Version 19 (modified by vaillant1p, 9 years ago) (diff)


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

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:

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 the check 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].

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