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= [wiki:Tutorial] / Projection objects =
Projection objects are used in various ways for image or field analysis, as shown in the following examples. Let us choose now a color image as input, UVMAT_DEMO02_color/images/frame1.jpg' (the folder 'UVMAT_DEMO02_color' is accessible on http://servforge.legi.grenoble-inp.fr/pub/soft-uvmat/).

== Plotting a luminosity profile ==
Create a line by the menu bar command '''Projection object/line'''. A new GUI '''set_object''' appears on the right side, with default settings '''Type'''='line', '''!ProjMode'''='projection'. Draw a line with the mouse, left hande side button to mark the beginning and end of the line. The luminosity profile, with the three rgb image components, appears in a new GUI '''view_field'''. The following figure shows the main GUI '''uvmat''', the GUI '''set_object''' which sets the object parameters, and the GUI '''view_field''' where the projected field is plotted:

[[Image(set_object.jpg)]]

These two GUIs can be made visible or not by selecting '''[!CheckViewObject'''] or '''[!CheckViewField]''' respectively in the frame '''Objects''' of '''uvmat'''.

Once created, the line can be moved with the mouse, or by directly introducing the coordinates of the line in the table '''[Coord]''' of the GUI '''set_object'''. A line aligned with the x or y axis can be directly created by the menu bar command '''Projection object/line_x''' or '''Projection object/line_y''' respectively.

== Getting the image histogram in a sub-region ==
This is obtained by creating a contour object, a polygon, a rectangle or an ellipse, using '''Projection object/polygon''', '''Projection object/rectangle''' or '''Projection object/ellipse'''. Draw the contour with the mouse to plot the histogram of the image inside the contour.  To get the histogram of the region outside the contour, select thecheck box  '''[edit'''] in the frame '''Objects''' of '''uvmat'''. Then in the GUI '''set_object''', select 'outside' in the menu '''[!ProjMode'''] and press the button '''[REFRESH'''].

== Resampling the image ==
The image can be resampled by linear interpolation of image luminosity on a grid, by selecting '''Projection object/plane'''. Then on the GUI '''set_object''', select 'interp_lin' in the menu '''[!ProjMode]'''. Set the mesh in x and y by the edit boxes '''[num_DX]''' and ['''num_DY'''], for instance with values 10, and press '''REFRESH'''. The image interpolated on this coarse grid is then displayed. It is also possible to reduce the range of x and y by the edit boxes ['''num_RangeX_1'''] and '''_2''' and '''[num_RangeY_1]''' and '''_2'''. Finally it is also possible to rotate the projection grid by setting the angle (in degrees) in the edit box '''[num_Angle_3'''].