Moving outwards in concentric bands, the colors get fewer and fewer until there's a band with only one color, often black. Then still further outwards, there are more and more colors again. This one has a horizontal axis, but no vertical one. Then in the center there's a node that suggests to me the center of a galaxy. Still another image using the canvas texture.
Sine waves move from left to right, and their meetings at the equator create the image.
This particular image is my favorite out of a large series that I collectively think of as rugs or plaids. This one and many others features a screen 625 pixels wide and 343 pixels high. This allows four loops of five for the horizontal variables, for five to the fourth power is 625. Vertically, we have three loops of seven, for seven cubed is 343. Once the 7 loops are in place, the 7 index variables can be va- riously added, multiplied, anded, xored, etc., etc., to create the color.