What are the properties in a BoundingBox from regionprops?

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Recap
Recap 2016-3-27
评论： cpaniaguam 2023-11-9
I'm trying to figure out what coordinates are being stored from a BoundingBox. For instance
L=logical(bw);
box=regionprops(L,'Area', 'BoundingBox');
box(2)
And the output
ans =
Area: 127
BoundingBox: [10.5000 11.5000 10 19]
What are those 4 values? Is it the [top left, top right, bottom left, bottom right] coordinates?
  2 个评论
abdelrahim hashem
abdelrahim hashem 2019-1-14
Please Sir, why the values of the two components x and y is real values? Also, the last two values width and heigh are integer values?
Walter Roberson
Walter Roberson 2019-1-14
There is the question of whether coordinates represent pixel centers or pixel edges.

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采纳的回答

Image Analyst
Image Analyst 2016-3-27
It's [left, top, width, height]. Just be aware that the left and top are 0.5 pixels to the left and above, respectively, than the actual first column and first row of the binary image. It's because the Bounding box is defined such that it "contains" the blob, and if it ran right through the center of the top-most and left-most pixel, then that definition becomes somewhat ambiguous.
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Image Analyst
Image Analyst 2023-11-8
Ran in:
@cpaniaguam the bounding box is [xLeft, yTop, width, height], and xLeft and yTop are half a pixel outside of the left most and uppermost white pixel. xLeft and yTop always end in .5 since it's outisde the blob, not on the blob, and this is just the convention they use. So if you want the actual left column and top row of the blob, you must call ceil to round them up.
And the width and height are the width and height of the bounding box, which is larger than the actual blob by half a pixel all the way around. But the width and height are of the actual blob, not the bounding box of the blob. So if you want xRight and yBottom, you must add the width-1 and height -1 to the xLeft and yTop. See this example:
img = false(5,7);
img(2:4, 3:6) = true
img = 5×7 logical array
0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 1 1 1 1 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0
props = regionprops(img, 'BoundingBox');
boundingBox = props.BoundingBox
boundingBox = 1×4
2.5000 1.5000 4.0000 3.0000
xMin = ceil(boundingBox(1))
xMin = 3
xMax = xMin + boundingBox(3) - 1
xMax = 6
yMin = ceil(boundingBox(2))
yMin = 2
yMax = yMin + boundingBox(4) - 1
yMax = 4
I hope that explains it better.

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更多回答（2 个）

elvis okacha
elvis okacha 2019-4-12
编辑：Walter Roberson 2019-4-12
I am trying to find length and width.is this ok?:
I=Imread(filename)
Info=imfinfo(filename)
Thres=graythresh(I)
I2=~(im2bw(I,thresh))
cmp=bwconncomp(I2)
s=regionprops(cmp,'BoundingBox')
x=s.BoundingBox(3)
y=s.BoundingBox(4)
res=info.ResolutionUnit
resX=info.XResolutionUnit
resY=info.YResolutionUnit
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Walter Roberson
Walter Roberson 2019-4-12
Your image has multiple regions, so s is returning a nonscalar structure.
bb = vertcat(s.BoundingBox);
x = bb(:,1);
y = bb(:,2);
width = bb(:,3);
height = bb(:,4);
These will each be vectors, reflecting the fact that you have multiple regions.

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SOURABH BHATTACHARYA
编辑：SOURABH BHATTACHARYA 2022-1-22
The first two are the top left (x,y) coordinates while the later ones are for max width and height respectively along the respectives axes.

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