mirror of https://gitlab.com/bashrc2/epicyon
262 lines
9.7 KiB
Python
262 lines
9.7 KiB
Python
"""
|
|
Copyright (c) 2019 Lorenz Diener
|
|
|
|
Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
of this software and associated documentation files (the "Software"), to deal
|
|
in the Software without restriction, including without limitation the rights
|
|
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
copies of the Software, and to permit persons to whom the Software is
|
|
furnished to do so, subject to the following conditions:
|
|
|
|
* The above copyright notice and this permission notice shall be included in all
|
|
copies or substantial portions of the Software.
|
|
* You and any organization you work for may not promote white supremacy, hate
|
|
speech and homo- or transphobia - this license is void if you do.
|
|
|
|
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
SOFTWARE.
|
|
|
|
https://github.com/halcy/blurhash-python
|
|
|
|
Pure python blurhash decoder with no additional dependencies, for
|
|
both de- and encoding.
|
|
|
|
Very close port of the original Swift implementation by Dag Ågren.
|
|
"""
|
|
|
|
import math
|
|
|
|
# Alphabet for base 83
|
|
alphabet="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#$%*+,-.:;=?@[]^_{|}~"
|
|
alphabet_values=dict(zip(alphabet,range(len(alphabet))))
|
|
|
|
def base83_decode(base83_str):
|
|
"""
|
|
Decodes a base83 string, as used in blurhash, to an integer.
|
|
"""
|
|
value=0
|
|
for base83_char in base83_str:
|
|
value=value*83+alphabet_values[base83_char]
|
|
return value
|
|
|
|
def base83_encode(value, length):
|
|
"""
|
|
Decodes an integer to a base83 string, as used in blurhash.
|
|
|
|
Length is how long the resulting string should be. Will complain
|
|
if the specified length is too short.
|
|
"""
|
|
if int(value) // (83 ** (length)) != 0:
|
|
raise ValueError("Specified length is too short to encode given value.")
|
|
|
|
result=""
|
|
for i in range(1,length+1):
|
|
digit=int(value) // (83 ** (length - i)) % 83
|
|
result += alphabet[int(digit)]
|
|
return result
|
|
|
|
def srgb_to_linear(value):
|
|
"""
|
|
srgb 0-255 integer to linear 0.0-1.0 floating point conversion.
|
|
"""
|
|
value=float(value) / 255.0
|
|
if value <= 0.04045:
|
|
return value / 12.92
|
|
return math.pow((value+0.055) / 1.055, 2.4)
|
|
|
|
def sign_pow(value, exp):
|
|
"""
|
|
Sign-preserving exponentiation.
|
|
"""
|
|
return math.copysign(math.pow(abs(value), exp), value)
|
|
|
|
def linear_to_srgb(value):
|
|
"""
|
|
linear 0.0-1.0 floating point to srgb 0-255 integer conversion.
|
|
"""
|
|
value=max(0.0, min(1.0, value))
|
|
if value <= 0.0031308:
|
|
return int(value*12.92*255+0.5)
|
|
return int((1.055*math.pow(value, 1 / 2.4)-0.055)*255+0.5)
|
|
|
|
def blurhash_components(blurhash):
|
|
"""
|
|
Decodes and returns the number of x and y components in the given blurhash.
|
|
"""
|
|
if len(blurhash) < 6:
|
|
raise ValueError("BlurHash must be at least 6 characters long.")
|
|
|
|
# Decode metadata
|
|
size_info=base83_decode(blurhash[0])
|
|
size_y=int(size_info / 9)+1
|
|
size_x=(size_info % 9)+1
|
|
|
|
return size_x, size_y
|
|
|
|
def blurhash_decode(blurhash,width,height,punch=1.0,linear=False):
|
|
"""
|
|
Decodes the given blurhash to an image of the specified size.
|
|
|
|
Returns the resulting image a list of lists of 3-value sRGB 8 bit integer
|
|
lists. Set linear to True if you would prefer to get linear floating point
|
|
RGB back.
|
|
|
|
The punch parameter can be used to de- or increase the contrast of the
|
|
resulting image.
|
|
|
|
As per the original implementation it is suggested to only decode
|
|
to a relatively small size and then scale the result up, as it
|
|
basically looks the same anyways.
|
|
"""
|
|
if len(blurhash) < 6:
|
|
raise ValueError("BlurHash must be at least 6 characters long.")
|
|
|
|
# Decode metadata
|
|
size_info=base83_decode(blurhash[0])
|
|
size_y=int(size_info / 9)+1
|
|
size_x=(size_info % 9)+1
|
|
|
|
quant_max_value=base83_decode(blurhash[1])
|
|
real_max_value=(float(quant_max_value+1)/166.0)*punch
|
|
|
|
# Make sure we at least have the right number of characters
|
|
if len(blurhash) != 4+2*size_x*size_y:
|
|
raise ValueError("Invalid BlurHash length.")
|
|
|
|
# Decode DC component
|
|
dc_value=base83_decode(blurhash[2:6])
|
|
colours=[(
|
|
srgb_to_linear(dc_value >> 16),
|
|
srgb_to_linear((dc_value >> 8) & 255),
|
|
srgb_to_linear(dc_value & 255)
|
|
)]
|
|
|
|
# Decode AC components
|
|
for component in range(1, size_x * size_y):
|
|
ac_value=base83_decode(blurhash[4+component*2:4+(component+1)*2])
|
|
colours.append((
|
|
sign_pow((float(int(ac_value / (19 * 19))) - 9.0) / 9.0, 2.0) * real_max_value,
|
|
sign_pow((float(int(ac_value / 19) % 19) - 9.0) / 9.0, 2.0) * real_max_value,
|
|
sign_pow((float(ac_value % 19) - 9.0) / 9.0, 2.0) * real_max_value
|
|
))
|
|
|
|
# Return image RGB values, as a list of lists of lists,
|
|
# consumable by something like numpy or PIL.
|
|
pixels=[]
|
|
for y in range(height):
|
|
pixel_row=[]
|
|
for x in range(width):
|
|
pixel=[0.0, 0.0, 0.0]
|
|
|
|
for j in range(size_y):
|
|
for i in range(size_x):
|
|
basis= \
|
|
math.cos(math.pi*float(x)*float(i)/float(width))* \
|
|
math.cos(math.pi*float(y)*float(j)/float(height))
|
|
colour=colours[i+j*size_x]
|
|
pixel[0] += colour[0]*basis
|
|
pixel[1] += colour[1]*basis
|
|
pixel[2] += colour[2]*basis
|
|
if linear == False:
|
|
pixel_row.append([
|
|
linear_to_srgb(pixel[0]),
|
|
linear_to_srgb(pixel[1]),
|
|
linear_to_srgb(pixel[2]),
|
|
])
|
|
else:
|
|
pixel_row.append(pixel)
|
|
pixels.append(pixel_row)
|
|
return pixels
|
|
|
|
def blurhash_encode(image,components_x=4,components_y=4,linear=False):
|
|
"""
|
|
Calculates the blurhash for an image using the given x and y component counts.
|
|
|
|
Image should be a 3-dimensional array, with the first dimension being y, the second
|
|
being x, and the third being the three rgb components that are assumed to be 0-255
|
|
srgb integers (incidentally, this is the format you will get from a PIL RGB image).
|
|
|
|
You can also pass in already linear data - to do this, set linear to True. This is
|
|
useful if you want to encode a version of your image resized to a smaller size (which
|
|
you should ideally do in linear colour).
|
|
"""
|
|
if components_x < 1 or components_x > 9 or components_y < 1 or components_y > 9:
|
|
raise ValueError("x and y component counts must be between 1 and 9 inclusive.")
|
|
height=float(len(image))
|
|
width=float(len(image[0]))
|
|
|
|
# Convert to linear if neeeded
|
|
image_linear=[]
|
|
if linear==False:
|
|
for y in range(int(height)):
|
|
image_linear_line=[]
|
|
for x in range(int(width)):
|
|
image_linear_line.append([
|
|
srgb_to_linear(image[y][x][0]),
|
|
srgb_to_linear(image[y][x][1]),
|
|
srgb_to_linear(image[y][x][2])
|
|
])
|
|
image_linear.append(image_linear_line)
|
|
else:
|
|
image_linear=image
|
|
|
|
# Calculate components
|
|
components=[]
|
|
max_ac_component=0.0
|
|
for j in range(components_y):
|
|
for i in range(components_x):
|
|
norm_factor=1.0 if (i==0 and j==0) else 2.0
|
|
component=[0.0,0.0,0.0]
|
|
for y in range(int(height)):
|
|
for x in range(int(width)):
|
|
basis= \
|
|
norm_factor * math.cos(math.pi * float(i) * float(x) / width) * \
|
|
math.cos(math.pi * float(j) * float(y) / height)
|
|
component[0] += basis * image_linear[y][x][0]
|
|
component[1] += basis * image_linear[y][x][1]
|
|
component[2] += basis * image_linear[y][x][2]
|
|
|
|
component[0] /= (width * height)
|
|
component[1] /= (width * height)
|
|
component[2] /= (width * height)
|
|
components.append(component)
|
|
|
|
if not (i==0 and j==0):
|
|
max_ac_component= \
|
|
max(max_ac_component,abs(component[0]), \
|
|
abs(component[1]),abs(component[2]))
|
|
|
|
# Encode components
|
|
dc_value= \
|
|
(linear_to_srgb(components[0][0]) << 16)+ \
|
|
(linear_to_srgb(components[0][1]) << 8)+ \
|
|
linear_to_srgb(components[0][2])
|
|
|
|
quant_max_ac_component= \
|
|
int(max(0, min(82, math.floor(max_ac_component * 166 - 0.5))))
|
|
ac_component_norm_factor= \
|
|
float(quant_max_ac_component+1) / 166.0
|
|
|
|
ac_values=[]
|
|
for r, g, b in components[1:]:
|
|
ac_values.append(
|
|
int(max(0.0,min(18.0,math.floor(sign_pow(r / ac_component_norm_factor, 0.5) * 9.0 + 9.5)))) * 19 * 19 + \
|
|
int(max(0.0,min(18.0, math.floor(sign_pow(g / ac_component_norm_factor, 0.5) * 9.0 + 9.5)))) * 19 + \
|
|
int(max(0.0,min(18.0, math.floor(sign_pow(b / ac_component_norm_factor, 0.5) * 9.0 + 9.5))))
|
|
)
|
|
|
|
# Build final blurhash
|
|
blurhash=""
|
|
blurhash += base83_encode((components_x - 1) + (components_y - 1) * 9, 1)
|
|
blurhash += base83_encode(quant_max_ac_component, 1)
|
|
blurhash += base83_encode(dc_value, 4)
|
|
for ac_value in ac_values:
|
|
blurhash += base83_encode(ac_value, 2)
|
|
|
|
return blurhash
|