The movie from the camcorder has been exported as an .avi file, using standard programmes. If the appropriate codec is available (see section 1.3), the movie can be opened by the 'uvmat' interface using the browser like for individual images. The first frame is displayed, as well as the total number of frames 'last' (here 1884). If you cannot read the avi movie on your computer, an error message appears on the Matlab prompt. Then open the .png images instead: a set of selected frames have been copied to this format. The frames can be scanned by manually setting the frame number, or using the RUN buttons '+d' and '-d', like for series of image files. For instance to look at successive images every 4 seconds, put an increment 100, and press '+d'.
The image is in true color, made of three components red (r), green (g), blue (b), ranging from 0 to 255. The histogram of each color is plotted with the respective color in the histogram window on the right. A profile of each of the three components along any line can be also obtained by pushing 'set_line', drawing the line, and pressing RUN '0'. To see only the green component as a black and white image, come back to the 'view_field' ACTION and select the check box 'usr' near inside the 'ACTION' menu. This yields a browser looking for a user defined matlab processing function. Choose 'green.m' in the directory 'UVMAT/IMA_TRANSFORM'. You can alternatively choose 'sum_color.m' to sum the three color components, or write any other processing function.
Analysis on image series can be obtained by selected by the menu 'ACTION'. For instance it can be visualized as a movie with the option 'movie'. Press RUN '0' after setting the first and last frame numbers, as well as the increment. The movie speed can be adjusted by the slider 'movie speed' on the right. To stop the movie before the end, press 'STOP'.
Selecting 'average' provides an image average over the selected series. For instance averaging the frames around #1001, from 981 to 1021, provides a 'photo' with long exposure time, as shown in Fig. 4. The result is automatically recorded as an image 'movie_aver.png'. The wakes behind the cylinder is clearly visible. To get this figure, set the 'visu_window' to 2, and introduce the calibration 3.1 in 'pxcmx' and 'pxcmy' (see next subsection).
