Prediction for one image in keras

Part 1 (2017)
1

I have trained and tested my model - now I want to use it to predict for a given path to an image file - how can I do this?

2

You can use model.predict method for doing . Will be able to help if you can provide more information

3

In Keras Documentation https://keras.io/models/sequential/

predict

function is used for predicting the images in the test set.

predict(self, x, batch_size=32, verbose=0)

In general,

from keras.models import Sequential
model_cnn = your_model() # python function for your cnn model
’’‘
Compile your model.
Fit your model.
Train your model.
’’'
model_cnn.predict(test_set, batch_size = your_size, verbose = 0)

4

I have the same question as the OP.

Here is what I’ve done.

import cv2
img = cv2.imread(path_to_one_file)
print(vgg.model.predict([img])) # model is already trained

This gives
ValueError: Error when checking : expected lambda_input_2 to have 4 dimensions, but got array with shape (499, 381, 3)

I then tried to resize doing:

import cv2
img = cv2.imread(path_to_one_file)
img = np.array([img]).reshape((1, 3, 224, 224))
print(vgg.model.predict([img])) # model is already trained

After that I get:
ValueError: cannot reshape array of size 570357 into shape (1,3,224,224)

There must be some preprocessing step that I’m missing. Any ideas?

5

Did resized the test images before using them to predict ?

Note :- Your train, test images needed to be of same size.

6

I tried some more resizing, but i’m not quite there yet. Below is what I’ve done.

import cv2
img = cv2.imread(path_to_one_file)
img = cv2.resize(img, (244, 244)) # img has shape (244, 244, 3), we need (3, 244, 244)
print(vgg.model.predict(np.array(img).reshape((1, 3, 244, 244)))) # This is were I'm confused

This gives the error:

ValueError: Error when checking : expected lambda_input_1 to have shape (None, 3, 224, 224) but got array with shape (1, 3, 244, 244)

Ideas?

7

In last line you are using a 4D tensor instead of a 3D tensor. You are training your model with shape (img_width, img_height, num_channels) That’s correct till line 3. When using the data for prediction you have to use the same dimensions of image. Instead of 3D tensor you are using a 4D
reshape((1, 3, 244, 244)) . If you look at the ValueError you will see that [quote=“chasesc, post:6, topic:4696”]
expected lambda_input_1 to have shape (None, 3, 224, 224)
[/quote]

which expresses a tensor of shape (batch_size, img_width, img_height, num_channels).
Now in line 2 you did not used a batch_size as a dimension but during prediction you are using it as 1.