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# # 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 typing import IO, Callable from ._binary import o8 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))