(September 30, 2017)
Auto Seamer is a tool that assists in the creation of tileable textures. To use it, export your texture to BMP and import it into the program.
Auto Seamer contains three tools that can be set to operate horizontally, vertically, or both. The weighted seam tool will sample pixels (the Divisor setting sets the amount) along the edges of the texture and mirror them across multiple passes. The offset seam tool will brighten the edges, and the speckle tool will fuzz the edges. You can also set how far from the seam to average the color values under the effect of the tools.