im2 = imageio.imread(filename)
Nix=im2.shape[0]
Niy=im2.shape[1]
grayimage=np.zeros([Nix,Niy])
for i in range(0,Nix):
        for j in range(0,Niy):
            blueComponent = im2[i][j][0]
            greenComponent = im2[i][j][1]
            redComponent = im2[i][j][2]
            grayValue = 0.07 * blueComponent + 0.72 * greenComponent + 0.21 * redComponent
            grayimage[i][j] = grayValue
            pass
dsqin=1-grayimage/255.0
hsimage=plt.imshow(dsqin,cmap='Greys',aspect=1,interpolation='none')
plt.colorbar(hsimage)
plt.show(hsimage)