Mask Creation Errors
Unintentional DeepDream Effects:
Notice the weird artifact in the middle area of the image:
The cause of this artifact comes from the content image's associated mask image:
A closer look at what the cause is:
You can see there is tiny white dot on the mask, where I forgot to fill the spot with the appropriate color. This mistake was not noticeable on smaller -image_size values, but at just over 1000px it creates a very noticeable effect on the image. This effect is caused by the style image's mask not having the color white anywhere on it, resulting in an area on the content image were there is nothing to transfer to.
This error illustrates that a content mask must have all it's colors matched by the style mask(s) that you are using. Though a style mask does not need to match all the colors on a content mask.