python - android上图像预处理方法的实现

Question

您能否建议一个库（或片段）在 Android API 18 上实现预处理 Python 方法（例如numpy.expand_dims()或img_to_array）（以部署基于 TensorFlow Mobile 的应用程序）？Java 上有与 Python 类似的库（例如 ND4J），但它们需要运行 API 级别 21 或更高级别的设备或模拟器。

from keras.preprocessing.image import img_to_array
import numpy as np

    image = img_to_array(image)
    image = np.expand_dims(image, axis=0)
    image /= 255.

Answer 1

我是一个交互式会话：

In [168]: np.source(np.expand_dims)
In file: /usr/local/lib/python3.5/dist-packages/numpy/lib/shape_base.py

def expand_dims(a, axis):
    """
    .... docs
    """
    a = asarray(a)
    shape = a.shape
    if axis > a.ndim or axis < -a.ndim - 1:
        # 2017-05-17, 1.13.0
        warnings.warn("Both axis > a.ndim and axis < -a.ndim - 1 are "
                      "deprecated and will raise an AxisError in the future.",
                      DeprecationWarning, stacklevel=2)
    # When the deprecation period expires, delete this if block,
    if axis < 0:
        axis = axis + a.ndim + 1
    # and uncomment the following line.
    # axis = normalize_axis_index(axis, a.ndim + 1)
    return a.reshape(shape[:axis] + (1,) + shape[axis:])

所以基本上它使用reshape, 形状在正确的位置包含大小1尺寸。这也可以用[:,:,np.newaxis,...]语法来完成。

其中任何一个是否可移植到 Java 取决于该语言中的数组实现。