EpdLib is a library for creating dynamically scaled screen layouts for frame-buffered devices such as e-paper/e-ink displays.
Project description
epdlib
EpdLib is a library for creating dynamically scaled screen layouts for frame-buffered devices such as e-paper/e-ink displays. Complex layouts are defined as image or text blocks. Using epdlib blocks makes it trivial to develop for different disiplay resolutions as layouts are aware of thier resolution and scale the blocks dynamically to match the available area.
Dependencies
Python Modules:
- Pillow
- System dependencies for Pillow:
- libopenjp2-7
- libtiff5
- System dependencies for Pillow:
- RPi.GPIO
- spidev
- ensure SPI is enabled on the pi
- waveshare-epd
- this is for interacting with waveshare epaper displays and is not strictly needed to use the Block and Layout objects.
- see notes below for installation instructions
Modules:
- Block - image and text blocks that can be assembed into a final layout
- Layout - generate dynamic layouts from Blocks
- Screen - simple interface for waking and writing to WaveShare EPD devices
- epdlib
Table of contents generated with markdown-toc
Block Module
Block
objects are containers for text and images. Block
objects are aware of their dimensions and can be made aware of their position within a larger layout. Block
objects can also handle wrapping text and resizing images to fit within their borders.
Class Block(area, hcenter=False, vcenter=False, rand=False, inverse=False, abs_coordinates=(0, 0), padding=0)
Properties
area
(2-tuple of int): area of block in pixles - requiredhcenter
(bool): True - horizontally center image within block, center justify text- Default: False
vcenter
(bool): True - vertically center text within block- Default: False
rand
(bool): True - randomly place text within area of block (mutually exclusive of hcenter and vcenter)- Default: False
inverse
(bool): True - invert colors (black becomes white, white becomes black)- Default: False
abs_coordinates
(tuple): X, Y coordinates of upper left corner of image block within a larger layout- Default: (0, 0)
padding
(int): padding to add around text/image and edge of block- Default: 0
Methods
update(update)
Place holder method for child classes.
Block.TextBlock
Child class of Block
that contains formatted text. TextBlock
objects can do basic formatting of strings. Text is always rendered as a 1 bit image (black on white or white on black). Text can be horizontally justified and centered and vertically centered within the area of the block.
All properties of the parent class are inherited.
Class Block.TextBlock(font, area, text='NONE', font_size=0, max_lines=1, maxchar=None, chardist=None)
TextBlock
objects will attempt to calculate the appropriate number of characters to render on each line given an area, font face and character distribution. Each font face renders characters at a different width and each TTF character uses a different X width (excluding fixed-width fonts). Each language favors certain characters over others.
Properties
font
(str): path to TTF font face - relative paths are acceptablearea
(2-tuple of int): area of block in pixles - requiredtext
(str): string to format- Default: 'NONE'
font_size
(int): font size in points- Default: 0
max_lines
(int): maximum number of lines to use when wrapping text- Default: 1
maxchar
(int): maximum number of characters to fit on a line- if set to
None
, the text block will calculate this value based on the font face and specifiedchardist
- Default: None
- if set to
chardist
(dict): statistical character distribution for a supported language to use for a specified font- dictionary of letter and float representing fractional distribution (see
print_chardist
)
- dictionary of letter and float representing fractional distribution (see
image
(PIL.Image): resultant image generated of formatted text
Functions
print_chardist(chardist=None)
- print supported character distrubtions- chardist (str)
chardist='USA_CHARDIST'
print the character distribution for USA English
- chardist (str)
Methods
update(update=None)
- Update the text string with a new string and setsimage
property- update (str)
Block.ImageBlock
Child class of Block
that contains formated images. ImageBlock
objects do basic formatting of color, centering and scaling. All ImageBlock
images are 8 bit grayscale Pillow.Image(mode='L')
. Images that are too large for the area are rescaled using the Pillow.Image.thumbnail()
strageies to limit distortion. Images that are smaller than the set area will not be resized.
All properties of the parent class are inherited.
Class Block.ImageBlock(area, image=None)
Properties
image
(:obj:PIL.Image or :obj:str) -Pillow
image or path provided as astr
to an image file; relative paths are acceptable
Layout Module
Layout
objects support scaling images and dynamically scaling TTF font-size for different screen sizes.
Font sizes are set based on each individual font and scaled to fit within text blocks using the maximum number of lines specified in the layout. Text is line-broken using the python textwrap logic.
Class Layout(resolution, layout=None)
Scaling Example
epdlib Layout
objects can be scaled to any resolution while maintaining internally consistent ratios.
500x500 Layout
300x200 Layout
Properties
resolution
(2-tuple of int): resolution of the entire screen in pixleslayout
(dict): dictionary containing layout paramaters for each block- see example below in Quick-Start Recipe
image
(Pil.Image): concatination of all blocks into single image
Methods
- see example below in Quick-Start Recipe
concat()
: join all blocks into a single image- sets '
Functions
update_contents(updates=None)
- update the contents of each block- updates (dict)
- dictionary in the format
{'text_section': 'text to use', 'image_section': '/path/to/img', 'pil_img_section': PIL.Image}
- dictionary in the format
- updates (dict)
Screen Module
Screen
objects provide a method for waking and writing to a WaveShare E-Paper Display (EPD). Screen
objects are aware of their resolution and when they were last updated (stored in monotonic time).
Class Screen(resolution=None, epd=None)
Properties
resolution
(2 tuple of int): resolution in pixels- this is overriden by the epd object resolution when it is set
epd
(WaveShare EPD module)- the waveshare library that will be used for the actual writing of data to the screen
update
(obj:Screen.Update): monotonicly aware object that tracks time since last update
Methods
clearScreen()
- Set a blank image screenclearEPD()
- send the clear signal to the EPD to wipe all contents and set to "white"writeEPD(image, sleep=True)
- and writeimage
to the EPD.- resets update timer
- Defaults to putting the display to low power mode
intiEPD()
- initializes the EPD for writing
Example
import Screen
import waveshare_epd
myScreen = Screen()
myScreen.epd = waveshare_epd.5in83
myScreen.initEPD()
myScreen.writeEPD('./my_image.png')
Screen.Update
Create a monotonically aware object that records the passage of time.
Class Screen.Update()
Properties
age
(float): age in seconds since creationnow
(float): time in CLOCK_MONOTONIC timelast_updated
(float): time in seconds since last updatedupdate
(bool): True - trigger resets last_updated time
Methods
update(update=True)
- reset last_updated timer to zero
Example
import Screen
u = Update()
u.now
>>> 357147.118559987
u.age
>>> 37.449310125026386
u.last_updated
>>> 62.2587232599617
u.update = True
u.last_updated
>>> 0.00021347898291423917
Screen.ScreenShot
Capture a rolling set of screenshots. When the total number of screenshots exceeds n
the oldest is deleted. Images are stored as .png.
This is useful for debugging over time.
Class Screen.ScreenShot(path='./', n=2, prefix=None)
Properties
total
(int): total number of screenshots to keepprefix
(str): prefix to add to filenamestime
(str): time in format: %y-%m-%d_%H%M.%S - 2020-02-29_1456.39img_array
(list): list of files stored inpath
Methods
delete(img)
: deleteimg
filesave(img)
: saveimg
topath
- img: PIL.Image
import Screen
scrnShot = Screen.ScreenShot(path='/temp/', n=20)
spam = PIL.Image.new(mode='L', size=(100, 100), color=0)
scrnShot.save(spam)
Quick-Start Recipe
The following recipe will produce the screen layout shown above for a 640x400 pixel display. This image can be passed directly to a WaveShare e-Paper display for writing.
Creating a Layout Image
import epdlib
# create the layout object
myLayout = epdlib.Layout(resolution=(640, 400))
# define a layout
l = { # basic two row layout
'weather_img': {
'image': True, # image block
'padding': 10, # pixels to padd around edge
'width': 1/4, # 1/4 of the entire width
'height': 1/4, # 1/4 of the entire height
'abs_coordinates': (0, 0), # this block is the key block that all other blocks will be defined in terms of
'hcenter': True, # horizontally center image
'vcenter': True, # vertically center image
'relative': False, # this block is not relative to any other. It has an ABSOLUTE position (0, 0)
},
'temperature': {
'image': None, # set to None if this is a text block
'max_lines': 1, # maximum lines of text to use when wrapping text
'padding': 10, # padding around all edges (in pixles)
'width': 1/4, # proportion of the entire width
'height': 1/4, # proprtion of the entire height
'abs_coordinates': (None, 0), # absolute coordinates within the final image (use None for those
# coordinates that are relative to other blocks and will be calculated
'hcenter': True, # horizontal-center the text and the resulting image
'vcenter': True, # vertically-center the text within the block
'relative': ['weather_img', 'temperature'], # blocks to which THIS block's coordinates are relative to
# -- in this case X: `weather_img` and Y: `temperature`
# the width of the block `weather` will be used to
# to calculate the X value of this block and the Y value
# specified within the `temperature` block will be used
'font': './fonts/Open_Sans/OpenSans-ExtraBold.ttf', # TTF Font face to use; relative paths are OK
'font_size': None # set this to None to automatically scale the font to the size of the block
},
'wind': {
'image': None,
'max_lines': 3,
'padding': 0,
'width': 1/4,
'height': 1/4,
'abs_coordinates': (None, 0),
'hcenter': True,
'vcenter': True,
'relative': ['temperature', 'wind'],
'font': './fonts/Open_Sans/OpenSans-ExtraBold.ttf',
'font_size': None
},
'rain': {
'image': None,
'max_lines': 3,
'padding': 0,
'width': 1/4,
'height': 1/4,
'abs_coordinates': (None, 0),
'hcenter': True,
'vcenter': True,
'relative': ['wind', 'rain'],
'font': './fonts/Open_Sans/OpenSans-ExtraBold.ttf',
'font_size': None
},
'forecast': {
'image': None,
'max_lines': 7,
'padding': 10,
'width': 1,
'height': 3/4,
'abs_coordinates': (0, None),
'hcenter': False,
'vcenter': True,
'relative': ['forecast', 'temperature'],
'font': './fonts/Open_Sans/OpenSans-Regular.ttf',
'font_size': None,
'scale_y': .85
}
}
# apply the layout instructions to the layout object
myLayout.layout = l
# create a dictionary with the values that will be pushed to each block
update = {
'weather_img': './docs/Avatar_cloud.png', # weather_img block will recieve a .png
'temperature': '15C', # temperature block will receive `15C`
'wind': 'Wind East 3m/s', # wind block will recieve this text
'rain': 'Rain: 0%', # rain block
'forecast': 'Partly cloudy throughout the day with an east wind at 3m/s. High of 20, low of 12 overnight. Tomorrow: temperatures falling to 15 with an increased chance of rain'
}
# update the layout with the data in the dictionary
myLayout.update_contents = update
# join all the sub images into one complete image
myImg = myLayout.concat()
# write the image out to a file
myImg.save('./my_forecast.png')
Notes
The Waveshare-epd library is not provided in an easily usable format. As of 1 Oct 2020, it cannot be directly installed with pip
or pipenv
. The package maintainers have used a literal '&' character in the subdirectory for the library making it extra difficult to use. Try the following to install it:
pipenv install -e "git+https://github.com/waveshare/e-Paper.git#egg=waveshare_epd&subdirectory=RaspberryPi\&JetsonNano/python"
This will likely result in a heap of errors. The library is not installed, but it does fetch the source.
ERROR: Error [Errno 2] No such file or directory: '/home/pi/.local/share/virtualenvs/epdlib-AIMLabQa/src/waveshare-epd/RaspberryPi': '/home/pi/.local/share/virtualenvs/epdlib-AIMLabQa/src/waveshare-epd/RaspberryPi' while executing command python setup.py egg_info
ERROR: Could not install packages due to an EnvironmentError: [Errno 2] No such file or directory: '/home/pi/.local/share/virtualenvs/epdlib-AIMLabQa/src/waveshare-epd/RaspberryPi': '/home/pi/.local/share/virtualenvs/epdlib-AIMLabQa/src/waveshare-epd/RaspberryPi
Finally install the library with:
MYVENV=$(pipenv --venv) pipenv install -e $MYVENV/src/waveshare-epd/RaspberryPi\&JetsonNano/python
getting ready for pypi: https://medium.com/@joel.barmettler/how-to-upload-your-python-package-to-pypi-65edc5fe9c56
!jupyter-nbconvert --to markdown --stdout > README.md
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