sift.py

from PIL import Image
from numpy import *
from pylab import *
import os

def process_image(imagename,resultname,params="--edge-thresh 10 --peak-thresh 5"):
    """ Process an image and save the results in a file. """

    if imagename[-3:] != 'pgm':
        # create a pgm file
        im = Image.open(imagename).convert('L')  #.convert('L') 将RGB图像转为灰度模式，灰度值范围[0,255]
        im.save('tmp.pgm')                       #将灰度值图像信息保存在.pgm文件中
        imagename = 'tmp.pgm'
   
    cmmd = str("E:\code\Sift\sift_python\sift.exe "+imagename+" --output="+resultname+
                " "+params)
    os.system(cmmd)                              #执行sift可执行程序，生成resultname(test.sift)文件
    print 'processed', imagename, 'to', resultname


def read_features_from_file(filename):
    """ Read feature properties and return in matrix form. """
    
    f = loadtxt(filename)
    return f[:,:4],f[:,4:] # feature locations, descriptors


def plot_features(im,locs,circle=True):
    """ Show image with features. input: im (image as array), 
        locs (row, col, scale, orientation of each feature). """

    def draw_circle(c,r):
        t = arange(0,1.01,.01)*2*pi
        x = r*cos(t) + c[0]
        y = r*sin(t) + c[1]
        plot(x,y,'b',linewidth=2)

    imshow(im)
    if circle:
        for p in locs:
            draw_circle(p[:2],p[2]) 
    else:
        plot(locs[:,0],locs[:,1],'ob')
    axis('off')

 

if __name__ == '__main__':
    imname = ('E:\\code\\Sift\\library.jpg')               #待处理图像路径
    im=Image.open(imname)
    process_image(imname,'test.sift')
    l1,d1 = read_features_from_file('test.sift')           #l1为兴趣点坐标、尺度和方位角度 l2是对应描述符的128 维向
    figure()
    gray()
    plot_features(im,l1,circle = True)
    title('sift-features')
    show()