Table 4 Brief information of several expression datasets.

From: Pet dog facial expression recognition based on convolutional neural network and improved whale optimization algorithm

Name

Categories of expression

Number of images

Resolution

JAFFE

Happiness, sadness, surprise, anger, fear, disgust, neutral

213

256 × 256

CK+

Neutral, sad, surprise, happiness, fear, anger, contempt, disgust

593

640 × 490

Oulu-CASIA

Surprise, happiness, sadness, anger, fear, disgust

2880

320 × 240