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3f14341629
Instead of being a copy of line 76, line 79 instead correctly indicates that it will show a histogram for a gray image in curve mode, as given by the code block at line 103 referencing image "gray" instead of image "im".
126 lines
3.6 KiB
Python
Executable File
126 lines
3.6 KiB
Python
Executable File
#!/usr/bin/env python
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''' This is a sample for histogram plotting for RGB images and grayscale images for better understanding of colour distribution
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Benefit : Learn how to draw histogram of images
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Get familier with cv.calcHist, cv.equalizeHist,cv.normalize and some drawing functions
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Level : Beginner or Intermediate
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Functions : 1) hist_curve : returns histogram of an image drawn as curves
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2) hist_lines : return histogram of an image drawn as bins ( only for grayscale images )
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Usage : python hist.py <image_file>
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Abid Rahman 3/14/12 debug Gary Bradski
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'''
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# Python 2/3 compatibility
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from __future__ import print_function
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import numpy as np
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import cv2 as cv
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bins = np.arange(256).reshape(256,1)
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def hist_curve(im):
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h = np.zeros((300,256,3))
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if len(im.shape) == 2:
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color = [(255,255,255)]
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elif im.shape[2] == 3:
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color = [ (255,0,0),(0,255,0),(0,0,255) ]
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for ch, col in enumerate(color):
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hist_item = cv.calcHist([im],[ch],None,[256],[0,256])
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cv.normalize(hist_item,hist_item,0,255,cv.NORM_MINMAX)
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hist=np.int32(np.around(hist_item))
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pts = np.int32(np.column_stack((bins,hist)))
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cv.polylines(h,[pts],False,col)
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y=np.flipud(h)
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return y
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def hist_lines(im):
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h = np.zeros((300,256,3))
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if len(im.shape)!=2:
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print("hist_lines applicable only for grayscale images")
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#print("so converting image to grayscale for representation"
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im = cv.cvtColor(im,cv.COLOR_BGR2GRAY)
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hist_item = cv.calcHist([im],[0],None,[256],[0,256])
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cv.normalize(hist_item,hist_item,0,255,cv.NORM_MINMAX)
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hist=np.int32(np.around(hist_item))
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for x,y in enumerate(hist):
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cv.line(h,(x,0),(x,y),(255,255,255))
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y = np.flipud(h)
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return y
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def main():
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import sys
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if len(sys.argv)>1:
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fname = sys.argv[1]
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else :
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fname = 'lena.jpg'
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print("usage : python hist.py <image_file>")
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im = cv.imread(cv.samples.findFile(fname))
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if im is None:
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print('Failed to load image file:', fname)
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sys.exit(1)
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gray = cv.cvtColor(im,cv.COLOR_BGR2GRAY)
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print(''' Histogram plotting \n
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Keymap :\n
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a - show histogram for color image in curve mode \n
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b - show histogram in bin mode \n
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c - show equalized histogram (always in bin mode) \n
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d - show histogram for gray image in curve mode \n
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e - show histogram for a normalized image in curve mode \n
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Esc - exit \n
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''')
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cv.imshow('image',im)
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while True:
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k = cv.waitKey(0)
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if k == ord('a'):
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curve = hist_curve(im)
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cv.imshow('histogram',curve)
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cv.imshow('image',im)
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print('a')
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elif k == ord('b'):
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print('b')
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lines = hist_lines(im)
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cv.imshow('histogram',lines)
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cv.imshow('image',gray)
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elif k == ord('c'):
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print('c')
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equ = cv.equalizeHist(gray)
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lines = hist_lines(equ)
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cv.imshow('histogram',lines)
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cv.imshow('image',equ)
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elif k == ord('d'):
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print('d')
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curve = hist_curve(gray)
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cv.imshow('histogram',curve)
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cv.imshow('image',gray)
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elif k == ord('e'):
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print('e')
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norm = cv.normalize(gray, gray, alpha = 0,beta = 255,norm_type = cv.NORM_MINMAX)
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lines = hist_lines(norm)
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cv.imshow('histogram',lines)
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cv.imshow('image',norm)
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elif k == 27:
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print('ESC')
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cv.destroyAllWindows()
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break
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print('Done')
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if __name__ == '__main__':
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print(__doc__)
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main()
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cv.destroyAllWindows()
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