Source code for PIL.GimpGradientFile

#
# 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.
#

from math import log, pi, sin, sqrt

from ._binary import o8

# --------------------------------------------------------------------
# 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.)
#

EPSILON = 1e-10


[docs]def linear(middle, pos): 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, pos): return pos ** (log(0.5) / log(max(middle, EPSILON)))
[docs]def sine(middle, pos): return (sin((-pi / 2.0) + pi * linear(middle, pos)) + 1.0) / 2.0
[docs]def sphere_increasing(middle, pos): return sqrt(1.0 - (linear(middle, pos) - 1.0) ** 2)
[docs]def sphere_decreasing(middle, pos): return 1.0 - sqrt(1.0 - linear(middle, pos) ** 2)
SEGMENTS = [linear, curved, sine, sphere_increasing, sphere_decreasing]
[docs]class GradientFile: gradient = None
[docs] def getpalette(self, entries=256): palette = [] ix = 0 x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix] for i in range(entries): x = i / float(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"
## # File handler for GIMP's gradient format.
[docs]class GimpGradientFile(GradientFile): def __init__(self, fp): if fp.readline()[:13] != b"GIMP Gradient": raise SyntaxError("not a GIMP gradient file") 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) 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: raise OSError("cannot handle HSV colour space") gradient.append((x0, x1, xm, rgb0, rgb1, segment)) self.gradient = gradient