kpp

The kpp module offers an interface for interacting with and creating .kpp files that, once saved, can be loaded into Krita as a valid brush preset.

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Brief overview of the .kpp file format

".kpp files are PNGs which contain an annotation with the XML data for the brush engine" (quote from the Krita documentation.) For my purposes, I wanted to be able to create a .kpp file programmatically using any random image without needing to open Krita.

This is where kpp comes in. kpp allows for an existing .kpp file to be read and modified outside of Krita. Once saved, the resulting .kpp file can be loaded into Krita as a valid brush preset.

Like the Krita documentation mentions, a .kpp file is a PNG which has been annotated with XML data. There are a ton of brush settings within this data. To keep this to the point, we will focus on the settings that are important for loading a custom image into Krita as a brush preset.

The XML data stored within a .kpp file has one root element called Preset. The Preset element has a resources child and various param children. When an image is added to a .kpp file, it is stored as a child of the resources attribute. The value of a resource is the image as a byte array which has been decoded as latin_1.

A md5 checksum is generated using the contents of the given image and is referenced in the brush_definition parameter.

Here is a botched example of what that looks like:

<Preset name="a) cool brush name" embedded_resources="1" paintopid="paintbrush">
    <resouces>
        <resource name="cool_image" md5sum="generated from file contents" filename="cool_image.png" type="brushes">
            byte array decoded as latin_1
        </resource>
    </resouces>
    <param name="cool param" type="string">cool</param>
    ...
    <param name="brush_definition" type="string">&lt;Brush ... md5sum="must match md5sum in corresponding resource attribute" filename="cool_image.png" ...&gt;</param>
    ...
</Preset>

Requirements

• Python: 3.8 or later
• PyQt5: 5.15.2 or later

Recommended usage

It is recommended to start from a existing .kpp file. You can then tweak the parameters to your liking.

Note The brush angle in a brush preset is represented as radians instead of degrees. The brush scale is a percentage which is derived from the minimum and maximum brush sizes at the time the preset was saved.

from kpp import Kpp

kpp_file = r"path\to\kpp_file.kpp"

_kpp = Kpp.from_kpp(kpp_file)

# set kpp parameters
_kpp["name"] = "b) " + "cool_brush"
_kpp["paintopid"] = "paintbrush"
_kpp.filename = _kpp["name"]

# initialize resource as a local resource
# this makes the resource read only!
_kpp.resource.file = r"path\to\png_file.png"

# set brush parameters
_kpp.parameters["EraserMode"] = False
_kpp.parameters["brush_definition"].md5sum = _kpp.resource["md5sum"]
_kpp.parameters["brush_definition"].filename = _kpp.resource["filename"]
_kpp.parameters["brush_definition"].type = "png_brush"
_kpp.parameters["brush_definition"].angle = math.radians(30)
_kpp.parameters["brush_definition"].scale = 0.5

# add the preview image to the brush definition
preview_image = QtGui.QImage(_kpp.resource.file)
_kpp.preview = preview_image.scaled(
    200,
    200,
    QtCore.Qt.AspectRatioMode.KeepAspectRatio
)

# save the .kpp file to the given directory
saved_kpp_file = _kpp.save(directory)