Graphics operations

Draw graphical primitives into an image stored in an array. The functions draw_xxx perform a similar operation to the functions plot_xxx from the Spatial Math Toolbox. However the draw_xxx render the graphical primitive into the image pixel array, whereas the plot_xxx use Matplotlib to render the graphical primitive in a figure window.

machinevisiontoolbox.base.graphics.draw_box(image, l=None, r=None, t=None, b=None, w=None, h=None, lb=None, lt=None, rb=None, rt=None, wh=None, centre=None, ax=None, bbox=None, ltrb=None, color=None, thickness=1, antialias=False)

Draw a box in an image

Parameters:

• image (ndarray(H,W), ndarray(H,W,P)) – image to draw into, greyscale or color

• l (int, optional) – left side coordinate

• r (int, optional) – right side coordinate

• t (int, optional) – top side coordinate

• b (int, optional) – bottom side coordinate

• bbox (array_like(4), optional) – bounding box [xmin, xmax, ymin, ymax]

• ltrb (array_like(4), optional) – bounding box [xmin, ymin, xmax, ymax]

• lb (array_like(2), optional) – left-bottom corner [x,y]

• lt (array_like(2), optional) – left-top corner [x,y]

• rb (array_like(2), optional) – right-bottom corner (x,y)

• rt (array_like(2), optional) – right-top corner (x,y)

• wh (array_like(2), optional) – width and height

• centre (array_like(2), optional) – box centre (x,y)

• color (scalar or array_like) – color of line

• thickness (int, optional) – line thickness, -1 to fill, defaults to 1

• antialias (bool, optional) – use antialiasing, defaults to False

• ax – axes to draw into

Type:

Matplotlib axes

Returns:

passed image as modified

Return type:

ndarray(H,W), ndarray(H,W,P)

Draws a box into the specified image using OpenCV. The input image is modified.

The box can be specified in many ways, any combination of inputs is allowed so long as the box is fully specified:

• bounding box [xmin, xmax; ymin, ymax]

• left-top-right-bottom [xmin, ymin, xmax, ymax]

• left side

• right side

• top side

• bottom side

• centre and width+height

• left-bottom and right-top corners

• left-bottom corner and width+height

• right-top corner and width+height

• left-top corner and width+height

where left-bottom is (xmin, ymin), left-top is (xmax, ymax)

Example:

>>> from machinevisiontoolbox import draw_box, idisp
>>> import numpy as np
>>> img = np.zeros((1000, 1000), dtype='uint8')
>>> draw_box(img, ltrb=[100, 300, 700, 500], thickness=2, color=200)
>>> draw_box(img, ltrb=[100, 300, 700, 500], thickness=-1, color=50)
>>> idisp(img)

(Source code, png, hires.png, pdf)

Note

• For images y increases downwards so \(y_{top} < y_{bottom}\)

• if image is a 3-plane image then color should be a 3-vector or colorname string and the corresponding elements are used in each plane.

Seealso:

plot_box opencv.rectangle

machinevisiontoolbox.base.graphics.plot_labelbox(text, textcolor=None, labelcolor=None, **boxargs)

Plot a labelled box using matplotlib

Parameters:

• text (str) – text label

• textcolor (str, array_like(3), optional) – text color, defaults to None

• labelcolor (str, array_like(3), optional) – label background color

• boxargs – arguments passed to plot_box

Plot a box with a label above it. The position of the box is specified using the same arguments as for plot_box. The label font is specified using the same arguments as for plot_text. If labelcolor is specified it is used as the background color for the text label, otherwise the box color is used.

Example:

>>> from machinevisiontoolbox import plot_labelbox
>>> plot_labelbox('labelled box', bbox=[100, 150, 300, 350], color='r')

(Source code)

Note

The label is drawn at the top of the box assuming that axes are drawn with the y-axis downward (image convention).

Seealso:

plot_box, plot_text

machinevisiontoolbox.base.graphics.draw_labelbox(image, text, textcolor=None, labelcolor=None, font='simplex', fontsize=0.9, fontthickness=2, **boxargs)

Draw a labelled box in an image

Parameters:

• text (str) – text label

• textcolor (str, array_like(3), optional) – text color, defaults to black

• labelcolor (str, array_like(3), optional) – label background color

• font (str, optional) – OpenCV font, defaults to cv.FONT_HERSHEY_SIMPLEX

• fontsize (float, optional) – OpenCV font scale, defaults to 0.3

• fontthickness (int, optional) – font thickness in pixels, defaults to 2

• boxargs – arguments passed to draw_box

Raises:

TypeError – can’t draw color into a greyscale image

Returns:

passed image as modified

Return type:

ndarray(H,W), ndarray(H,W,P)

The position of the box is specified using the same arguments as for draw_box. The label font is specified using the same arguments as for draw_text. If labelcolor is specified it is used as the background color for the text label, otherwise the box color is used.

Example:

>>> from machinevisiontoolbox import draw_labelbox, idisp
>>> import numpy as np
>>> img = np.zeros((500, 500))
>>> draw_labelbox(img, 'labelled box', bbox=[100, 500, 300, 600],
        textcolor=0, labelcolor=100, color=200, thickness=2, fontsize=1)
>>> idisp(img)

(Source code, png, hires.png, pdf)

Note

• if image is a 3-plane image then color should be a 3-vector or colorname string and the corresponding elements are used in each plane.

Seealso:

draw_box, draw_text

machinevisiontoolbox.base.graphics.draw_text(image, pos, text=None, color=None, font='simplex', fontsize=0.3, fontthickness=2, antialias=False)

Draw text in image

Parameters:

• image (ndarray(H,W), ndarray(H,W,P)) – image to draw into, greyscale or color

• pos (array_like(2)) – position of text (u,v)

• text (str) – text

• color (scalar, array_like(3), str) – color of text

• font (str, optional) – font name, defaults to “simplex”

• fontsize (float, optional) – OpenCV font scale, defaults to 0.3

• fontthickness (int, optional) – font thickness in pixels, defaults to 2

• antialias (bool, optional) – use antialiasing, defaults to False

Returns:

passed image as modified

Return type:

ndarray(H,W), ndarray(H,W,P)

The position corresponds to the bottom-left corner of the text box as seen in the image. The font is specified by a string which selects a Hershey vector (stroke) font.

Font name	OpenCV font name
'simplex'	Hershey Roman simplex
'plain'	Hershey Roman plain
'duplex'	Hershey Roman duplex (double stroke)
'complex'	Hershey Roman complex
'triplex'	Hershey Romantriplex
'complex-small'	Hershey Roman complex (small)
'script-simplex'	Hershey script
'script-complex'	Hershey script complex
'italic'	Hershey italic

Example:

>>> from machinevisiontoolbox import draw_text, idisp
>>> import numpy as np
>>> img = np.zeros((1000, 1000), dtype='uint8')
>>> draw_text(img, (100, 150), 'hello world!', color=200, fontsize=2)
array([[0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       ...,
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0]], dtype=uint8)
>>> idisp(img)
<matplotlib.image.AxesImage object at 0x7fa24bc94280>

(Source code, png, hires.png, pdf)

Note

• if image is a 3-plane image then color should be a 3-vector or colorname string and the corresponding elements are used in each plane.

Seealso:

plot_text opencv.putText

machinevisiontoolbox.base.graphics.draw_point(image, pos, marker='+', text=None, color=None, font='simplex', fontsize=0.3, fontthickness=2)

Draw a marker in image

Parameters:

• image (ndarray(H,W), ndarray(H,W,P)) – image to draw into, greyscale or color

• pos (array_like(2), ndarray(2,n), list of 2-tuples) – position of marker

• marker (str, optional) – marker character, defaults to ‘+’

• text (str, optional) – text label, defaults to None

• color (str or array_like(3), optional) – text color, defaults to None

• font (str, optional) – OpenCV font, defaults to cv.FONT_HERSHEY_SIMPLEX

• fontsize (float, optional) – OpenCV font scale, defaults to 0.3

• fontthickness (int, optional) – font thickness in pixels, defaults to 2

Raises:

TypeError – can’t draw color into a greyscale image

Returns:

passed image as modified

Return type:

ndarray(H,W), ndarray(H,W,P)

The text label is placed to the right of the marker, and vertically centred. The color of the marker can be different to the color of the text, the marker color is specified by a single letter in the marker string, eg. ‘b+’.

Multiple points can be marked if pos is a \(2 \times n\) array or a list of coordinate pairs. In this case:

• if text is a string it is processed with text.format(i) where i is the point index (starting at zero). “{0}” within text will be substituted by the point index.

• if text is a list, its elements are used to label the points

The font is specified by a string which selects a Hershey vector (stroke) font.

Font name	OpenCV font name
'simplex'	Hershey Roman simplex
'plain'	Hershey Roman plain
'duplex'	Hershey Roman duplex (double stroke)
'complex'	Hershey Roman complex
'triplex'	Hershey Romantriplex
'complex-small'	Hershey Roman complex (small)
'script-simplex'	Hershey script
'script-complex'	Hershey script complex
'italic'	Hershey italic

Example:

>>> from machinevisiontoolbox import draw_point, idisp
>>> import numpy as np
>>> img = np.zeros((1000, 1000), dtype='uint8')
>>> draw_point(img, (100, 300), '*', fontsize=1, color=200)
>>> draw_point(img, (500, 300), '*', 'labelled point', fontsize=1, color=200)
>>> draw_point(img, np.random.randint(1000, size=(2,10)), '+', 'point {0}', 100, fontsize=0.8)
>>> idisp(img)

(Source code, png, hires.png, pdf)

Note

• if image is a 3-plane image then color should be a 3-vector or colorname string and the corresponding elements are used in each plane.

Seealso:

plot_point opencv.putText

machinevisiontoolbox.base.graphics.draw_line(image, start, end, color, thickness=1, antialias=False)

Draw line in image

Parameters:

• image (ndarray(H,W), ndarray(H,W,P)) – image to draw into, greyscale or color

• start (array_like(2) int) – start coordinate (u,v)

• end (array_like(2) int) – end coordinate (u,v)

• color (scalar, array_like(3)) – color of line

• thickness (int, optional) – width of line in pixels, defaults to 1

• antialias (bool, optional) – use antialiasing, defaults to False

Raises:

TypeError – can’t draw color into a greyscale image

Returns:

passed image as modified

Return type:

ndarray(H,W), ndarray(H,W,P)

Example:

>>> from machinevisiontoolbox import draw_line, idisp
>>> import numpy as np
>>> img = np.zeros((1000, 1000), dtype='uint8')
>>> draw_line(img, (100, 300), (700, 900), color=200, thickness=10)
array([[0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       ...,
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0]], dtype=uint8)
>>> idisp(img)
<matplotlib.image.AxesImage object at 0x7feef56ea250>

(Source code, png, hires.png, pdf)

Note

• if image is a 3-plane image then color should be a 3-vector or colorname string and the corresponding elements are used in each plane.

Seealso:

plot_line opencv.line

machinevisiontoolbox.base.graphics.draw_circle(image, centre, radius, color, thickness=1, antialias=False)

Draw line in image

Parameters:

• image (ndarray(H,W), ndarray(H,W,P)) – image to draw into, greyscale or color

• centre – centre coordinate

• radius – radius in pixels

• color (scalar, array_like(3)) – color of circle

• thickness (int, optional) – width of line in pixels, -1 to fill, defaults to 1

• antialias (bool, optional) – use antialiasing, defaults to False

Raises:

TypeError – can’t draw color into a greyscale image

Returns:

passed image as modified

Return type:

ndarray(H,W), ndarray(H,W,P)

Example:

>>> from machinevisiontoolbox import draw_circle, idisp
>>> import numpy as np
>>> img = np.zeros((1000, 1000), dtype='uint8')
>>> draw_circle(img, (400,600), 150, thickness=2, color=200)
>>> draw_circle(img, (400,600), 150, thickness=-1, color=50)
>>> idisp(img)

(Source code, png, hires.png, pdf)

Note

• if image is a 3-plane image then color should be a 3-vector or colorname string and the corresponding elements are used in each plane.

Seealso:

plot_circle opencv.circle