MATLAB VIDEO AND IMAGE PROCESSING BLOCKSET 3 Guide de l'utilisateur télécharger pdf (Page 28)

1 Gettin g Started

For pixel coordinates, the first comp onent r (the row) increases dow nward,

while the second component c (the column) increases to the right. Pixel

coordinates are integer values and range from 0 to the length of the row or

column. The pixel coordinates used in Video and Image Processing Blockset

are zero based, w hile the pixe l coordinates used by Image Processing Toolbox

and MATLAB are one based. For more information on the pixel coordinate

system used by Image Processing Toolbox, see “Pixel C oordinates” in the

Image Processing Toolbox documentation.

Spatial Coordinates

Spatial coordinates enable you to specify a location in an image with greater

granularity than pixel coordinates. For example, in the pixel coordinate

system, a pixel is treated as a discrete unit, uniquely identified by an integer

row and column pair, such as (3,4). In a spatial coordinate system, locations

in an image can be represented in terms of partial pixels, such as (3.3, 4.7).

The following figure illustrates the spatial coordinate system used for image s:

2.5

1.5

0.5

-0.5

This spatial coordinate system corresponds to the pix el coordinate system

in the follow ing ways. First, both are defined in te rms of row a nd column

1-20

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 ... 251 252

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MATLAB VIDEO AND IMAGE PROCESSING BLOCKSET 3 Guide de l'utilisateur Page 28