def convert_color(rgb, a, truncate=True):
from pebble_image_routines import pebble_nearest_color_to_pebble_palette, pebble_truncate_color_to_pebble_palette, \
rgba32_triplet_to_argb8
r, g, b = (rgb >> 16) & 0xFF, (rgb >> 8) & 0xFF, rgb & 0xFF
if truncate:
(r, g, b, a) = pebble_truncate_color_to_pebble_palette(r, g, b, a)
else:
(r, g, b, a) = pebble_nearest_color_to_pebble_palette(r, g, b, a)
return rgba32_triplet_to_argb8(r, g, b, a)
def convert_png_to_pebble_png(input_filename, output_filename,
color_reduction_method=DEFAULT_COLOR_REDUCTION):
with open(output_filename, 'wb') as output_file:
input_png = png.Reader(filename=input_filename)
#open as RGBA 32-bit (allows for simpler parsing cases)
width, height, pixels, metadata = input_png.asRGBA8()
palette = [] # rgba32 image palette
is_grey = True # does the image only contain greyscale pixels (and only full or opaque)
has_alpha = False # does the image contain alpha
transparent_grey = None # transparent color matching greyscale value
# iterators are one shot, so make a copy of just the iterator and not the data
# to be able to parse the data twice (we do not modify the pixel data itself)
# once to generate the palette
# once to output the final pixel data as greyscale or palette indexes
pixels, pixels2 = itertools.tee(pixels)
#convert RGBA 32-bit image colors to pebble color table
for (r, g, b, a) in grouper(itertools.chain.from_iterable(pixels2), 4):
if color_reduction_method == NEAREST:
(r, g, b, a) = pebble_nearest_color_to_pebble_palette(r, g, b, a)
else:
(r, g, b, a) = pebble_truncate_color_to_pebble_palette(r, g, b, a)
if (r, g, b, a) not in palette:
palette.append((r, g, b, a))
# Check if image contains any transparent pixels
if (a != 0xFF):
has_alpha = True
# greyscale only if rgb is gray and opaque or fully transparent
if is_grey and not (((r == g == b) and a == 255) or (r, g, b, a) == (0, 0, 0, 0)):
is_grey = False
# Calculate required bit depth
if is_grey:
# for Greyscale, it is the required colors that set the bitdepth
# so if image contains LightGray or DarkGray it requires bitdepth 2
if (85, 85, 85, 255) in palette or (170, 170, 170, 255) in palette:
# if palette contains all 4 greyscale and transparent, bump up bitdepth
if (len(palette)) >= 5:
bitdepth = 4
else:
bitdepth = 2
else:
# if palette contains black, white and transparent, bump up bitdepth
if (len(palette)) >= 3:
bitdepth = 2
else:
bitdepth = 1
# determine the grey value for tRNs transparency
if has_alpha:
if bitdepth == 4:
# 4 available shades of grey are occupied
transparent_grey = 0xC # bitdepth 4 supported value
else:
greyscale_list = [0, 255, 85, 170] # in order of bitdepth required
for lum in greyscale_list:
# find the first unused greyscale value in terms of available bitdepth
if (lum, lum, lum, 255) not in palette:
# transparent grey value for requested greyscale bitdepth
transparent_grey = lum >> (8 - bitdepth)
break
else:
# get the bitdepth for the number of colors
bitdepth = num_colors_to_bitdepth(len(palette))
#convert RGBA 32-bit boxed rows to list for output
rgba32_list = grouper(itertools.chain.from_iterable(pixels), 4)
# update data for RGB output format
if not is_grey and not has_alpha:
# recreate the palette without an alpha channel to support RGB PNG
palette = [(p_r, p_g, p_b) for p_r, p_g, p_b, p_a in palette]
# second pass of pixel data, converts rgba32 pixels to greyscale or palettized output
image = []
for (r, g, b, a) in rgba32_list:
# operating on original pixel values, need to do the same color reduction
# as when the palette was generated
if color_reduction_method == NEAREST:
(r, g, b, a) = pebble_nearest_color_to_pebble_palette(r, g, b, a)
else:
(r, g, b, a) = pebble_truncate_color_to_pebble_palette(r, g, b, a)
if is_grey:
# convert red channel (as luminosity value) to a greyscale at bitdepth
# if transparent, output the transparent_grey value for that bitdepth
if a == 0:
image.append(transparent_grey)
else:
image.append(r >> (8 - bitdepth))
elif has_alpha:
# append the palette index for output
image.append(palette.index((r, g, b, a)))
else:
# append the palette index for output
image.append(palette.index((r, g, b)))
if is_grey:
# remove the palette for greyscale output with writer
palette = None
output_png = png.Writer(width=width, height=height, compression=9, bitdepth=bitdepth,
palette=palette, greyscale=is_grey, transparent=transparent_grey)
output_png.write_array(output_file, image)