Question

There’s been a number of color swatch definitions over the years. To ensure we can store color managed color, as well as store other metadata we use, Krita has its own color palette format, KPL.

This document is a technical description of the format.

Basic Structure

KPL files are zip files containing the following files:

mimetype

A text file containing the mimetype, to differentiate it from a regular zip. application/x-krita-palette

colorset.xml

The main color definition file.

profiles.xml

This is a manifest of the icc profiles that are inside the zip file. We wanted to have no ambiguity in regards to which icc files were bundled.

A number of icc files.

These are the necessary icc profiles for interpreting the values in colorset.xml

profiles.xml

A manifest of the icc profiles that are inside the zip file. We wanted to have no ambiguity in regards to which icc files were bundled.

<Profiles>
   <Profile name="sRGB-elle-V2-g10.icc" filename="sRGB-elle-V2-g10.icc" colorModelId="RGBA" colorDepthId="F32"/>
</Profiles>

Krita doesn’t store every profile it uses. XYZ and LAB are colorspaces that only have one real space definition, and therefore it doesn’t make sense to embed these files.

colorset.xml

This is the main palette definition. It can handle comments, groups and more.

The top level element is a Colorset element, it’s children can either be ColorSetEntry elements, or Group elements. ColorSetEntry s that are direct children of Colorset are the ungrouped colors, and are, inside Krita, referred to as the “default” group.

<Colorset name="Scene Linear Swatches" comment="This is a palette for easy access to some swatches ready for scene-linear painting." columns="9" rows="1" readonly="false" version="1.0">

name

The human friendly name of the color palette.

comment

The description for the palette.

columns

The amount of columns in the palette in total. This is the same for all groups.

rows

The rows of the default group, see group for more info.

readonly

Whether the file can be edited.

version

The version of the file.

Group

Group elements can only have ColorSetEntry s as children. Group s are shown in the UI as a grid where the cells can be empty or contain a ColorSetEntry.

<Group name="Hot Colors" rows="5">
</Group>

name

The name of the group.

rows

The total amount of rows this group takes up, this, together with the column value in the toplevel Colorset element, determines the grid size.

ColorSetEntry

<ColorSetEntry name="Noon daylight at 0 EV" id="SI-D65-0EV" bitdepth="F32" spot="false">
  <XYZ space="XYZ identity built-in" x="0.17107713223" y="0.18000000715" z="0.17107713223"  />
  <Position row="0" column="0"/>
</ColorSetEntry>

name

The name of the color. Unlike the create swatches, we don’t support translated color names.

id

The id value. This is for complex colorsets where there is a human friendly name, and a name that uniquely identifies the color in the swatch database. In the above example, which encodes the D65 standard illuminant at 0 stops, SI-D65-0EV is a clear unambiguous id, but “Noon daylight at 0 EV” is a much more human friendly way to refer to it. Often, the ID is used for referencing spot colors inside files.

bitdepth

The bitdepth at which the color should be loaded. This is largely for our own convenience. Values are U8 (Unassigned 8bit integer), U16 (Unassigned 16bit integer), F16 (16 bit Floating Point), and F32 (32 bit Floating Point). Lab and CMYK don’t support F16, and for CMYK F32 is not recommended because it doesn’t deserialize the same way as the integer colorspaces.

spot

Whether or not the color is a spot color. This is currently not used elsewhere in Krita, but the intend is to use it for encoding spot colors as only the id.

ColorSetEntry s have two children:

The Position element is the position of the swatch inside the parent group grid. Krita doesn’t store empty swatches.

The other child element is a Create Swatch defintion. Krita supports Gray, sRGB, RGB, XYZ, CMYK, Lab and in theory YCrCb. Note that Krita supports unbounded colors as long as the bitdepth is F32.

Color swatch definition from the Create Wiki:

The following is the Color Swatch definition from the old create wiki . Krita largely uses this definition. Because the Create wiki is down, it’s contents are reproduced here. It is for reference only.

<colors xmlns:xlink="http://www.w3.org/1999/xlink">
    <color name="blue">
        <label lang="en">Blue</label>
        <label lang="es">Azul</label>
        <label lang="en_US_SoCal">glassy</label>
        <CMYK space="2ndFloorCMYK" c="0.8703" m="0.6172" y="0" k="0"/>
        <Lab space="mine" L="34.67" a="54.1289" b="-103.3359"/>
        <HSV space="prof01" h="240" s="1" v="1"/>
        <HLS space="prof02" h="240" l="0.5" s="1"/>
        <Luv space="prof03" L="34.6701" u="-15.0121" v="-124.7986"/>
        <XYZ space="prof04" x="0.1566" y="0.0833" z="0.7196"/>
        <Yxy space="prof05" Y="0.0833" x="0.1632" y="0.0869"/>
        <Gray space="prof06" g="0.2515"/>
        <sRGB r="0" g="0" b="1.0"/>
        <RGB space="lcd" r="0.1608" g="-0.1518" b="1.0753"/>
    </color>

    <color name="red">
        <label lang="en">Red</label>
        <CMYK space="2ndFloorCMYK" c="0.0011" m="0.7992" y="0.9405" k="0.0038"/>
        <sRGB r="1.0" g="0" b="0"/>
    </color>

    <colorspace name="2ndFloorCMYK" xlink:href="2nd_floor.icm"/>
    <colorspace name="mine" xlink:href="sample.icm"/>
    <colorspace name="lcd" xlink:href="generic_lcd.icm"/>
</colors>

Relax-NG for the swatches

namespace xlink = "http://www.w3.org/1999/xlink"
grammar {
start = element colors {
color+, colorSpace*
}
color = element color {
attribute name { text },
label *,
(RGB ? & sRGB ? & CMYK ? & Lab ? & HSV ? & HLS ? & Luv ? & XYZ ? & Yxy ? & Gray ? & YCbCr ?)
}
label = element label {
attribute lang { text } ?,
text
}
spaceAttribute = attribute space { text }
RGBAttributes =
attribute r { xsd:float },
attribute g { xsd:float },
attribute b { xsd:float }
RGB = element RGB {
spaceAttribute,
RGBAttributes
}
sRGB = element sRGB {
RGBAttributes
}
CMYK = element CMYK {
spaceAttribute,
attribute c { xsd:float },
attribute m { xsd:float },
attribute y { xsd:float },
attribute k { xsd:float }
}
Lab = element Lab {
spaceAttribute,
attribute L { xsd:float },
attribute a { xsd:float },
attribute b { xsd:float }
}
HSV = element HSV {
spaceAttribute,
attribute h { xsd:float },
attribute s { xsd:float },
attribute v { xsd:float }
}
HLS = element HLS {
spaceAttribute,
attribute h { xsd:float },
attribute l { xsd:float },
attribute s { xsd:float }
}
Luv = element Luv {
spaceAttribute,
attribute L { xsd:float },
attribute u { xsd:float },
attribute v { xsd:float }
}
XYZ = element XYZ {
spaceAttribute,
attribute x { xsd:float },
attribute y { xsd:float },
attribute z { xsd:float }
}
Yxy = element Yxy {
spaceAttribute,
attribute Y { xsd:float },
attribute x { xsd:float },
attribute y { xsd:float }
}
YCbCr = element YCbCr {
spaceAttribute,
attribute Y { xsd:float },
attribute Cb { xsd:float },
attribute Cr { xsd:float }
}
Gray = element Gray {
spaceAttribute,
attribute g { xsd:float }
}
colorSpace = element colorspace {
attribute name { text },
attribute xlink:href { xsd:anyURI }
}
}

Using for validating

To use the above RelaxNG compact schema to validate a swatch you can use:

trang -I rnc -O rng colors.rnc colors.rng
xmllint --relaxng colors.rng colors.xml

Color Grouping Proposal

Krita doesn’t use this.

<group>
    <label lang='en'>One group</label>
    <color name='red'>
        <label lang='en'>Red</label>
        <sRGB r="1.0" g="0" b="0"/>
    </color>
    <group>
        <label lang='en'>Nested group</label>
        ...
    </group>
    </group>
<group>