epdlib 0.4.6.0

EpdLib is a library for creating dynamically scaled screen layouts for frame-buffered devices such as e-paper/e-ink displays.

epdlib v0.4

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.

Changes

v0.4

• Add support for IT8951 panels with 8bit gray scale and partial refresh
  • Assigning EPD object to screen has changed from directy assignment to using a the string that corresponds to the name. See the ChangeLog for details

Dependencies

Python Modules:

• Pillow
  • System dependencies for Pillow:
    • libopenjp2-7
    • libtiff5
• RPi.GPIO
• spidev
  • ensure SPI is enabled on the pi
• waveshare-epd (Non IT8951 based panels)
  • 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
• IT8951 (IT8951 based panels)
  • 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

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

Parent class for other types of blocks

Args [default value]:

• area(list/tuple): x and y integer values for dimensions of block area
• hcenter(bool): True: horizontally center contents [False]
• vcenter(bool): True: vertically center contents [False]
• rand(bool): True: randomly place contents in area [False]
• inverse(bool): True: invert pixel values [False]
• abs_coordinates(list/tuple): x, y integer coordinates of this block area within a larger image [(0, 0)]
• padding(int): number of pixels to pad around edge of contents [0]
• fill(int): 0-255 8 bit value for fill color for text/images [0 black]
• bkground(int): 0-255 8 bit value for background color [255 white]
• mode(str): '1': 1 bit color, 'L': 8 bit grayscale ['1']

Properties:

• image: None - overridden in child classes'''

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 acceptable
• area (2-tuple of int): area of block in pixles - required
• text (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 specified chardist
  • Default: None
• 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)
• 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

Methods

• update(update=None) - Update the text string with a new string and sets image 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 a str 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, force_onebit=False)

Scaling Example

epdlib Layout objects can be scaled to any (reasonable) resolution while maintaining internally consistent ratios.

500x500 Layout

300x200 Layout

Properties

• resolution (2-tuple of int): resolution of the entire screen in pixles
• layout (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
• force_onebit (bool): force all blocks within a layout to mode='1'

Methods

• concat(): join all blocks into a single image
  • sets image property
• 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}

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 (epd object)
  • waveshare epd object used for interfacing with the display
• update (obj:Screen.Update): monotonicly aware object that tracks time since last update
• rotation (int): [-90, 0, 90, 180, 270] rotation of screen
• mode(str): '1' for 1 bit screens, 'L' for screens capable of 8 bit grayscale
• vcom(float): vcom voltage for HD IT8951 based screens (not needed & ignored for non-HD screens)

Methods

• clearScreen(): Set a blank image screen
• clearEPD(): send the clear signal to the EPD to wipe all contents and set to "white"
• writeEPD(image, sleep=True, partial=False): write image to the EPD.
  • resets update timer
  • sleep: put the display to low power mode (default: True)
  • partial: update only chaged portions of the screen (faster, but only works with black and white pixles) (default: False)
• intiEPD() - initializes the EPD for writing
• blank_image(): produces a blank PIL.Image in of mode type of resolution dimensions
• list_compatible_modules(): print a list of all waveshare_epd panels that are compatible with paperpi

Example

import Screen
import waveshare_epd
myScreen = Screen()
myScreen.epd = "epd5in83"
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 creation
• now (float): time in CLOCK_MONOTONIC time
• last_updated (float): time in seconds since last updated
• update (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 keep
• prefix (str): prefix to add to filenames
• time (str): time in format: %y-%m-%d_%H%M.%S - 2020-02-29_1456.39
• img_array (list): list of files stored in path

Methods

• delete(img): delete img file
• save(img): save img to path
  • 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 Recipes

Quick Demo

The demo creates a very basic layout and displays some text in four orientations. This is an easy way to test your panel and confirm that it is working properly.

python3 -m epdlib.Screen

Creating an Image from a Layout

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.

import epdlib

# create the layout object - adjust the resolution to match the display area
layout_obj = epdlib.Layout(resolution=(640, 400))

l = { # basic two row layout
    'tux_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)
            'mode': 'L',                 # treat this image as an 8bit gray-scale image
        },
    'pangram_a': { 
                'image': None,           # set to None if this is a text block
                'max_lines': 3,          # maximum lines of text to use when wrapping text
                'padding': 10,           # padding around all edges (in pixles)
                'width': 3/4,            # 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': False,         # horizontal-center the text and the resulting image
                'vcenter': True,         # vertically-center the text within the block
                'relative': ['tux_img', 'pangram_a'], # 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-Regular.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
    },
    'pangram_b': { 
                'image': None,
                'max_lines': 2,
                'padding': 0,
                'width': 1,
                'height': 1/4,
                'abs_coordinates': (0, None),
                'hcenter': True,
                'vcenter': True,
                'relative': ['pangram_b', 'tux_img'],
                'font': './fonts/Open_Sans/OpenSans-Regular.ttf',
                'font_size': None,
                'inverse': True
    },
    'pangram_c': { 
                'image': None,
                'max_lines': 3,
                'padding': 0,
                'width': 1,
                'height': 1/4,
                'abs_coordinates': (0, None),
                'hcenter': True,
                'vcenter': False,
                'relative': ['pangram_c', 'pangram_b'],
                'font': './fonts/Open_Sans/OpenSans-BoldItalic.ttf',
                'font_size': None,
                'inverse': False,
    },    
    'text': {
                'image': None,
                'max_lines': 3,
                'padding': 10,
                'width': 1,
                'height': 1/4,
                'abs_coordinates': (0, None),
                'hcenter': False,
                'vcenter': True,
                'relative': ['text', 'pangram_c'],
                'font': './fonts/Open_Sans/OpenSans-Regular.ttf',
                'font_size': None,
                'inverse': True
    }

}

# apply the layout instructions to the layout object
layout_obj.layout = l

# create a dictionary with the values that will be pushed to each block
update = {
    'tux_img': './images/tux.png',      
    'pangram_a': 'The quick brown fox jumps over the lazy dog.',  
    'pangram_b': 'Pack my box with five jugs of liquor.',          
    'pangram_c': 'Jackdaws love my big sphinx of quartz.',                    
    'text': 'A pangram or holoalphabetic sentence is a sentence using every letter of a given alphabet at least once. '}

# update the layout with the data in the dictionary and send each item to the proper block
layout_obj.update_contents(update)

# join all the sub images into one complete image
myImg = layout_obj.concat()
# write the image out to a file
myImg.save('sample.jpg')

Write an image to a Screen

The following code will create an interface for writing images to the EPD Requirements

• Waveshare EPD module or IT8951 library (see Notes below)

from epdlib import Screen
from PIL import Image
## non IT8951 screens
my_epd = "epd2in7" 
my_vcom = None
## IT8951 screens
# my_epd = "HD"
# my_vcom = -1.8

# create screen object
my_screen = Screen(epd=my_epd, vcom=my_vcom)

my_resolution = my_screen.resolution

# open image, convert to 1 bit and scale
my_img = Image.open('path/to/image.jpg')
my_img = my_img.convert("1")
my_img.thumbail(my_resolution)

# write image to screen
my_screen.writeEPD(my_img)

# clear screen
my_screen.clearEPD()

Notes

The Waveshare-epd library is provided only as a git repo. Try the following to install it:

pip install -e "git+https://github.com/waveshare/e-Paper.git#egg=waveshare_epd&subdirectory=RaspberryPi_JetsonNano/python"

The IT8951 library is provided only as a git repo. Try the following ot install it:

pip install -e "git+https://github.com/GregDMeyer/IT8951#egg=IT8951"

getting ready for pypi: https://medium.com/@joel.barmettler/how-to-upload-your-python-package-to-pypi-65edc5fe9c56