Pillow (PIL Fork) 11.3.0.dev0 documentation (original) (raw)

Python Imaging Library

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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 typing import IO, Callable

from ._binary import o8

EPSILON = 1e-10 """""" # Enable auto-doc for data member

[docs] 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

[docs] def curved(middle: float, pos: float) -> float: return pos ** (log(0.5) / log(max(middle, EPSILON)))

[docs] def sine(middle: float, pos: float) -> float: return (sin((-pi / 2.0) + pi * linear(middle, pos)) + 1.0) / 2.0

[docs] def sphere_increasing(middle: float, pos: float) -> float: return sqrt(1.0 - (linear(middle, pos) - 1.0) ** 2)

[docs] 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

[docs] class GradientFile: gradient: ( list[ tuple[ float, float, float, list[float], list[float], Callable[[float, float], float], ] ] | None ) = None

[docs] 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"

[docs] 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))