imshow(A,[])和imshow(A)的区别

imshow的用法：

IMSHOW Display image.
    IMSHOW(I,N) displays the intensity image I with N discrete
    levels of gray. If you omit N, IMSHOW uses 256 gray levels on
    24-bit displays, or 64 gray levels on other systems.
IMSHOW(I,N)显示强度图像I，使用N个离散灰度级别。如果你省略N，IMSHOW使用256灰度级别。
    IMSHOW(I,[LOW HIGH]) displays I as a grayscale intensity
    image, specifying the data range for I. The value LOW (and
    any value less than LOW) displays as black, the value HIGH
    (and any value greater than HIGH) displays as white, and
    values in between display as intermediate shades of
    gray. IMSHOW uses the default number of gray levels. If you
    use an empty matrix ([]) for [LOW HIGH], IMSHOW uses
    [min(I(:)) max(I(:))]; the minimum value in I displays as
    black, and the maximum value displays as white.
    将图像I显示为一个灰度级强度图像，并且指定I的数据范围。值LOW（以及任何比LOW低的值）显示为黑，值HIGH（以及任何高于HIGH的值）显示为白，并且二者之间的值显示为灰度的中间色调。如果为[LOW HIGH]使用一个空的矩阵（[]）,那么IMSHOW就使用 [min(I(:)) max(I(:))];I中的最小值展示为黑，最大值展示为白。

    IMSHOW(BW) displays the binary image BW. Values of 0 display
    as black, and values of 1 display as white.
 
    IMSHOW(X,MAP) displays the indexed image X with the colormap
    MAP.
 
    IMSHOW(RGB) displays the truecolor image RGB.
 
    IMSHOW(...,DISPLAY_OPTION) displays the image, calling
    TRUESIZE if DISPLAY_OPTION is 'truesize', or suppressing the
    call to TRUESIZE if DISPLAY_OPTION is 'notruesize'. Either
    option string can be abbreviated. If you do not supply this
    argument, IMSHOW determines whether to call TRUESIZE based on
    the setting of the 'ImshowTruesize' preference.