# Montage Viewer: Introduction

The Montage Viewer, mViewer, is a command line application or visualizing FITS images, overlaying content (grids, symbols., ... ) on them and creating PNG or JPEG files. It can be included in scripts or pipelines. The image of M51 on the left was created with mViewer, with no manual retouching of the image.

mViewer has broad applicability for visualizing astronomical data. The following is a list of of its most useful capabilities:

Click image to view larger version in a new tab. | A range of data stretching algorithms, including a couple of custom stretches based on the idea of histogram matching to a general model of astronomical brightness distributions (log-trasformed gaussian histogram equalization). Gray/pseudo-color display of a single plane image with a number of color tables. Full-color (three image) display with optional color enhancement. Coordinate grid overlays (any coordinate system, including Besselian/Julian and Equinox selection). Astronomical catalog overlays with data in any coordinate system. Multiple symbols and any color. Includes optional scaling of the symbols by flux / magnitude based on any table column. Image metadata (outlines) overlays. Uses four corner data if the table contains this. Otherwise trys to interpret tables columns as WCS information. Custom ad hoc markers and labels. Output as JPEG or PNG, including embedded AVM tags in JPEGs (e.g., for export to WWT or for outreach uses).

The low-level mViewer functionality is a stand-alone program suitable for inclusion in scripts or as part of a pipeline. It can also be folded together with Python wrapping code (and a couple of other Montage modules) to support off-line interactive science visualization of astronomical images or with Javascript and CGI wrappers as an interactive web service suitable for sites wanting to allow interaction with their image holdings.