Python OpenCV处理图像之图像直方图和反向投影


            本文实例为大家分享了Python OpenCV图像直方图和反向投影的具体代码，供大家参考，具体内容如下

当我们想比较两张图片相似度的时候，可以使用这一节提到的技术

直方图对比

反向投影

关于这两种技术的原理可以参考我上面贴的链接，下面是示例的代码：

0x01. 绘制直方图





import cv2.cv as cv

 

def drawGraph(ar,im, size): #Draw the histogram on the image

  minV, maxV, minloc, maxloc = cv.MinMaxLoc(ar) #Get the min and max value

  hpt = 0.9 * histsize

  for i in range(size):

    intensity = ar[i] * hpt / maxV #Calculate the intensity to make enter in the image

    cv.Line(im, (i,size), (i,int(size-intensity)),cv.Scalar(255,255,255)) #Draw the line

    i += 1

 

#---- Gray image

orig = cv.LoadImage("img/lena.jpg", cv.CV_8U)

 

histsize = 256 #Because we are working on grayscale pictures which values within 0-255

 

hist = cv.CreateHist([histsize], cv.CV_HIST_ARRAY, [[0,histsize]], 1)

 

cv.CalcHist([orig], hist) #Calculate histogram for the given grayscale picture

 

histImg = cv.CreateMat(histsize, histsize, cv.CV_8U) #Image that will contain the graph of the repartition of values

drawGraph(hist.bins, histImg, histsize)

 

cv.ShowImage("Original Image", orig)

cv.ShowImage("Original Histogram", histImg)

#---------------------

 

#---- Equalized image

imEq = cv.CloneImage(orig)

cv.EqualizeHist(imEq, imEq) #Equlize the original image

 

histEq = cv.CreateHist([histsize], cv.CV_HIST_ARRAY, [[0,histsize]], 1)

cv.CalcHist([imEq], histEq) #Calculate histogram for the given grayscale picture

eqImg = cv.CreateMat(histsize, histsize, cv.CV_8U) #Image that will contain the graph of the repartition of values

drawGraph(histEq.bins, eqImg, histsize)

 

cv.ShowImage("Image Equalized", imEq)

cv.ShowImage("Equalized HIstogram", eqImg)

#--------------------------------

 

cv.WaitKey(0)



0x02. 反向投影





import cv2.cv as cv

 

im = cv.LoadImage("img/lena.jpg", cv.CV_8U)

 

cv.SetImageROI(im, (1, 1,30,30))

 

histsize = 256 #Because we are working on grayscale pictures

hist = cv.CreateHist([histsize], cv.CV_HIST_ARRAY, [[0,histsize]], 1)

cv.CalcHist([im], hist)

 

 

cv.NormalizeHist(hist,1) # The factor rescale values by multiplying values by the factor

_,max_value,_,_ = cv.GetMinMaxHistValue(hist)

 

if max_value == 0:

  max_value = 1.0

cv.NormalizeHist(hist,256/max_value)

 

cv.ResetImageROI(im)

 

res = cv.CreateMat(im.height, im.width, cv.CV_8U)

cv.CalcBackProject([im], res, hist)

 

cv.Rectangle(im, (1,1), (30,30), (0,0,255), 2, cv.CV_FILLED)

cv.ShowImage("Original Image", im)

cv.ShowImage("BackProjected", res)

cv.WaitKey(0)



以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持中文源码网。