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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 math import log, pi, sin, sqrt | |
| from ._binary import o8 | |
| EPSILON = 1e-10 | |
| """""" # Enable auto-doc for data member | |
| 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 | |
| def curved(middle, pos): | |
| return pos ** (log(0.5) / log(max(middle, EPSILON))) | |
| def sine(middle, pos): | |
| return (sin((-pi / 2.0) + pi * linear(middle, pos)) + 1.0) / 2.0 | |
| def sphere_increasing(middle, pos): | |
| return sqrt(1.0 - (linear(middle, pos) - 1.0) ** 2) | |
| def sphere_decreasing(middle, pos): | |
| 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 = None | |
| def getpalette(self, entries=256): | |
| 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): | |
| if fp.readline()[:13] != 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) | |
| 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) | |
| gradient.append((x0, x1, xm, rgb0, rgb1, segment)) | |
| self.gradient = gradient | |