def make_grayscale(img: ImageType) -> ImageType:
""" Convert an Image to grayscale
:param img: a PIL image in color (modes P, RGBA, RGB, CMYK, YCbCr, LAB or HSV)
:return: a PIL image object in modes P, L or RGBA, if converted, or the
original Image object in case no conversion is done.
"""
orig_mode = img.mode
if orig_mode in ["RGB", "CMYK", "YCbCr", "LAB", "HSV"]:
return img.convert("L")
elif orig_mode == "RGBA":
return img.convert("LA").convert("RGBA")
elif orig_mode == "P":
# Using ITU-R 601-2 luma transform: L = R * 299/1000 + G * 587/1000 + B * 114/1000
pal = img.getpalette()
for i in range(len(pal) // 3):
# Using ITU-R 601-2 luma transform
g = (pal[3 * i] * 299 + pal[3 * i + 1] * 587 +
pal[3 * i + 2] * 114) // 1000
pal[3 * i:3 * i + 3] = [g, g, g]
img.putpalette(pal)
return img
else:
return img
def do_reduce_colors(img: ImageType,
max_colors: int) -> Tuple[ImageType, int, int]:
""" Reduce the number of colors of an Image object
It takes a PIL image object and tries to reduce the total number of colors,
converting it to an indexed color (mode P) image. If the input image is in
mode 1, it cannot be further reduced, so it's returned back with no
changes.
:param img: a PIL image in color (modes P, RGBA, RGB, CMYK, YCbCr, LAB or HSV)
:param max_colors: an integer indicating the maximum number of colors allowed.
:return: a PIL image in mode P (or mode 1, as stated above), an integer
indicating the original number of colors (0 if source is not a
mode P or mode 1 image) and an integer stating the resulting
number of colors.
"""
orig_mode = img.mode
if orig_mode == "1":
return img, 2, 2
colors = img.getcolors()
if colors:
orig_colors = len(colors)
else:
orig_colors = 0
# Intermediate conversion steps when needed
if orig_mode in ["CMYK", "YCbCr", "LAB", "HSV"]:
img = img.convert("RGB")
elif orig_mode == "LA":
img = img.convert("RGBA")
# Actual color reduction happening here
if orig_mode in ["RGB", "L"]:
palette = Image.ADAPTIVE
elif orig_mode == "RGBA":
palette = Image.ADAPTIVE
transparent = Image.new("RGBA", img.size, (0, 0, 0, 0))
# blend with transparent image using own alpha
img = Image.composite(img, transparent, img)
elif orig_mode == "P":
palette = img.getpalette()
img = img.convert("RGBA")
w, h = img.size
alpha_layer = Image.new("L", img.size)
for x in range(w):
for y in range(h):
r, g, b, a = img.getpixel((x, y))
alpha_layer.putpixel((x, y), a)
img.putalpha(alpha_layer)
else:
return img, 0, 0
img = img.convert("P", palette=palette, colors=max_colors)
return img, orig_colors, len(img.getcolors())
def remove_transparency(img: ImageType,
bg_color=DEFAULT_BG_COLOR) -> ImageType:
"""Remove alpha transparency from PNG images
Expects a PIL.Image object and returns an object of the same type with the
changes applied.
Special thanks to Yuji Tomita and Takahashi Shuuji
(https://stackoverflow.com/a/33507138)
"""
if img.mode in ('RGBA', 'LA') or (img.mode == 'P'
and 'transparency' in img.info):
orig_image = img.convert('RGBA')
background = Image.new('RGBA', orig_image.size, bg_color)
img = Image.alpha_composite(background, orig_image)
return img.convert("RGB")
else:
return img
def downsize_img(img: ImageType, max_w: int,
max_h: int) -> Tuple[ImageType, bool]:
""" Reduce the size of an image to the indicated maximum dimensions
This function takes a PIL.Image object and integer values for the maximum
allowed width and height (a zero value means no maximum constraint),
calculates the size that meets those constraints and resizes the image. The
resize is done in place, changing the original object. Returns a boolean
indicating if the image was changed.
"""
w, h = img.size
# Assume 0 as current size
if not max_w:
max_w = w
if not max_h:
max_h = h
if (max_w, max_h) == (w, h): # If no changes, do nothing
return img, False
img.thumbnail((max_w, max_h), resample=Image.LANCZOS)
return img, True
def rebuild_palette(img: ImageType) -> Tuple[ImageType, int]:
""" Rebuild the palette of a mode "P" PNG image
It may allow for other tools, like PNGOUT and AdvPNG, to further reduce the
size of some indexed PNG images. However, it it was already an optimized PNG,
the resulting file size may in fact be bigger (which means optimize-images
may discard it by default). You may also want to use it as an intermediate
process, before doing a final optimization using those tools.
:param img: a mode "P" PNG image
:return: a tuple composed by a mode "P" PNG image object and an integer
with the resulting number of colors
"""
w, h = img.size
img = img.convert("RGBA")
new_palette = Palette()
alpha_layer = Image.new("L", img.size)
for x in range(w):
for y in range(h):
r, g, b, a = img.getpixel((x, y))
alpha_layer.putpixel((x, y), a)
new_palette.add(r, g, b)
img.putalpha(alpha_layer)
palette = new_palette.get_palette()
num_colors = len(palette) // 3
img = img.convert("P", palette=palette, colors=num_colors)
return img, len(img.getcolors())