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## density.read() -- read an EM (electron microscopy) density map file

`read(file, em_map_size, voxel_size, resolution, em_density_format='XPLOR', filter_type='NONE', filter_values=(0.0, 0.0), density_type='SPHERE', px=0, py=0, pz=0, cc_func_type='CCF')`

> This command reads a density map from file, which should be provided as a cubic grid of intensities, in the X-PLOR ([Brünger, 1992]) or MRC format. The size of the cubic grid is given by em_map_size. The density map resolution and the map voxel size are given by resolution and voxel_size, respectively.

> When fitting the probe into the EM grid, the probe structure is converted first into probe density, by using the function indicated in the density_type variable. Each atom can be represented by one of several atomic density functions, including, the uniform sphere model (`'SPHERE'`), the Gaussian function (`'GAUSS'`), a normalized Gaussian function (`'NORM'`), a hybrid Gaussian/sphere model (`'HYBRID'`), and an interpolation to the closest point on the grid (`'TRACE'`). The recommended function is `'SPHERE'`.

> When calculating the cross-correlation coefficient between a probe model and the density map, ccf_func_type specifies if you want the normalized cross-correlation coefficient (`'CCF'`), or the local cross-correlation coefficient (`'LCCF'`).

Example: See density.grid_search() command.

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