Grayscale to Rainbow

1. Starting with #000000, create a grayscale gradient to #FFFFFF.

2. Create a gradient from #010000 to #FFFEFE with the correct length to encompass all red values between. Go through each of the 5 other hues possible for the same gradient length.

3. Continue the process, creating a new gradient starting with an increased starting red value and ending with a decreasing green and blue value. Create the rest of the other gradients of the same length at increasing hue values.

4. Repeat step 3 until the starting red value has reached 255, the ending green and blue values have reached 0, and the final hue has been reached.

The image is drawn left to right - row by row - top to bottom.

Image Licence: Public Domain (CC0).