCorrection and performs some color mapping. The hooks for using the filters in a skin.xml file are in src/skin/colorschemeparser.cpp.

The capability is also there to implement non-color based filters by extending ImgProcessor directly, although it's important to note that the filter is applied to individual pixmaps as they're loaded, not to the skin as a whole. So for example a blur filter wouldn't blur the edges of a control outside the rectangle of the pixmap.

Scheme Format

To implement schemes in a skin there needs to be a color scheme section added to the skin.xml. See Creating Skins for reference.

General structure of the color scheme section in skin.xml.

<Schemes>     // General color scheme opening tag to tell Mixxx the skin supports color schemes
    <Scheme>  // Opening tag for Scheme#1 (default scheme)
        <Name>11pm (Dark Mixxx)</Name> // Scheme name
        <Filters>     // Opening tag for color filters
            <Invert/> // Invert filter, inverts the skins original images (i.e. white to black)
            <HueInv/> // Hue Invert Filter, sets hue to that of the inverted images
            <Add>     // Look at the "Filters" section for the specific filters and their arguments
                <Amount>50</Amount> // Filter value
            </Add>
            <ScaleWhite>
                <Amount>1.5</Amount>
            </ScaleWhite>
            <Add>
                <Amount>-50</Amount>
            </Add>
        </Filters>    // Closing tag for color filters
    </Scheme>
    
    <Scheme> // Another scheme
        <Name>5pm (Classic Mixxx)</Name>
        <Filters/>    // blank filter,the skins original images too be shown
    </Scheme>
    
    <Scheme>
        <Name>8pm (Summer Sunset Mixxx)</Name>
        <Filters>
            <HSVTweak>
                <SMin>100</SMin>
                <VFact>0.7</VFact>
                <HFact>0.3</HFact>
            </HSVTweak>
            <HSVTweak>
                <SMax>50</SMax>
                <HFact>0</HFact>
                <HConst>50</HConst>
                <SConst>120</SConst>
                <VConst>-10</VConst>
            </HSVTweak>
        </Filters>
    </Scheme>
    
    <Scheme>
        <Name>3am (Still Awake Mixxx)</Name>
        <Filters>
            <Invert/>
            <Add>
                <Amount>50</Amount>
            </Add>
            <ScaleWhite>
                <Amount>1.5</Amount>
            </ScaleWhite>
            <Add>
                <Amount>-50</Amount>
            </Add>
        </Filters>
    </Scheme>
</Schemes>      // general closing tag for color schemes

Filters

The filters have only been implemented as a quick test so far. At the moment we have (with their arguments):

Invert - Inverts image
HueInv - Sets hue to that of inverse. For example inverse followed by hueinv is equivalent to a hue invariant inverse.
Add - Adds a constant value to all color components (clipped to 0-255)
Amount - Value to add (int)
ScaleWhite - Scales low saturation (<50) colors by a factor
Amount - Factor to multiply by (float)
HSVTweak - Manipulate the Hue Saturation Value (HSV values), probably the most useful one
HMin - Minimum hue to modify
HMax - Maximum hue to modify
SMin, SMax, VMin, VMax - As above but for saturation and brightness
HFact, SFact, VFact - Factor to scale values by
HConst, SConst, VConst - Constant to add to values