add dither option for image processing (esphome#1317)

* [Image] add dither option for image processing

* fix import order

* revert import location
and hardcode two dither method

* fix format

esphome/components/image/__init__.py

@@ -4,14 +4,14 @@
 from esphome.components import display, font
 import esphome.config_validation as cv
 import esphome.codegen as cg
-from esphome.const import CONF_FILE, CONF_ID, CONF_TYPE, CONF_RESIZE
+from esphome.const import CONF_FILE, CONF_ID, CONF_TYPE, CONF_RESIZE, CONF_DITHER
 from esphome.core import CORE, HexInt
+
 _LOGGER = logging.getLogger(__name__)
 
 DEPENDENCIES = ['display']
 MULTI_CONF = True
 
-
 ImageType = display.display_ns.enum('ImageType')
 IMAGE_TYPE = {
     'BINARY': ImageType.IMAGE_TYPE_BINARY,
@@ -28,6 +28,7 @@
     cv.Required(CONF_FILE): cv.file_,
     cv.Optional(CONF_RESIZE): cv.dimensions,
     cv.Optional(CONF_TYPE, default='BINARY'): cv.enum(IMAGE_TYPE, upper=True),
+    cv.Optional(CONF_DITHER, default='NONE'): cv.one_of("NONE", "FLOYDSTEINBERG", upper=True),
     cv.GenerateID(CONF_RAW_DATA_ID): cv.declare_id(cg.uint8),
 })
 
@@ -53,8 +54,9 @@ def to_code(config):
             _LOGGER.warning("The image you requested is very big. Please consider using"
                             " the resize parameter.")
 
+    dither = Image.NONE if config[CONF_DITHER] == 'NONE' else Image.FLOYDSTEINBERG
     if config[CONF_TYPE] == 'GRAYSCALE':
-        image = image.convert('L', dither=Image.NONE)
+        image = image.convert('L', dither=dither)
         pixels = list(image.getdata())
         data = [0 for _ in range(height * width)]
         pos = 0
@@ -76,7 +78,7 @@ def to_code(config):
             pos += 1
 
     elif config[CONF_TYPE] == 'BINARY':
-        image = image.convert('1', dither=Image.NONE)
+        image = image.convert('1', dither=dither)
         width8 = ((width + 7) // 8) * 8
         data = [0 for _ in range(height * width8 // 8)]
         for y in range(height):

esphome/const.py

@@ -159,6 +159,7 @@
 CONF_DISCOVERY_PREFIX = 'discovery_prefix'
 CONF_DISCOVERY_RETAIN = 'discovery_retain'
 CONF_DISTANCE = 'distance'
+CONF_DITHER = 'dither'
 CONF_DIV_RATIO = 'div_ratio'
 CONF_DNS1 = 'dns1'
 CONF_DNS2 = 'dns2'