Artifact-Free Image Style Transfer by Using Feature Map Clamping

Style transfer is an application that applies colors and patterns of a style image to a content image. In the previous style transfer method, a decoder was trained by using only positive valued feature maps from the last rectified linear unit (ReLU) layer of an encoder network. Then, the trained decoder was used to generate a stylized image from a transformed feature map, which may have unseen negative values due to the transformer operation, and this resulted in odd colors and patterns on the output stylized image. In this paper, we propose a simple but effective technique, called the feature map clamping method, which eliminates negative values from a transformed feature map to resolve style degradation in output stylized image. Our experiments that compare the output style qualities of the previous and our methods verified that our method removed odd colors and patterns appearing in the previous method and that our method had 12.07 % lower averaged feature loss and 7.22 % higher averaged user preference than the previous method without losing computational efficiency.