#

# Python Imaging Library

# $Id$

#

# stuff to read (and render) GIMP gradient files

#

# History:

# 97-08-23 fl Created

#

# Copyright (c) Secret Labs AB 1997.

# Copyright (c) Fredrik Lundh 1997.

#

# See the README file for information on usage and redistribution.

#

"""

Stuff to translate curve segments to palette values (derived from

the corresponding code in GIMP, written by Federico Mena Quintero.

See the GIMP distribution for more information.)

"""

from __future__ import annotations

from math import log, pi, sin, sqrt

from ._binary import o8

TYPE_CHECKING = False

if TYPE_CHECKING:

from collections.abc import Callable

from typing import IO

EPSILON = 1e-10

"""""" # Enable auto-doc for data member

def linear(middle: float, pos: float) -> float:

if pos <= middle:

if middle < EPSILON:

return 0.0

else:

return 0.5 * pos / middle

else:

pos = pos - middle

middle = 1.0 - middle

if middle < EPSILON:

return 1.0

else:

return 0.5 + 0.5 * pos / middle

def curved(middle: float, pos: float) -> float:

return pos ** (log(0.5) / log(max(middle, EPSILON)))

def sine(middle: float, pos: float) -> float:

return (sin((-pi / 2.0) + pi * linear(middle, pos)) + 1.0) / 2.0

def sphere_increasing(middle: float, pos: float) -> float:

return sqrt(1.0 - (linear(middle, pos) - 1.0) ** 2)

def sphere_decreasing(middle: float, pos: float) -> float:

return 1.0 - sqrt(1.0 - linear(middle, pos) ** 2)

SEGMENTS = [linear, curved, sine, sphere_increasing, sphere_decreasing]

"""""" # Enable auto-doc for data member

class GradientFile:

gradient: (

list[

tuple[

float,

float,

float,

list[float],

list[float],

Callable[[float, float], float],

]

]

| None

) = None

def getpalette(self, entries: int = 256) -> tuple[bytes, str]:

assert self.gradient is not None

palette = []

ix = 0

x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix]

for i in range(entries):

x = i / (entries - 1)

while x1 < x:

ix += 1

x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix]

w = x1 - x0

if w < EPSILON:

scale = segment(0.5, 0.5)

else:

scale = segment((xm - x0) / w, (x - x0) / w)

# expand to RGBA

r = o8(int(255 * ((rgb1[0] - rgb0[0]) * scale + rgb0[0]) + 0.5))

g = o8(int(255 * ((rgb1[1] - rgb0[1]) * scale + rgb0[1]) + 0.5))

b = o8(int(255 * ((rgb1[2] - rgb0[2]) * scale + rgb0[2]) + 0.5))

a = o8(int(255 * ((rgb1[3] - rgb0[3]) * scale + rgb0[3]) + 0.5))

# add to palette

palette.append(r + g + b + a)

return b"".join(palette), "RGBA"

class GimpGradientFile(GradientFile):

"""File handler for GIMP's gradient format."""

def __init__(self, fp: IO[bytes]) -> None:

if not fp.readline().startswith(b"GIMP Gradient"):

msg = "not a GIMP gradient file"

raise SyntaxError(msg)

line = fp.readline()

# GIMP 1.2 gradient files don't contain a name, but GIMP 1.3 files do

if line.startswith(b"Name: "):

line = fp.readline().strip()

count = int(line)

self.gradient = []

for i in range(count):

s = fp.readline().split()

w = [float(x) for x in s[:11]]

x0, x1 = w[0], w[2]

xm = w[1]

rgb0 = w[3:7]

rgb1 = w[7:11]

segment = SEGMENTS[int(s[11])]

cspace = int(s[12])

if cspace != 0:

msg = "cannot handle HSV colour space"

raise OSError(msg)

self.gradient.append((x0, x1, xm, rgb0, rgb1, segment))