imageanalyzer/section.py

   1 #!/usr/bin/env python
   2 # -*- coding: UTF8 -*-
   3 #
   4 #   Copyright (C) 2006-2007 Antonio Ingargiola <tritemio@gmail.com>
   5 #
   6 #   This file is part of Image Analyzer.
   7 #
   8 #   Image Analyzer is free software; you can redistribute it and/or modify
   9 #   it under the terms of the GNU General Public License as published by
  10 #   the Free Software Foundation; either version 2 of the License, or
  11 #   (at your option) any later version.
  12
  13
  14 from numpy import arange, sign, array, sqrt
  15
  16 def rounda(array):
  17     """Round the array passed to the nearest integer."""
  18     return floor(array + 0.5).astype('int32')
  19
  20 class ArraySection:
  21     """
  22     Class representing an array section. See the __init__ documetation.
  23     """
  24     def __init__(self, arr, x1, x2, y1, y2, xPixDim, yPixDim, debug=False):
  25         """
  26         Parameters
  27         arr:    arrray to section
  28         x1, x2,
  29         y1, y2: coordinates of the twop point indentifing the segment
  30                 along which to calculate the array values (the section).
  31                 This params are in array-index coordinates.
  32         xPixDim,
  33         yPixDim: X and Y dimention of one pixel (element) of the array
  34         debug:  optionally enable debug prints
  35
  36         Class Attributes:
  37         self.y: the array values along the section
  38         self.x: the X axis for self.y calculated considering the effective
  39                 section length (considering pixel dimetion and the slope).
  40         self.dim: real section length calculated based on pixel dimention and
  41                   section slope.
  42         self.color: Default to None, you can fill this to associate a color
  43                     to the section
  44         """
  45         # Calculate section values
  46         self.y = sectionarray(arr, x1, x2, y1, y2, debug=debug)
  47         self.dim = sqrt( ((x2-x1)*xPixDim)**2 + ((y2-y1)*yPixDim)**2 )
  48         self.x = arange(len(self.y))/float(len(self.y)-1) * self.dim
  49
  50         # The caller can use this
  51         self.color = None
  52
  53         ## Save some data about the segment
  54         #self.x1, self.x2, self.y1, self.y2, self.xPixDim, self.yPixDim =\
  55         #        x1, x2, y1, y2, xPixDim, yPixDim
  56
  57         # Provided for further extensions (currently unused)
  58         #self.plotkwargs = dict()
  59
  60
  61 def sectionarray(arr, x1, x2, y1, y2, debug=False):
  62     """
  63     Returns the pixel-precise section of the array between the two points (x1,
  64     y1) and (x2, y2) (extremezes included).
  65
  66     """
  67     dx = x2 - x1
  68     dy = y2 - y1
  69     n = max(abs(dx),abs(dy))
  70     if debug: print 'dx:', dx, 'dy:', dy, 'n:', n
  71
  72     if dx == 0 and dy == 0:
  73         # Single point
  74         if debug: print 'point segment'
  75         section = arr[x1, y1]
  76     elif dx == 0:
  77         # Vertical segment
  78         if debug: print 'vertical segment'
  79         y = arange(y1, y2+sign(dy), sign(dy))
  80         section = arr[y, x1]
  81     elif dy == 0:
  82         # Horizzontal segment
  83         if debug: print 'orizzontale segment'
  84         x = arange(x1, x2+sign(dx), sign(dx))
  85         section = arr[y1, x]
  86     else:
  87         # Skew segment
  88         if debug: print 'skew segment'
  89         m = float(dy) / float(dx)
  90         c = y1 - m*x1
  91         step = float(dx) / float(n)
  92         if debug: print 'm:',m,'c:',c,'step:',step
  93         X = arange(x1, x2+step, step)
  94         Y = m * X + c
  95
  96         arr = array(arr)
  97         section = arr[Y.round().astype('uint'), X.round().astype('uint')]
  98
  99     return section
 100
 101 if __name__ == "__main__":
 102     from scipy import lena
 103     from pylab import plot, imshow, title, grid, gcf, gca, show, draw
 104     l = lena()
 105     imshow(l)
 106     title('Click on two points the close the window')
 107
 108     points = []
 109     def button_press_callback(event):
 110         points.append([event.xdata, event.ydata])
 111         gca().plot((event.xdata,), (event.ydata,), 'k', marker='.', ms=10)
 112         draw()
 113
 114     gcf().canvas.mpl_connect('button_press_event', button_press_callback)
 115     show()
 116
 117     c = ArraySection(l,
 118             points[-2][0], points[-1][0],
 119             points[-2][1], points[-1][1], 1, 1)
 120
 121     plot(c.x, c.y, '-b.', linewidth=1, ms=10)
 122     title('Image section')
 123     grid(True)
 124     show()
 125
 126
 127
 128
 129