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# Draw Markers

Draw markers by embedding predefined shapes on output image

## Library

Text & Graphics

`visiontextngfix`

## Description

The Draw Markers block can draw multiple circles, x-marks, plus signs, stars, or squares on images by overwriting pixel values. Overwriting the pixel values embeds the shapes.

This block uses Bresenham's circle drawing algorithm to draw circles and Bresenham's line drawing algorithm to draw all other markers.

### Port Description

PortInput/OutputSupported Data TypesComplex Values Supported

Image

M-by-N matrix of intensity values or an M-by-N-by-P color values where P is the number of color planes

• Double-precision floating point

• Single-precision floating point

• Fixed point

• Boolean

• 8-, 16-, and 32-bit signed integer

• 8-, 16-, and 32-bit unsigned integer

No

R, G, B

Scalar, vector, or matrix that represents one plane of the input RGB video stream. Inputs to the R, G, and B ports must have the same dimensions and data type.

Same as Image port

No

Pts

M-by-2 matrix of [x y] coordinates,

`$\left[\begin{array}{cc}{x}_{1}& {y}_{1}\\ {x}_{2}& {y}_{2}\\ ⋮& ⋮\\ {x}_{M}& {y}_{M}\end{array}\right]$`

where M is the total number of markers and each [x y] pair defines the center of a marker.

• Double-precision floating point

• Single-precision floating point

• 8-, 16-, and 32-bit signed integer

• 8-, 16-, and 32-bit unsigned integer

If the input to the Image port is an integer, fixed point, or boolean data type, the input to the Pts port must also be an integer data type.

No

ROI

Four-element vector of integers [x y width height] that define a rectangular area in which to draw the markers. The first two elements represent the one-based [x y] coordinates of the upper-left corner of the area. The second two elements represent the width and height of the area.

• Double-precision floating point

• Single-precision floating point

• 8-, 16-, and 32-bit signed integer

• 8-, 16-, and 32-bit unsigned integer

No

Clr

P-element vector or M-by-P matrix where P is the number of color planes.

Same as Image port

No

Output

Scalar, vector, or matrix of pixel values that contain the marker(s)

Same as Image port

No

The output signal is the same size and data type as the inputs to the Image, R, G, and B ports.

## Parameters

Marker shape

Specify the type of marker(s) to draw. Your choices are `Circle`, `X-mark`, `Plus`, `Star`, or `Square`.

When you select `Circle`, `X-mark`, or `Star`, and you select the Use antialiasing check box, the block performs a smoothing algorithm. The algorithm is similar to the `poly2mask` function to determine which subpixels to draw.

Marker size

Enter a scalar value that represents the size of the marker, in pixels.

Enter a scalar value, M, that defines a (2M+1)-by-(2M+1) pixel square into which the marker fits. M must be greater than or equal to `1`.

Filled

Select this check box to fill the marker with an intensity value or a color. This parameter is visible if, for the Marker shape parameter, you choose `Circle` or `Square`.

When you select the Filled check box, the Fill color source, Fill color and Opacity factor (between 0 and 1) parameters appear in the dialog box.

Fill color source

Specify source for fill color value. You can select ```Specify via dialog``` or `Input port`. This parameter appears when you select the Filled check box. When you select `Input port`, the color input port clr appears on the block.

Fill color

If you select `Black`, the marker is black. If you select `White`, the marker is white. If you select `User-specified value`, the Color value(s) parameter appears in the dialog box. This parameter is visible if you select the Filled check box.

Border color source

Specify source for the border color value to either ```Specify via dialog``` or `Input port`. Border color options are visible when the fill shapes options are not selected. This parameter is visible if you select the Filled check box. When you select `Input port`, the color input port clr appears on the block.

Border color

Specify the appearance of the shape's border. If you select `Black`, the border is black. If you select `White`, the border is white. If you select `User-specified value`, the Color value(s) parameter appears in the dialog box. This parameter is visible if you clear the Fill shapes check box.

Color value(s)

Specify an intensity or color value for the marker's border or fill. This parameter appears when you set the Border color or Fill color parameters to `User-specified value`. Tunable.

The following table describes what to enter for the color value based on the block input and the number of shapes you are drawing.

Block InputColor Value(s) for Drawing One Marker or Multiple Markers with the Same ColorColor Value(s) for Drawing Multiple Markers with Unique Color
Intensity imageScalar intensity valueR-element vector where R is the number of markers
Color image P-element vector where P is the number of color planesP-by-R matrix where P is the number of color planes and R is the number of markers

For each value in the parameter, enter a number between the minimum and maximum values that can be represented by the data type of the input image. If you enter a value outside this range, the block produces an error message.

Opacity factor (between 0 and 1)

Specify the opacity of the shading inside the marker, where `0` indicates transparent and `1` indicates opaque. This parameter appears when you select the Filled check box. This parameter is tunable.

The following table describes what to enter for the Opacity factor(s) (between 0 and 1) parameter based on the block input and the number of markers you are drawing.

Opacity Factor value for Drawing One Marker or Multiple Markers with the Same ColorOopacity Factor value for Drawing Multiple Marker with Unique Color
Scalar intensity valueR-element vector where R is the number of markers
Draw markers in

Specify the area in which to draw the markers. When you select `Entire image`, you can draw markers in the entire image. When you select ```Specify region of interest via port```, the ROI port appears on the block. Enter a four-element vector, `[x y width height]`, where `[x y]` are the coordinates of the upper-left corner of the area.

Use antialiasing

Perform a smoothing algorithm on the marker. This parameter is visible if, for the Marker shape parameter, you select `Circle`, `X-mark`, or `Star`.

Image signal

Specify how to input and output a color video signal. When you select `One multidimensional signal`, the block accepts an M-by-N-by-P color video signal, where P is the number of color planes, at one port. When you select ```Separate color signals```, additional ports appear on the block. Each port accepts one M-by-N plane of an RGB video stream.

 Draw Shapes Computer Vision Toolbox™ software Insert Text Computer Vision Toolbox software