PIL获取图片RGB值时只能获取一个值

im1=Image.open('1.gif')
print im1.getpixel((50,50))

返回的是一个

注：图片的mode时p

im1 = Image.open('1.gif')
pix = im1.load()
width = im1.size[0]
height = im1.size[1]
for x in range(width):
for y in range(height):
r, g, b = pix[x, y]
....