dataset.py 文件源码

def process_image(img, scale, isotropic, crop, mean):
    '''Crops, scales, and normalizes the given image.
    scale : The image wil be first scaled to this size.
            If isotropic is true, the smaller side is rescaled to this,
            preserving the aspect ratio.
    crop  : After scaling, a central crop of this size is taken.
    mean  : Subtracted from the image
    '''
    # Rescale
    if isotropic:
        img_shape = tf.to_float(tf.shape(img)[:2])
        min_length = tf.minimum(img_shape[0], img_shape[1])
        new_shape = tf.to_int32((scale / min_length) * img_shape)
    else:
        new_shape = tf.pack([scale, scale])
    img = tf.image.resize_images(img, new_shape[0], new_shape[1])
    # Center crop
    # Use the slice workaround until crop_to_bounding_box supports deferred tensor shapes
    # See: https://github.com/tensorflow/tensorflow/issues/521
    offset = (new_shape - crop) / 2
    img = tf.slice(img, begin=tf.pack([offset[0], offset[1], 0]), size=tf.pack([crop, crop, -1]))
    # Mean subtraction
    return tf.to_float(img) - mean