BlackRenderer is a Python-based renderer for OpenType COLR fonts, with multiple backends. It supports the new COLRv1 format as well as the old COLR format. It fully supports variable fonts, including variable COLRv1 data.
BlackRenderer comes with an hb-view-like command line tool, that can be used like this:
$ blackrenderer font.ttf ABC🤩 output.png --font-size=100
There is a high level function to render a text string:
from blackrenderer.render import renderText
renderText("myfont.ttf", "ABC", "output.png") # or "output.svg"
The full renderText()
signature is:
def renderText(
fontPath,
textString,
outputPath,
*,
fontSize=250,
margin=20,
features=None,
variations=None,
backendName=None,
)
For more control, the library exposes two main parts: the BlackRendererFont class, and a set of backend classes. Each backend provides a Canvas class. You pass a Canvas instance to a BlackRendererFont instance when drawing a glyph. Most backends also have a Surface class, which is a generalized convenience class to produce a canvas for a bitmap (or SVG document) for a specific box. Here is a minimal example:
from blackrenderer.font import BlackRendererFont
from blackrenderer.backends import getSurfaceClass
brFont = BlackRendererFont("my_colr_font.ttf")
glyphName = "A"
boundingBox = brFont.getGlyphBounds(glyphName)
surfaceClass = getSurfaceClass("skia")
surface = surfaceClass()
with surface.canvas(boundingBox)
brFont.drawGlyph(glyphName, canvas)
surface.saveImage("image.png")
Canvas objects support the following transformation methods:
canvas.translate(dx, dy)
canvas.scale(sx, sy)
canvas.transform((xx, yx, xy, yy, dx, dy))
Save/restore is done with a context manager:
with canvas.savedState():
canvas.scale(0.3)
...draw stuff...
If you have a Python 3 environment set up, then all you need to do is:
$ pip install blackrenderer
Have Python 3.7 or higher installed.
Open Terminal.
"cd" into the project repo directory.
Create a virtual environment:
$ python3 -m venv venv --prompt=black-renderer
Activate the venv:
$ source venv/bin/activate
(You need to activate the virtual environment for every new terminal session.)
Upgrade pip:
$ pip install --upgrade pip
Install the requirements:
$ pip install -r requirements.txt
$ pip install -r requirements-dev.txt
Install blackrenderer in editable mode:
$ pip install -e .
Run the tests:
$ pytest
To cut a release, make an annotated git tag, where the tag is in this format: v1.2.3, where 1, 2 and 3 represent major, minor and micro version numbers. You can add "aN" or "bN" or "rc" to mark alpha, beta or "release candidate" versions. Examples: v1.2.3, v1.2.3b2, v1.2.3a4, v1.2.3rc.
The message for the annotated tag should contain the release notes.
Then use "git push --follow-tags" to trigger the release bot. Example session:
$ git tag -a v1.2.3 -m "v1.2.3 -- fixed issue #12345"
$ git push --follow-tags
This process will create a GitHub release, as well as upload the package to PyPI.