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#!/usr/bin/python
from opencv.cv import *
from opencv.highgui import *
import sys
file_name = "../c/baboon.jpg";
_brightness = 100
_contrast = 100
Gbrightness = 100
Gcontrast = 100
hist_size = 64
range_0=[0,256]
ranges = [ range_0 ]
src_image=None
dst_image=None
hist_image=None
hist=None
lut=cvCreateMat(256,1,CV_8U)
# brightness/contrast callback function
def update_brightness( val ):
global Gbrightness # global tag is required, or we get UnboundLocalError
Gbrightness = val
update_brightcont( )
def update_contrast( val ):
global Gcontrast # global tag is required, or we get UnboundLocalError
Gcontrast = val
update_brightcont( )
def update_brightcont():
# no global tag required for images ???
brightness = Gbrightness - 100;
contrast = Gcontrast - 100;
max_value = 0;
# The algorithm is by Werner D. Streidt
# (http://visca.com/ffactory/archives/5-99/msg00021.html)
if( contrast > 0 ):
delta = 127.*contrast/100;
a = 255./(255. - delta*2);
b = a*(brightness - delta);
else:
delta = -128.*contrast/100;
a = (256.-delta*2)/255.;
b = a*brightness + delta;
for i in range(256):
v = cvRound(a*i + b);
if( v < 0 ):
v = 0;
if( v > 255 ):
v = 255;
lut[i] = v;
cvLUT( src_image, dst_image, lut );
cvShowImage( "image", dst_image );
cvCalcHist( dst_image, hist, 0, None );
cvZero( dst_image );
min_value, max_value = cvGetMinMaxHistValue( hist );
cvScale( hist.bins, hist.bins, float(hist_image.height)/max_value, 0 );
#cvNormalizeHist( hist, 1000 );
cvSet( hist_image, cvScalarAll(255));
bin_w = cvRound(float(hist_image.width)/hist_size);
for i in range(hist_size):
cvRectangle( hist_image, cvPoint(i*bin_w, hist_image.height),
cvPoint((i+1)*bin_w, hist_image.height - cvRound(cvGetReal1D(hist.bins,i))),
cvScalarAll(0), -1, 8, 0 );
cvShowImage( "histogram", hist_image );
if __name__ == "__main__":
# Load the source image. HighGUI use.
if len(sys.argv)>1:
file_name = sys.argv[1]
src_image = cvLoadImage( file_name, 0 );
if not src_image:
print "Image was not loaded.";
sys.exit(-1)
dst_image = cvCloneImage(src_image);
hist_image = cvCreateImage(cvSize(320,200), 8, 1);
hist = cvCreateHist([hist_size], CV_HIST_ARRAY, ranges, 1);
cvNamedWindow("image", 0);
cvNamedWindow("histogram", 0);
cvCreateTrackbar("brightness", "image", _brightness, 200, update_brightness);
cvCreateTrackbar("contrast", "image", _contrast, 200, update_contrast);
update_brightcont();
cvWaitKey(0);
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