====== Pattern ======
Pattern generates a test image of a given size. It has no input. Patterns include random values, a constant gray level or color, and a wedge.

^ Argument ^ What it does ^
| size | Required. The "width" and "height" of the output, in pixels. One number gives a square image |
| dataType | Required. **unsignedInteger**, **signedInteger** or **floating** |
| bits | 8 (the default) or 16 for integers; 32 or 64 for floating point |
| level | A constant gray level. The output has 1 band |
| bands | With "level": the number of bands, each with the "level" value |
| color | Three values, red, green and blue. The output is a 3-band color image |
| wedge | Four values for the corners: upper left, upper right, lower left, lower right |