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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''''. 

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.

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'''.


== 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 '''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'''.