model.py 文件源码

def generate_anchors(boxes, height, width, conv_height, conv_width):
    '''Generate anchors for given geometry

    boxes: K x 2 tensor for anchor geometries, K different sizes
    height: source image height
    width: source image width
    conv_height: convolution layer height
    conv_width: convolution layer width

    returns:
    conv_height x conv_width x K x 4 tensor with boxes for all
    positions. Last dimension 4 numbers are (y, x, h, w)
    '''
    k, _ = boxes.get_shape().as_list()

    height, width = tf.cast(height, tf.float32), tf.cast(width, tf.float32)

    grid = tf.transpose(tf.stack(tf.meshgrid(
        tf.linspace(-0.5, height - 0.5, conv_height),
        tf.linspace(-0.5, width - 0.5, conv_width)), axis=2), [1, 0, 2])

    # convert boxes from K x 2 to 1 x 1 x K x 2
    boxes = tf.expand_dims(tf.expand_dims(boxes, 0), 0)
    # convert grid from H' x W' x 2 to H' x W' x 1 x 2
    grid = tf.expand_dims(grid, 2)

    # combine them into single H' x W' x K x 4 tensor
    return tf.concat(
        3,
        [tf.tile(grid, [1, 1, k, 1]),
         tf.tile(boxes, [conv_height, conv_width, 1, 1])]
    )