# -*- coding: utf-8 -*-
from PIL import Image
from pylab import *
from numpy import *
import os

def process_image(imagename, resultname, params="--edge-thresh 10 --peak-thresh 5"):
    """ 處理一幅影象，然後將結果儲存在檔案中"""

    if imagename[-3:] != 'pgm':
        #建立一個pgm檔案
        im = Image.open(imagename).convert('L')
        im.save('tmp.pgm')
        imagename ='tmp.pgm'
    cmmd = str("sift "+imagename+" --output="+resultname+" "+params)
    os.system(cmmd)
    print(cmmd)
    print ('processed', imagename, 'to', resultname)

def read_features_from_file(filename):
    """讀取特徵屬性值，然後將其以矩陣的形式返回"""
    f = loadtxt(filename)
    return f[:,:4], f[:,4:] #特徵位置，描述子

def write_featrues_to_file(filename, locs, desc):
    """將特徵位置和描述子儲存到檔案中"""
    savetxt(filename, hstack((locs,desc)))

def plot_features(im, locs, circle=False):
    """顯示帶有特徵的影象
       輸入：im（陣列影象），locs（每個特徵的行、列、尺度和朝向）"""

    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')

imname = 'D:\mywindows\Python Sample\hx.jpg'
im1 = array(Image.open(imname).convert('L'))
process_image(imname, 'img.sift')
l1,d1 = read_features_from_file('img.sift')

figure()
gray()
plot_features(im1, l1, circle=True)
show()