User`s guide

Key Blockset Con cepts
positions. Seco nd, the spatial coordinates of the cente r point of any p ix el are
identical to the pixel coordinates for that pixel. However, the pixel coordinate
system is discrete, while the spatial coordinate system is continuous. T his
means that, in pixel coordinates, the upper-left corner of an image is (0,0),
while in spatial coordinates, this location is (-0.5,-0.5). The spatial coordinate
system used by Video and Imag e Processing Blockset differs from the one
used by Image Processing Toolbox. For more informatio n on this spatial
coordinate system, see “Spatial Coordinates” in the Image Pro cessing Toolbox
documentation.
Image Data Stored in Column-Major Format
MATLABandVideoandImageProcessing Blockset use a column-major
numbering scheme to represent data elements internally. That means that
they internally store data elements from the first column first, then data
elements from the second column s econ d, and so on through the last column.
If you have imported an image or a v ideo stream into the MATLAB workspace
using a function from MATLAB or Image Processing Toolbox, the Video and
Image Processin g Blockset b locks will display this image or video stream
correctly. If you have written your own function or code to import images into
MATLAB, you must take the column-major convention into account.
Sample Time
Because the Video and Image Processing blocks calculate values directly
rather than solving differential equations, you m ust configure the Simulink
Solver to behave like a s che duler. The following steps show yo u how to do this:
1 From the m odel’s Simulation menu, select Configuration Parameters.
The Configuration dialog box opens.
2 From the Type list, choose Fixed-step.
3 From th e Solver list, choose discr ete (no cont inu ous states).
The following figure shows the correctly configured Configuration dialog
box.
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