# overlayPlot

Overlay two images.

## Syntax

    overlayPlot(bg, fg)
    overlayPlot(bg, fg, fg_dnr)
    overlayPlot(x, y, bg, fg, fg_dnr)

## Description

`overlayPlot` overlays two 2D images. The background image is displayed using a grayscale map. For a non-zero dynamic range, the foreground image is log compressed (discarding negative values), thresholded to a particular dynamic range, and overlaid using an alpha value of 0.5. If the dynamic range is set to zero, the foreground image is overlaid without additional processing.

Example:

    bg = rand(128);
    fg = peaks(128);
    overlayPlot(bg, fg);

## Inputs

`x, y` | vectors describing the position of the pixels in the image equivalent to `image`(x, y, c)
`bg` | background image
`fg` | foreground image

## Optional Inputs

Optional 'string', value pairs that may be used to modify the default computational settings.

Input | Valid Settings | Default | Description
--- | --- | --- | ---
`'ColorBar'` | (Boolean scalar) | `false` | Boolean controlling whether a colorbar is displayed.
`'ColorBarTitle'` | (string) | `'dB'` with log compression `''` otherwise | String defining the title used for the colorbar.
`'ColorMap'` | (string) | `'jet'` | String defining the colormap used for the overlay.
`'LogComp'` | (Boolean scalar) | `true` | Boolean controlling whether the forergound image is log compressed before display.
`'LogCompRef'` | (numeric scalar) | `max(fg(:))` | Reference value used in the log compression, where `fg_compressed = 20 * log10(fg ./ fg_ref)`.
`'NumColors'` | (integer scalar) | 256 | Number of colors used in the colormaps.
`'PowerTwo'` | (numeric two element vector) | `[-30, 0]` with log compression `[min(fg(:)), max(fg(:))]` otherwise | Plot scale used to display the foreground image.

## See Also

`beamPlot`, `voxelPlot`