Created
July 12, 2019 06:56
-
-
Save vashineyu/7fa66934b5f252629709dcc08b0e38f1 to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
# CAM | |
import cv2 | |
from PIL import Image | |
import tensorflow as tf | |
from tensorflow.python.keras import backend as K | |
def grad_cam_keras(model, im, class_select, layer, image_size, preproc_fn, alpha=0.6, filter_threshold=0.5): | |
"""GradCAM method for visualizing input saliency. | |
Args: | |
model: keras model | |
im: single image (with only RGB, [H,W,C]) | |
class_select: class to show | |
layer: layer name | |
image_size: tuple of image H,W | |
preproc_fn: preprocessing function | |
alpha: alpha | |
Returns: | |
gradient-class-activation-map | |
""" | |
H, W = image_size[0], image_size[1] | |
image = im.copy() | |
if len(image) != 4: | |
image = image[np.newaxis, :,:,:] | |
image_original = image[0].astype("uint8") | |
image = preproc_fn(image.astype("float32")) | |
if class_select is None: | |
output = model.predict(image) | |
y_c = model.output[0, output.argmax()] | |
print("Class-selected by prediction: {}".format(output.argmax())) | |
else: | |
y_c = model.output[0, class_select] | |
conv_output = model.get_layer(layer).output | |
grads = K.gradients(y_c, conv_output)[0] | |
gradient_function = K.function([model.input], | |
[conv_output, grads]) | |
with tf.device("/gpu:0"): | |
output, grads_val = gradient_function([image]) | |
output, grads_val = output[0, :], grads_val[0, :, :, :] | |
weights = np.mean(grads_val, axis=(0, 1)) | |
cam = np.dot(output, weights) | |
# Process CAM | |
cam = cv2.resize(cam, (H, W), cv2.INTER_LINEAR) | |
cam = np.maximum(cam, 0) | |
cam = cam / cam.max() | |
# Filter | |
cam[cam<filter_threshold] = 0 | |
# apply colormap | |
mapping = cv2.applyColorMap(np.uint8(255 * (1-cam)), cv2.COLORMAP_JET) | |
mapping = np.concatenate((mapping, ((mapping.max(axis=-1) - 128 )*255*alpha)[:,:,np.newaxis]), axis = -1) | |
background = Image.fromarray(image_original) | |
foreground = Image.fromarray(mapping.astype('uint8')) | |
background.paste(foreground, (0, 0), foreground) | |
return cam, background | |
## Usage | |
cam_map, raw_img = grad_cam_keras(model=model, | |
im=x_array[idx], ## raw image array (H,W,3) | |
class_select=None, | |
layer="conv5_block3_out", #"post_relu", | |
image_size=tuple(model.input.shape.as_list()[1:3]), # (H,W) | |
preproc_fn=preproc_fn) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment