Lua API: tracker#

Description#

The tracker data structure is used to assist color tracking in the CMUcam3. It holds information about tracking being done, and parameters that can be set to control which color is tracked and other aspects of the color tracking. TODO: Add a good description of what hte bounding box is, and what the centroid is

Example#

Here’s a short example that shows how the tracker object is used to find a red area in the CMUcam3 picture frame, and then that box is printed to the CamScripter debugging area in Eclipse.

trkr = tracker_new(195, 0, 0, 255, 45, 45); -- track red
trkr:set_noise_filter(3);  -- 2 is the default

take_picture();
tracker_track_color(trkr);
print_color_tracker(trkr);  -- print color tracker info to the screen
print("num pixels tracked: " .. trkr:get_num_pixels()); -- print number of red pixels found in the picture
-- print_picture(); -- uncomment this line to print the picture itself to the screen as well (slower)

Creation#

See tracker_new

Methods#

get_centroid_x
get_centroid_y
get_density
get_num_pixels
get_x0
get_x1
get_y0
get_y1
set_lower_bound
set_noise_filter
set_upper_bound

get_centroid_x#

trkr:get_centroid_x()

Parameters:: none
Return Values:: Integer x-coordinate of the centroid

Get the x-coordinate of the centroid of the color being tracked, where (0, 0) is the upper left hand corner of the picture.

get_centroid_y#

trkr:get_centroid_y()

Parameters:: none
Return Values:: Integer y-coordinate of the centroid

Get the y-coordinate of the centroid of the color being tracked, where (0, 0) is the upper left hand corner of the picture.

get_density#

trkr:get_density()

Parameters:: none
Return Values:: Density of the color being tracked

Get the density of the color tracked within the picture buffer. Density is a measure of how dense the color being tracked is within the color tracker bounding box – the more pixels of the color being tracked in the box, the higher the density is.

get_num_pixels#

trkr:get_num_pixels()

Parameters:: none
Return Values:: Number of pixels in the picture buffer matching the color tracker color

Get the total number of pixels of the color being tracked (as determined by the RGB values passed to tracker_new) that were found in the CMUcam3 picture buffer.

get_x0#

trkr:get_x0()

Parameters:: none
Return Values:: The integer value of the x-coordinate of the upper left hand corner of the color tracking bounding box.

When tracker_track_color is called, it establishes a bounding box that describes the boundaries of the color being tracked within the picture. (x0, y0) is the location of the upper left hand corner of that box, and (x1, y1) is the location of the lower right hand corner of that box within the picture buffer, where (0, 0) is the upper left hand corner of the picture buffer. get_x0 returns the x-coordinate of the upper left hand corner of the color boundary box.

get_y0#

trkr:get_y0()

Parameters:: none
Return Values:: The integer value of the y-coordinate of the upper left hand corner of the color tracking bounding box.

When tracker_track_color is called, it establishes a bounding box that describes the boundaries of the color being tracked within the picture. (x0, y0) is the location of the upper left hand corner of that box, and (x1, y1) is the location of the lower right hand corner of that box within the picture buffer, where (0, 0) is the upper left hand corner of the picture buffer. get_y0 returns the x-coordinate of the upper left hand corner of the color boundary box.

get_x1#

trkr:get_y1()

Parameters:: none
Return Values:: The integer value of the x-coordinate of the lower right hand corner of the color tracking bounding box.

When tracker_track_color is called, it establishes a bounding box that describes the boundaries of the color being tracked within the picture. (x0, y0) is the location of the upper left hand corner of that box, and (x1, y1) is the location of the lower right hand corner of that box within the picture buffer, where (0, 0) is the upper left hand corner of the picture buffer. get_x1 returns the x-coordinate of the upper left hand corner of the color boundary box.

get_y1#

trkr:get_y1()

Parameters:: none
Return Values:: The integer value of the y-coordinate of the lower right hand corner of the color tracking bounding box.

When tracker_track_color is called, it establishes a bounding box that describes the boundaries of the color being tracked within the picture. (x0, y0) is the location of the upper left hand corner of that box, and (x1, y1) is the location of the lower right hand corner of that box within the picture buffer, where (0, 0) is the upper left hand corner of the picture buffer. get_y1 returns the x-coordinate of the upper left hand corner of the color boundary box.

set_lower_bound#

trkr:set_lower_bound(integer channel, integer bound)

Parameters:: channel The channel you’re setting a bound for. See the channel of interest constants in Lua API: Constants. bound The minimum value possible for the given channel. Must be between 0 and 255.
Return Values:: none

Set the lower bound for one channel in the color tracker. The lower bound is the minimum value a pixel can have in that channel in order to be tracked. For color tracking purposes, for any pixel to be considered trackable, that pixel must be between the lower and upper bound in each of its channels.

set_noise_filter#

trkr:set_noise_filter(integer filter)

Parameters:: filter The new noise filter value. Default is 2.
Return Values:: none

The noise filter value determines how many consecutive active pixels before a pixel are required before the pixel should be counted as being detected by color tracking. The value must be between 0 and 255.

set_upper_bound#

trkr:set_upper_bound(integer channel, integer bound)

Parameters:: channel The channel you’re setting a bound for. See the channel of interest constants in Lua API: Constants. bound The maximum value possible for the given channel. Must be between 0 and 255.
Return Values:: none

Set the upper bound for one channel in the color tracker. The upper bound is the maximum value a pixel can have in that channel in order to be tracked. For color tracking purposes, for any pixel to be considered trackable, that pixel must be between the lower and upper bound in each of its channels.