Blotches detection

HNUE JOURNAL OF SCIENCE  
Natural Sciences, 2020, Volume 65, Issue 4A, pp. 51-57  
BLOTCHES DETECTION  
Nguyen Thi Quynh Hoa  
Falcuty of Information Technology, Hanoi National University of Education  
Abstract. Blotch detection and removal is an important issue for archive film restoration  
and it can be extended in many other field of image processing. In this work, a new  
proposal including an automatic detection method and inpainting scheme is introduced.  
First, a technique for automatically detecting blotches based on local changes of pixels on  
consecutive frames is applied. Specifically, a two-stage Simplified Ranked Order  
Difference (SROD) detector is proposed to identify blotches on frames. Next, an improved  
inpainting was applied to restore the blotches so that it is undetectable by viewers. Our  
proposal is executed automatically without external parameters. The proposal has been  
tested on a serial of natural images with different sizes and resolutions. Experimental  
results show that the proposed solution has been successfully detected with fairly high  
accuracy and quite smooth restored blotches. Based on result analysis, the proposal has  
many potential and applications in the future. Index Terms-blotch detection, blotch  
removal, restoration, inpainting.  
Keywords: Terms-blotch detection, blotch removal, restoration, inpainting.  
1. Introduction  
Storage and processing of visual aids that do not affect their overall quality is still a  
challenging problem. Storage and handling of old movies is even more difficult due to the  
physicochemical properties of the film. Indeed, many physical factors can affect the overall  
quality of the old-time movie such as moisture and heat, one of the factors responsible for  
the fading of old movies. One of the common issues of interest and research is the restoration of  
old films damaged by various problems like grainy, fuzzy, faded and artifacts other structures.  
Until now, a considerable effort has been devoted to developing methods and systems of digital  
precision to restore old film. The stretch marks and scratches are some artifacts film is the  
most popular study [1-2].  
During long time ago, the old film was restored by one of the two most common  
techniques that technical manual or semi-automatic. However, the quality of the recovery  
depends on the skill of the user and the limitations of the tools and methods used. For all  
these reasons, the film industry is always searching and researching the advantages of digital  
solutions. Some techniques are proposed based on the model of film degradation phenomena [3].  
However, these models often ignore the cognitive aspect and therefore excludes the human  
observer, the final judge. Various methods for removing spots have been proposed in the  
literature. Some methods based on image printing techniques [4-5]. In addition, a simple way  
Received March 20, 2020. Revised May 7, 2020. Accepted May 14, 2020  
Contact Nguyen Thi Quynh Hoa, e-mail address: [email protected]  
51  
Nguyen Thi Quynh Hoa  
to expand the method to blur images into videos however it can lead to incoherent results [6]  
and especially around moving objects.  
The purpose of this work we propose a complete solution for detecting and removing spots  
movies based on some perceived feature of the human visual system. The performance of each  
component is assessed through objective research extensively tested on real video. The  
perceived quality of the frames has been restored and are evaluated by fuzzy picture quality  
printing for professional use.  
2. Content  
2.1. Monoresolution detection of suspicious regions  
k)  
An input image I( could be easily represented at different resolution levels by a Gaussian  
pyramid. The spots are treated like a change of lighting locally between the degraded image  
I( and every reference I(k-1) and I( . However, earlier methods are not handling the  
different size of the spot as well as the shift of different intensity, because it works directly  
on the resolution of the input image. This leads to reduce the incidence of false alarms and  
improve detection accuracy rate [7]. The spot detection includes the two main steps. First  
identify likely areas placed first broken. Then, a heuristic detection for SROD only machine is  
applied to those areas. More precisely, the suspicious region is positioned using a powerful  
movement patterns to lighting variations. In this respect, we retain the affine motion model  
proposed in [8] for efficiency and simplicity of it. Taking into consideration the displacement  
k)  
k+1)  
k-1,k  
dj(  
(rj) of the pixel rj between Aj(k-1) and Aj(k), and the illumination coefficient hj(k-1,k) that  
)
reflects its intensity change between both sub-images, the observation model is defined by  
ꢂ ꢄ  
ꢂ
ꢁ
ꢄ
ꢂ
ꢁ
ꢄ
ꢂ
ꢁ
ꢄ
ꢂ
ꢃ−ꢇ,ꢃ  
ꢀꢁꢃ (ꢅ ) ꢆ ℎ  
(ꢅ )ꢀ ꢃ−ꢇ ꢈꢅ ꢉ ꢊ  
(ꢅ )ꢋ ꢉ ꢌ  
ꢁ
ꢄ(ꢅ )  
(1)  
ꢃ−ꢇ,ꢃ  
ꢃ−ꢇ,ꢃ  
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢂ
ꢁ
ꢄ
ꢃ−ꢇ,ꢃ  
where ꢌ  
is the estimation error. As these parameters are locally valid, they are estimated  
in blockwise way by ther Block-Matching algorithm (BMA). Thus, the sub-image Aj(k) is firstly  
partitioned into blocks ꢍꢂꢃꢄ of size ℓꢁ × ℓꢁ ∈ꢑ[1, … , ] × [1, … , ]. Then, the optimal block  
ꢒ
ꢒ
ꢔ
ꢓ
ꢏ
ꢏ
ꢂꢎ ,ꢐ ꢄ  
ꢏ
ꢏ
2
2
ꢂꢃ−ꢇꢄ  
ꢍ
in Ǎꢁꢂꢃ−ꢇꢄ is the one that minimizes the mean squared error relatively to the considered  
∗
∗
ꢂꢎ ,ꢐ ꢄ  
ꢏ
ꢏ
blockꢑꢍꢂꢂꢎꢃꢄ,ꢐ ꢄ in a searche area ꢑꢕꢂꢃ−ꢇꢄ  
:
ꢏ ꢏ  
ꢂꢎ ,ꢐ ꢄ  
ꢏ
ꢏ
The illumination parameters are given by  
ꢂ
ꢄ
ꢂ
ꢄ
,
ꢏ
ꢞ
ꢞꢟꢓ  
,
ꢏ
̌
,ꢑꢙ  
ꢖ
ꢗꢘ  
ꢂꢑꢙ  
ꢚꢛ ,ꢜ ꢝ  
∀ꢅ ∈ ꢑꢍ(ꢎ ,ꢐ ), ĥ(ꢎ ,ꢐ )ꢄ(ꢅ ) ꢆ  
ꢚꢛ ,ꢜ ꢝꢑ  
(2)  
(3)  
ꢏ
ꢂ
ꢏ
ꢂ ꢄ  
ꢂ
ꢃ−ꢇ,ꢃ  
ꢃ
ꢁ
ꢁ
ꢔ
ꢠ
ꢏ
ꢏ
ꢏ
ꢏ
ꢄ
,
ꢞꢟꢓ  
ꢢ
ꢑꢡ  
,
ꢏ
ꢈꢛ ,ꢜ ꢋ  
ꢏ
ꢂ
ꢣꢂ  
ꢑꢌ(ꢎ ,ꢐꢄ)(ꢅ ) ꢆ ꢤ  
ꢥ ꢑĥ(ꢎ ,ꢐꢑ )ꢄ(ꢅ )ꢤ  
.
ꢃ−ꢇ  
ꢃ−ꢇ,ꢃ  
and  
ꢂ
ꢄ
ꢂ
ꢄ
,
ꢏ
ꢞ
ꢞꢟꢓ  
,
ꢏ
ꢁ
ꢁ
̌
ꢑꢙ  
ꢑꢙ  
ꢏ
ꢏ
ꢏ
ꢏ
ꢚꢛ ,ꢜ ꢝ  
ꢚꢛ ,ꢜ ꢝ  
ꢏ
ꢏ
Since most of the reported statistical tests require that analyzed data be normally  
ꢂ
ꢁ
ꢄ
ꢂ
ꢃ−ꢇ,ꢃ  
ꢆ ꢧꢑℎ(ꢎ ,ꢐ )ꢄꢨ  
is firstly transformed by using the Box-Cox  
ꢃ−ꢇ,ꢃ  
distributed, the set ꢑꢦꢂ ꢄ  
ꢏ
ꢏ
(ꢎ ,ꢐ )  
ꢏ
ꢏ
ꢄ
ꢂ
ꢃ−ꢇ,ꢃ  
ꢩꢂ  
ꢆ ꢧꢑℎ(ꢎ ,ꢐ )ꢄꢨ  
ꢃ−ꢇ,ꢃ  
ꢁ
̃
transformation [9]. This transformation give rise to the set ꢑꢦꢂ ꢄ  
ꢏ ꢏ  
(ꢎ ,ꢐ )  
ꢏ
ꢏ
ꢄ
ꢩꢂ  
ꢃ−ꢇ,ꢃ  
ꢁ
normally distributed. Then, in order to locate the outliers within ꢑꢦꢂ ꢄ  
, it is possible to  
apply one statistical test among the ones reported [10-11]. In this work, we retain the Minimum  
52  
Blotches detection  
Covariance Determinant (MCD) test for its efficiency and relatively low computational  
ꢂ
ꢁ
ꢄ
ꢃ−ꢇ,ꢃ  
complexity [10]. The MCD test provides a set ꢑꢪꢂ ꢄ  
of a typical values of the illumination  
coefficient that are asssociated to candidate blocks in Aj(k) and Aj(k-1) and are more susceptible to  
be blotched. The same procedure is carried out to detect suspicious blocks between Aj(k) and  
Aj(k+1). Only the blocks that are judged as suspicious in both the backward and the forward  
directions (by considering respectively the pairs (Aj(k-1), Aj(k)) and (Aj(k+1), Aj(k)) are retained for  
the final blotch detection step since blotches are considered as illumination variations occuring  
in both directions.  
2.2. Blotch detection  
Given the positions of the suspicious regions at different resolution levels, it is necessary  
to deduce the positions of the retained candidate regions at the initial resolution level. Since  
the goal behind resorting to a multiscale analysis is to handle the different sizes of the  
blotches, we consider a block at the initial resolution level as suspicious if it has been judged  
as such at, at least one resolution level initial resolution level. Since the goal behind resorting  
to a multiscale analysis is to handle the different sizes of the blotches, we consider a block at  
the initial resolution level as suspicious if it has been judged as such at, at least one resolution  
level ꢫ, ∀1 ≤ ꢫ ≤ ꢬ.  
The final step consists of detecting the corrupted pixels in each candidate region at the  
initial resolution of ꢭꢂꢃꢄ. For this purpose, one of the reported heuristic detectors as the SDIa,  
the ROD, the SROD, or the AR based detectors is used between suspicious blocks in ꢭꢂꢃꢄꢑand  
their homologous in the motion compensated refrence frames.  
2.3. Blotch removal  
We assume that the spots are identified and detected correctly in the previous step at this  
stage is a binary table, where the mottled pixel is color coded white and the rest black. This  
binary image is used to guide the recovery process. To remove blotches are detected, an  
approach based on the proposed inpainting. The performance of the solution is assessed  
subjectively or using some full reference image quality classical metrics like PSNR. In this  
work, we use hierarchical diagram similar to [12] and strategic global optimization. This  
approach introduces an effective performance and high quality output.  
(b) bloctch detection map  
(a) A blotched image  
(c) The initial priority map  
Figure 1. An example of the priority map  
53  
Nguyen Thi Quynh Hoa  
Firstly, a Gaussian pyramid was built from the original image to create hierarchical  
diagrams of input images. A set of images with different levels of detail can be created with  
ꢮꢯ ꢆ ꢭ as the input or original image. Number of pyramid levels depending on the original size  
of the image and the minimum resolution allowed. Then, a strategy used to fill in missing areas  
with the lowest resolution, ꢮꢰ. Athigher resolutions, inpainting problem are modeled as a  
graph optimization labels which help to show the selected label for each pixel unknown. It can  
be determined by optimizing the energy function optimization algorithm by global, multi-  
labeled graph cut [13]. A description of the algorithm removes spots is given in Figure 1.  
2.3.1. Correction of lowest resolution frame  
At lowest resolution, a template-based approach is used to remove the blob by using  
priority based on the window and choose the patch. Recommended removal methods work  
repeated as follows:  
- Detect spots: Identify spots and their boundaries based on the binary image. If no pixels  
in the spot, the algorithm is terminated due spots completely erased.  
- Define priorities edit: Calculator and randomly select a pixel p with the highest priority  
and determines a patch, P, gathered at p. In this work, we used the model of the most common  
priorities proposed in [14, 15] Combine the patch: Find a patch is not blurred, ꢱꢲ, similar to ꢱꢳ  
with mean squared error of pixel squares is not blurred.  
- Blotch removal: Fill in missing information in patch ꢱꢲ.  
- Information update: Update the binary mask image and return the step 1.  
Correction priority: So good priorities is essential because it directly affects the quality of  
the output. In this work, we used the model of the most common priorities proposed in [15] and  
it is defined as in Equation 4  
ꢴ
ꢂꢳꢄ  
ꢆ ꢵꢂ ꢄꢶꢂ ꢄ  
ꢑ
(4)  
ꢳ
ꢳ
where C(p) and D(p) denote confidence and data terms, respectively and they are defined as follows:  
∑
ꢖ
ꢂꢷꢄ  
ꢷꢸꢹ ∩ꢻ  
ꢺ
ꢵꢂꢳꢄ  
ꢆ
(5)  
(6)  
|ꢼ |  
ꢺ
ꢾ
ꢓ
ꢂ ꢄ  
ꢶ ꢽ ꢆ ꢾ +ꢿ  
ꢑ
ꢔ
During the initialization process, the values of reliability, C(p) is set to 0 for each pixel in  
blotched and 1 for others. ∈ is very small positive value, which ensures that terminology is  
always dominate the other. ꣀꢇ and ꣀ2 are two positive eigenvalues (ꣀꢇ≥ ꣀ2 ) determine the  
local changes of pixel intensities in each window Wp, gathered at p and is characterized by the  
following matrix:  
2
꣆꣇  
ꢚ ꢝ  
꣆꣈  
꣆꣇ ꣆꣇  
∑
ꢂ
ꢄ
ꣁꢂꢳꢄ  
ꢆ
ꢮꣂ ꣃ, ꣄ ꣅ  
꣆꣈ ꣆꣉2꣊ꢑ  
ꢚ ꢝ  
꣆꣉  
(7)  
ꢺ
꣆꣇ ꣆꣇  
꣆꣈ ꣆꣉  
꣆꣇  
where ꢮꣂ is a Gaussian window function calculates a total weight. The term data including  
ꢺ
structural features depends on the variation of two separate values. Figure 1 illustrates a  
preferred map said pixels will be restored first.  
Patch selection: The next step in the optimization algorithm is searching for patches  
matching the blurred area. In our work, a suitable patch is determined using similar  
54  
Blotches detection  
measurements on all pixels not faded in patches. Therefore, it is determined based on the  
difference of color and gradient as below:  
2
2
꣋
꣋
꣋
꣋
∑
ꢊ(Ψꢳ, Ψꢲ) ꢆ ꢚ(ꢭꢳ ꢥ ꢭꢲ) ꢉ ꣌(∇ꢭꢳ ꢥ ∇ꢭꢲ) ꢝꢑ  
(8)  
where Ip, Iq are the corresponding CIELab vectors; ∇ꢭꢳ, ∇ꢭꢲ represent the image gradient  
vectors. ꣌ is a user defined weight balancing the two terms. In our experiments, we used ꣌ ꢆ  
0.5. The patch with minimal distance to the source patch, ꢱꢳ, is the chosen one and given  
below:  
ꢱꢳ̂ ꢆ ꣍ꢅ꣎ꢤ꣏꣐꣑∈Φ{ꢊ(Ψꢳ, Ψꢲ)}ꢑ  
(9)  
2.3.2. Correction for higher resolution frame  
When finished creating images lowest resolution, compensation map is generated and  
used to reconstruct a higher resolution. Map offset determine the relationship between the pixel  
needs to be removed and the pixels in the region are not blurred are given below  
ꢂ
ꢄ
ꢕꣁꢂꢳꢄ ꢆ ꢧꢂ∆꣈,∆꣉ꢑꢳ ꣈,꣉ ∈Ω  
(10)  
ꢄ
ꢯ,ꢯ ꢑ꣒꣓꣔꣕꣖꣗꣋꣘꣕  
Compensation map obtained from the lower resolution is interpolated to higher resolution.  
However, the output image is derived directly from this map which contains annoying artifacts  
affect the nature of the images obtained. The authors of [16] the data and smoothness to refine  
compensation map. Energy function is defined as follows:  
ꢂ
ꢄ
ꢂ
ꢄ
ꢂ
ꢄ
ꢂ
ꢄ
ꢂ
ꢁ
ꢄ
ꢂ
ꢄ
ꢃ−ꢇ  
ꢃ−ꢇ,ꢃ  
ꢃ−ꢇ,ꢃ  
ꢃ−ꢇ  
ꢑḂ  
ꢆ ꣍ꢅ  
ꢂ
ꢄ
′
ꢏ
ꢄ
ꢤ꣏꣐  
ꢂ ꢄ  
ꢞ
ꢂꢀꢁꢃ (ꢅ ) ꢥ ꢑℎ Ǎꢁꢃ−ꢇ ꢈꢅ ꢉ ꢊ  
(ꢅ )ꢋ ꢥ ꢑꢌ(ꢎ ,ꢐ )ꢄ2ꢑ (11)  
∑
∈ꢑ꣙ꢂ  
꣖ꢏ∈ꢑꢙ  
ꢚꢛ ,ꢜ ꢝ  
ꢏ ꢏ  
(ꢎꢏ,ꢐꢏ)  
ꢞꢟꢓ  
′
ꢞꢟꢓ  
(ꢎꢏ∗,ꢐꢏ∗)  
ꢑḂ  
ꢁ
ꢁ
ꢁ
ꢏ ꢏ  
ꢚꢛ ,ꢜ  
ꢝ
ꢚꢛ ,ꢜ  
ꢝ
ꢏ
ꢏ
ꢏ
∑
∑
ꢂ
꣚ꣁ ꢆ ꣛ ꣚꣜(ꢕꣁꢂ ꢄ) ꢉ ꢂ1 ꢥ ꣛ꢄ ꢳ,ꢲ ∈ꢰꢙ ꣚꣘ꢂꢕꣁꢂ ꢄ, ꢕꣁꢂ ꢄ  
ꢄ
(12)  
ꢄ
ꢳ
ꢳ
ꢲ
where ꣚꣜ is a data term related to external requirements and ꣚꣘ is a smoothness term defined  
over a set of neighbouring pixels, N B. The parameter a is a user defined weight balancing the  
twoꢀtermsꢀsetꢀtoꢀαꢀ=ꢀ0.5ꢀinꢀourꢀexperiment.ꢀThe detail of the data term and smoothness term are  
given by equation (12), (13):  
∞
ꢂ꣈+∆꣈,꣉+∆꣉ꢄ∈Ω  
꣚꣜ꢂꢕꣁꢂ ꢄꢄ ꢆ ꢧ  
(13)  
ꢳ
ꢑ꣒꣓꣔꣕꣖꣗꣋꣘꣕  
ꢯ
whereꢀβꢀandꢀγꢀareꢀweightsꢀbalancingꢀtheseꢀtwoꢀterms,ꢀsetꢀtoꢀβꢀ=ꢀl,ꢀγꢀ=ꢀ2ꢀinꢀourꢀexperiment.ꢀThere  
are many approaches for minimizing this function. In the proposed method, a global  
optimization based on graph-cuts is developed because of the efficient implementation and the  
available source code. The alpha parameter is to determine the importance, or the balance  
between two operands. In this case, Ed and Es are chosen as 0.5 because these two operands are  
considered to have the same role, so they are equal.  
2.4. Experiment results  
This section is dedicated to the performance evaluation of the proposed framework.  
The performance of blotch detector scheme is evaluated in three round of simulation. The  
first round shows the benefits of versatile analysis versus monochrome case as in [7]. The  
second round presents a visual assessment using SROD detection in locating the damaged area  
candidates. And the last round is to evaluate the performance in comparison with the proposal in [17].  
ꢯ
ꢑ꣙  
=꣙꣞  
ꢂ ꢄ  
ꢷ
ꢂ
ꢺ
ꢄ
꣚꣘ꢂꢕꣁꢂ ꢄ, ꢕꣁꢂ ꢄꢄ ꢆ ꣝  
(14)  
ꢳ
ꢲ
ꢑ꣒꣓꣔꣕꣖꣗꣋꣘꣕  
꣟꣠꣞(꣙꣞ )+꣡꣠꣢ꢂ꣙꣞  
ꢂ ꢄ  
ꢺ ꢄ  
ꢂ
ꢄ
ꢺ
A sequence of thirteen frames has been used for testing. Frames are 720 × 576 pixels and  
encoded, which shows some typical frames to provide a visual demonstration of our proposal.  
55  
Nguyen Thi Quynh Hoa  
The first line contains some corrupted frames and the blotch detection is detected and  
represented by binary mask frames of the second line. The blotch removal frames are shown in  
the last line. In order to evaluate of performance the blotch removal algorithm, we compared  
with some state-of-the-art inpainting methods such as A. Criminisi et al. [14], Wu et al. [18] and  
Dang et al. [15]. The image quality of the proposed method has been objective evaluation with  
unclear quality indicators [19] and shown in Table 1. The higher the result are, the better the  
quality of the propose approach is.  
Table 1. The blotch removal quality metric  
Method  
Our proposal  
[15]  
[14]  
[18]  
Frame ID  
18  
20  
0.2159  
0.1987  
0.1178  
0.1391  
0.1078  
0.1735  
0.1711  
0.1928  
0.1934  
0.2382  
0.3363  
0.2382  
0.1429  
0.199  
0.2  
0.2118  
0.2022  
0.1234  
0.1286  
0.1102  
0.1705  
0.1577  
0.1825  
0.1946  
0.242  
0.2182  
0.2032  
0.1095  
0.1321  
0.1135  
0.1773  
0.1727  
0.1844  
0.1939  
0.2367  
0.3227  
0.2367  
0.1418  
32  
0.1105  
0.1248  
0.1075  
0.1724  
0.1591  
0.182  
37  
46  
50  
68  
85  
94  
0.1934  
0.2436  
0.3456  
0.2436  
0.1399  
102  
103  
111  
118  
0.3422  
0.242  
0.1395  
3. Conclusions  
The article has proposed a framework to detect and restore spots. The framework consists  
of two main stages: detection and recovery. For spot detection, a simple rank order difference  
(SROD) detector is proposed. Next, spots will be restored based on improved dimming printing  
techniques. The test results show an outstanding performance and expected results. The overall  
execution time of the schema is completely acceptable. In the future, we will improve and  
upgrade the framework to make it better with larger resolution videos.  
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