当然 tensorflow 并不是一种用于图像处理的框架，这里图像处理仅仅是一些简单的像素级操作，最终目的比如用于数据增强；
- tf.random_crop()
- tf.image.random_flip_left_right()：
- tf.image.random_hue()
- random_contrast()
- random_brightness()
- random_saturation()
def pre_process_image(image, training):
# This function takes a single image as input,
# and a boolean whether to build the training or testing graph.
if training:
# For training, add the following to the TensorFlow graph.
# Randomly crop the input image.
image = tf.random_crop(image, size=[img_size_cropped, img_size_cropped, num_channels])
# Randomly flip the image horizontally.
image = tf.image.random_flip_left_right(image)
# Randomly adjust hue, contrast and saturation.
image = tf.image.random_hue(image, max_delta=0.05)
image = tf.image.random_contrast(image, lower=0.3, upper=1.0)
image = tf.image.random_brightness(image, max_delta=0.2)
image = tf.image.random_saturation(image, lower=0.0, upper=2.0)
# Some of these functions may overflow and result in pixel
# values beyond the [0, 1] range. It is unclear from the
# documentation of TensorFlow 0.10.0rc0 whether this is
# intended. A simple solution is to limit the range.
# Limit the image pixels between [0, 1] in case of overflow.
image = tf.minimum(image, 1.0)
image = tf.maximum(image, 0.0)
else:
# For training, add the following to the TensorFlow graph.
# Crop the input image around the centre so it is the same
# size as images that are randomly cropped during training.
image = tf.image.resize_image_with_crop_or_pad(image,
target_height=img_size_cropped,
target_width=img_size_cropped)
return image