====== Spectra ======
Spectra plots the spectrum of an image, the value of each band, in a separate window.

^ Argument ^ What it does ^ Default ^
| roi | Analyze only these regions. Enter several windows, 4 numbers each, one after another; each region is plotted separately, in its own color | the whole image |
| operation | For each band, the **average** or the **maximum** of the values inside each window | average |

The plot window can be resized. Turn the scroll wheel to magnify the plot, and drag it with the left mouse button. Hold down **Shift** to show the x and y values at the cursor.

Spectra passes the image on unchanged to any module connected after it. For a quick spectrum of a region, you can also right-click a window in Show and choose **Spectrum**; see [[basic_level:show:display_window|Show – The Display Window]].