Image Processing. Segmentation Process of partitioning a digital image into multiple segments (sets of pixels). 2. Clustering pixels into salient image regions, i.e., regions corresponding to individual surfaces, objects, or natural parts of objects. Image Processing. Segmentation
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Image Processing
Segmentation
Process of partitioning a digital image into multiple segments (sets of pixels).
2. Clustering pixels into salient image regions, i.e., regions corresponding to individual surfaces, objects, or natural parts of objects.
Image Processing
Segmentation
Used to locate objects and boundaries (lines, curves, etc.) in images.
Process of assigning a label to every pixel in an image such that pixels with the same label share certain visual characteristics.
Image Processing
Segmentation
Two of the most common techniques:
thresholding
and
edgefinding
Image Processing
Segmentation
Two of the most common techniques:
edgefinding
thresholding
Image Processing
The original image:
The objects in image:
A parameter called the brightnessthreshold is chosen and applied to the image f(x, y) as follows:
(x, y) Object f(x, y)
or
(x, y) Object f(x, y)
A. Threshold
Image Processing
The original image:
The objects in image:
Remark:
The output is the label "object" or "background" which, due to its dichotomous nature, can be represented as a Boolean variable "1" or "0".
A. Threshold
Image Processing
The original image:
The objects in image:
How to choose the threshold ?
A. Threshold
Image Processing
A threshold will be chosen independently of the image data
Fixed threshold
Image Processing
Fixed threshold
Source and segmented images with fixed threshold 128
Ảnh I:
Ảnh I đã được phân đoạn với ngưỡng 200 cho thành phần RED:
R = 200
Image Processing
Ảnh I:
Ảnh I đã được phân đoạn với ngưỡng 170:
R = 170
Image Processing
Isodata algorithm
Isodata algorithm
The threshold chosen by Isodata algorithm is 139
Ảnh I:
Isodata algorithm
Ảnh I đã được phân đoạn với ngưỡng 134:
= 134,
k=2
Ảnh I:
Isodata algorithm
Ảnh I đã được phân đoạn với ngưỡng 128:
k=1
Ảnh I:
Isodata algorithm
Ảnh I đã được phân đoạn với ngưỡng 116:
= 116, k=4
m1 = 0; m2 = L;
teta = (m1 + m2) / 2
stop = false
while !stop
ts1 = 0; ts2 = 0
ms1 = 0; ms2 = 0
for i = 0 to teta
ts1 = ts1 + h(i) * i
ms1 = ms1 + h(i)
m1 = ts1/ms1
for i = teta to L
ts2 = ts2 + h(i) * i
ms2 = ms2 + h(i)
m2 = ts2/ms2
tg = Round((m1 + m2) / 2)
if teta - tg <
stop = true
teta = tg
loop
Isodata algorithm
= 116, k=4
Image Processing
Triangle algorithm
A line is constructed between the maximum of the histogram at brightness bmax and the lowest value bmin = (p=0)% in the image.
Image Processing
Triangle algorithm
The distance d between the line and the histogram h[b] is computed for all values of b from b = bmin to b = bmax.
Image Processing
Triangle algorithm
The brightness value bo where the distance between h[bo] and the line is maximal is the threshold value, that is, = bo.
Image Processing
Triangle algorithm
Source and segmented images with threshold 152 chosen by triangle algorithm
dominant peak (183)
Image Processing
Background-symmetry algorithm
Assumes a distinct and dominant peak for the background that is symmetric about its maximum.
Image Processing
Background-symmetry algorithm
Image Processing
Background-symmetry algorithm
the object pixels are located to the left of the background
peak at brightness 183, that mean
h(183) = max {h(a): 0 h(a) 255 } = 351
search on the right of that peak to locate to find 95%. The total number of pixels in the image is 17424 and the total number of pixels on the right of peak is 8241, about 95% (94.59%) of 17424/2 = 8712.
Image Processing
Background-symmetry algorithm
At which brightness value 5% of the pixels lie to the right (are above)? This occurs at brightness 216. The number of pixels on the right of 216 is 936, equal to 5% (0.0537) the total number of pixels in the image: 17424.
Because of the assumed symmetry, we use as a threshold a displacement to the left of the maximum that is equal to the displacement to the right where the p% is found.
Image Processing
Background-symmetry algorithm
This means a threshold value given by
= 183 - (216 - 183) = 150.
In formula:
Image Processing
Background-symmetry algorithm
Source and segmented images with fixed threshold 150
Một vài ứng dụng
Bài toán:
Input: Ảnh I
Output: Ảnh I có chứa đám lửa?
Một vài ứng dụng
=170 (b)
Một vài ứng dụng
Đặc trưng màu điểm ảnh thuộc phần 1 (đám lửa)(1):
(1) Đào Thanh Tĩnh, Hà Đại Dương, Một mô hình phát hiện đám cháy qua ảnh video, Tạp chí Khoa học và Kỹ thuật, ISSN-1859-0209, tr. 5-11, Số 127, 4-2009.
Ảnh I:
Một vài ứng dụng
Ảnh I đã được phân đoạn với ngưỡng 200 cho thành phần RED: