bboxOverlapRatio

Compute bounding box overlap ratio

Syntax

overlapRatio = bboxOverlapRatio(bboxA,bboxB)

overlapRatio = bboxOverlapRatio(bboxA,bboxB,ratioType)

Description

overlapRatio = bboxOverlapRatio(bboxA,bboxB) returns the overlap ratio between each pair of bounding boxes bboxA and bboxB. The function returns the overlapRatio value between 0 and 1, where 1 implies a perfect overlap.

overlapRatio = bboxOverlapRatio(bboxA,bboxB,ratioType) additionally lets you specify the method to use for computing the ratio. You must set the ratioType to either 'Union' or 'Min'.

Examples

Compute the Overlap Ratio Between Two Bounding Boxes

Define two bounding boxes in the format [x y width height].

bboxA = [150,80,100,100]; 
bboxB = bboxA + 50;

Display the bounding boxes on an image.

I = imread('peppers.png');
RGB = insertShape(I,'filled-rectangle',bboxA,'ShapeColor','green');
RGB = insertShape(RGB,'filled-rectangle',bboxB,'ShapeColor','yellow');
imshow(RGB)

Compute the overlap ratio between the two bounding boxes.

overlapRatio = bboxOverlapRatio(bboxA,bboxB)

overlapRatio = 
0.0833

Compute Overlap Ratio Between Each Pair of Bounding Boxes

Randomly generate two sets of bounding boxes.

bboxA = 10*rand(5,4); 
bboxB = 10*rand(10,4);

Ensure that the width and height of the boxes are positive.

bboxA(:,3:4) = bboxA(:,3:4) + 10;
bboxB(:,3:4) = bboxB(:,3:4) + 10;

Compute the overlap ratio between each pair.

overlapRatio = bboxOverlapRatio(bboxA,bboxB)

overlapRatio = 5×10

    0.2431    0.2329    0.3418    0.5117    0.7972    0.1567    0.1789    0.4339    0.0906    0.5766
    0.3420    0.1655    0.7375    0.5188    0.2786    0.3050    0.2969    0.4350    0.2477    0.2530
    0.4844    0.3290    0.3448    0.1500    0.1854    0.4976    0.5629    0.4430    0.5027    0.2685
    0.3681    0.0825    0.3499    0.0840    0.0658    0.5921    0.6498    0.1930    0.7433    0.0676
    0.3752    0.1114    0.3114    0.0696    0.0654    0.5408    0.6234    0.2046    0.7557    0.0717

Input Arguments

bboxA — Bounding box

M-by-4 matrix | M-by-5 matrix

Bounding boxes, specified as an M-by-4 or M-by-5 nonsparse numeric matrix. M is the number of bounding boxes. Each row of the matrix defines a bounding box as either an axis-aligned rectangle or a rotated rectangle. This table describes the format for each bounding box.

Bounding Box	Row	Description
Axis-aligned rectangle	[xmin, ymin, width, height]	This type of bounding box is defined in pixel coordinates as an M-by-4 matrix representing M bounding boxes
Rotated rectangle	[xcenter, ycenter, width, height, yaw]	This type of bounding box is defined in spatial coordinates as an M-by-5 matrix representing M bounding boxes. The xcenter and ycenter coordinates represent the center of the bounding box. The width and height elements represent the length of the box along the x and y axes, respectively. The yaw represents the rotation angle in degrees. The amount of rotation about the center of the bounding box is measured in the clockwise direction.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

bboxB — Bounding box

M-by-4 matrix | M-by-5 matrix

Bounding boxes, specified as an M-by-4 or M-by-5 nonsparse numeric matrix. M is the number of bounding boxes. Each row, M, of the matrix defines a bounding box as either an axis-aligned rectangle or a rotated rectangle. This table describes the format for each bounding box.

Bounding Box	Row	Description
Axis-aligned rectangle	[xmin, ymin, width, height]	This type of bounding box is defined in pixel coordinates as an M-by-4 matrix representing M bounding boxes
Rotated rectangle	[xcenter, ycenter, width, height, yaw]	This type of bounding box is defined in spatial coordinates as an M-by-5 matrix representing M bounding boxes. The xcenter and ycenter coordinates represent the center of the bounding box. The width and height elements represent the length of the box along the x and y axes, respectively. The yaw represents the rotation angle in degrees. The amount of rotation about the center of the bounding box is measured in the clockwise direction.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

ratioType — Ratio type

'Union' (default) | 'Min'

Ratio type, specified as the character vector 'Union' or 'Min'.

• Set the ratio type to 'Union' to compute the ratio as the area of intersection between bboxA and bboxB, divided by the area of the union of the two.

• Set the ratio type to 'Min' to compute the ratio as the area of intersection between bboxA and bboxB, divided by the minimum area of the two bounding boxes.

Data Types: char

Output Arguments

overlapRatio — Overlap ratio between two bounding boxes

M-by-N matrix

Overlap ratio between two bounding boxes, returned as an M-by-N matrix. Each (I, J) element in the output matrix corresponds to the overlap ratio between row I in bboxA and row J in bboxB. The function returns overlapRatio in the between 0 and 1, where 1 implies a perfect overlap. If either bboxA or bboxB is double, then the function returns overlapRatio as double. Otherwise, the function returns it as single.

The function computes the overlap ratio based on the ratio type. You can set ratioType to 'Union' or 'Min':

Data Types: single | double

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2014b