Sketch recognition using transfer learning

Humans have an excellent ability to recognize freehand sketch drawings despite their abstract and sparse structures. Understanding freehand sketches with automated methods is a challenging task due to the diversity and abstract structures of these sketches. In this paper, we propose an efficient freehand sketch recognition scheme, which is based on the feature-level fusion of Convolutional Neural Networks (CNNs) in the transfer learning context. Specifically, we analyse different layer performances of distinct ImageNet pretrained CNNs and combine best performing layer features within the CNN-SVM pipeline for recognition. We also employ Principal Component Analysis (PCA) to reduce the fused deep feature dimensions to ensure the efficiency of the recognition application on the limited-capacity devices. We perform evaluations on two real sketch benchmark datasets, namely the Sketchy and the TU-Berlin to show the effectiveness of the proposed scheme. Our experimental results show that, the feature-level fusion scheme with the PCA achieves a recognition accuracy of 97.91% and 72.5% on the Sketchy and TU-Berlin datasets, respectively. This result is promising when compared with the human recognition accuracy of 73.1% on the TU-Berlin dataset. We also develop a sketch recognition application for smart devices to demonstrate the proposed scheme.