Blind People: Clothing Category Classification and Stain Detection Using Transfer Learning

Abstract

The ways in which people dress, as well as the styles that they prefer for different contexts and occasions, are part of their identity. Every day, blind people face limitations in identifying and inspecting their garments, and dressing can be a difficult and stressful task. Taking advantage of the great technological advancements, it becomes of the utmost importance to minimize, as much as possible, the limitations of a blind person when choosing garments. Hence, this work aimed at categorizing and detecting the presence of stains on garments, using artificial intelligence algorithms. In our approach, transfer learning was used for category classification, where a benchmark was performed between convolutional neural networks (CNNs), with the best model achieving an F1 score of 91%. Stain detection was performed through the fine tuning of a deep learning object detector, i.e., the mask R (region-based)-CNN. This approach is also analyzed and discussed, as it allowed us to achieve better results than those available in the literature.

1. Introduction

Vision is one of the senses that dominates our lives. It allows us to form perceptions of the surrounding world and give meaning to objects, concepts, ideas, and tastes [1]. Therefore, any type of visual loss can have a great impact on our daily routines, significantly affecting even the simplest tasks in our day-to-day habits. Vision loss can be sudden and severe, or the result of a gradual deterioration, where objects at great distances become increasingly difficult to see. Therefore, the wording “vision impairment” encompasses all conditions in which vision deficiency exists [2]. The individual who is born with the sense of sight and later loses it stores visual memories and can remember images, lights, and colors. This particularity is of the highest importance for re-adaptation. On the other hand, those who are born without the capacity of seeing can never form or possess visual memories. For both cases, clothing represents a demanding challenge.

Recently, there has been an increasing focus on assistive technology for people with visual impairments and blindness, aiming at improving mobility, navigation, and object recognition [3,4,5]. Despite the high technology already available, some gaps remain, particularly in the area of aesthetics and image.

The ways in which we dress and the styles that we prefer for different occasions are part of our identity [6]. Blind people do not have this sense, and dressing can be a difficult and stressful task. Taking advantage of the unprecedented technological advancements of recent years, it becomes essential to minimize the key limitations of a blind person when it comes to managing garments. Not knowing the colors, the types of patterns, or even the state of garments makes dressing a daily challenge. Moreover, it is important to keep in mind that blind people are more likely to have stains on their clothes, as they face more challenges in handling objects and performing simple tasks, such as eating, cleaning and painting surfaces, and leaning against dirty surfaces, among others. In these situations, most of the time, when we involuntarily drop something on our clothes that causes a stain, we immediately attempt to clean it, as we know that the longer we take to clean it, the greater the difficulty in removing the stain later—something that might happen more often with blind people.

Despite the already available cutting-edge technology and smart devices, some aspects of aesthetics and image still remain barely explored. This was the fundamental issue behind the motivation for this work—namely, how to enable blind people to feel equally satisfied with what they wear, functional, and without needing help. The scope of this research follows the previous work of the authors [7,8,9,10], as, through image processing techniques, it is possible to help blind people to choose their clothing and to manage their wardrobes.

In short, this work mainly contributes to the field with (i) the listing of relevant techniques used in image recognition for the identification of clothing items and for the detection of stains on garments; (ii) an annotated dataset of clothing stains, which could be later increased by new research; and (iii) a benchmark between different deep learning networks. The outcomes of this work are also foreseen to be implemented in a mobile application already identified as a preferred choice in a survey conducted with all departments of the Association of the Blind and Amblyopes of Portugal (ACAPO) [11].

Following the model approach already identified by the authors [12], the scope of the research presented here is focused on the algorithm for clothing category classification and stain detection. Alongside this, a mobile application and a mechatronic system, i.e., an automatic wardrobe, will complement all presented algorithms and methodology [13]. Taking advantage of the partnership with ACAPO and with the Association of Support for the Visually Impaired of Braga (AADVDB), the developed work was validated and opportunities for future improvements were identified. In the five upcoming sections, related work is described (Section 2), the methodology is explained (Section 3), experiments are described (Section 4) and the main conclusions and future work are finally presented (Section 5).

2. Related Work

In the last few years, deep learning techniques have arisen as a great method to solve problems in computer vision, such as image classification, object detection, face recognition and language processing, where convolutional neural networks (CNNs) play an imperative role [14].

The convolutional neural networks (CNNs) have exhibited excellent results and advances in image recognition since 2012 (CNNs) [15,16], when AlexNet [17] was introduced in the ImageNet Large Scale Visual Recognition Challenge (ILSVRC) [18,19]. The ImageNet competition consists of evaluating several algorithms for large-scale object detection and image classification, allowing researchers to compare detection across a variety of object classes. In recent years, several CNNs have been presented, such as VGG [20], GoogLeNet [21], SqueezeNet [22], Inception [23], ResNet [24], ShuffleNet [25], MobileNet [26,27], EfficientNet [28] and RegNet [29], among others, using these networks for different image classification problems.

In line with this premise, some researchers turned to the fashion world, making use of the more recent advances in computer vision to explore diverse areas such as fashion detection, fashion analysis and fashion recommendations, achieving promising results [30]. Based on the scope of the conducted research, only fashion classification is covered in this work. A quick literature survey allowed the identification of several works that have attempted to handle the classification of fashion images. Most of the authors evaluate their models based on top k accuracy regarding clothing attribute recognition, normally with top 3 and top 5 scores, which means that the correct label is among the top k predicted labels.

The research of Chen et al. [31] presented a network for describing people based on fine-grained clothing attributes, with an accuracy of 48.32%. Similarly, Liu et al. [32] introduced FashionNet, which learns clothing features by jointly predicting clothing attributes and landmarks. Predicted landmarks are used to pool or gate the learned feature maps. The authors reported a top 3 classification accuracy score of 93.01% and a top 5 score of 97.01%. Another method to detect fashion items in a given image using deep convolutional neural networks (CNN), with a mean Average Precision (mAP) of 31.1%, was performed by Hara et al. [33]. Likewise, Corbière et al. [34] proposed another method based on weakly supervised learning for classifying e-commerce products, presenting a top 3 category accuracy score of 86.30% and a top 5 accuracy score of 92.80%. Later, Wang et al. [35] proposed a fashion network to address fashion landmark detection and category classification with the introduction of intermediate attention layers for a better enhancement in clothing features, category classification and attribute estimation. In their work, accuracy scores of 90.99% and 95.75% were reported for top 3 and top 5, respectively. In another study by Li et al. [36], the authors presented a two-stream convolutional neural with one branch dedicated to landmark detection and the other one to category and attribute classification, allowing the model to learn the correlations among multiple tasks and consequently achieve improvements in the results. Accuracy scores of 93.01% and 97.01% for top 3 and top 5 were reported, respectively. A novel fashion classification model proposed by Cho et al. [37] improves the performance by taking into account the hierarchical dependences between class labels, reaching accuracy of 91.24% and 95.68% in top 3 and top 5, respectively. A multitask deep learning architecture was then proposed by Lu et al. [38] that groups similar tasks and promotes the creation of separated branches for unrelated tasks, with accuracy results of 83.24% and 90.39% for top 3 and top 5, respectively. Seo and Shin [39] proposed a Hierarchical Convolutional Neural Network (H-CNN) for fashion apparel classification. The authors demonstrated that hierarchical image classification could minimize the model losses and improve the accuracy, with a result of 93.3%. The research of Fengzi et al. [40] applied transfer learning using pertained models for automatically labeling uploaded photos in the e-commerce industry. The authors reported an accuracy value of 88.65%. Additionally, a condition convolutional neural network (CNN) was proposed by Kolisnik, Hogan and Zulkernine [41], based on branching convolutional neural networks. The proposed branching can predict the hierarchical labels of an image and the last label predicted in the hierarchy is reported with accuracy of 91.0%.

Table 1. Literature overview on fashion image classification works (adapted from [41]).

Author	Dataset	Year	Accuracy
Chen et al. [31]	Street-data	2015	Top 1: 48.31%
Liu et al. [32]	DeepFashion	2016	Top 3: 82.58%
Hara et al. [33]	Fashionista	2016	mAP: 31.1%
Lu et al. [38]	DeepFashion	2016	Top 3: 83.24%
Corbière et al. [34]	DeepFashion	2017	Top 3: 86.30%
Wang et al. [35]	DeepFashion-C	2018	Top 3: 90.99%
Li et al. [36]	DeepFashion-C	2019	Top 3: 93.01%
Cho et al. [37]	DeepFashion	2019	Top 3: 91.24%
Seo and Shin. [39]	Fashion-MINIST	2019	Top 1: 93.33%
Fengzi et al. [40]	Fashion Product Images	2020	Top 1: 88.65% 1
Kolisnik, Hogan and Zulkernine [41]	Fashion Product Images	2021	Top 1: 91.0% 1

¹ Results only reported for fashion classification accuracy.

summarizes the aforementioned works, including the used datasets.

Regarding the specific topic of stain detection, to the best of our knowledge, there are no relevant works available in the literature. Nonetheless, stain detection is an important sub-topic of defect detection in clothing and in the textile field; hence, considering a broader approach, i.e., defect detection in clothing and in the textile industry, some research works could be considered for comparative purposes.

C. Li et al. [42] recently developed a survey based on fabric defect detection in textile manufacturing, where learning-based algorithms (machine learning and deep learning) have been the most popular methods in recent years. The deep learning-based object detector is divided into one-stage detectors and two-stage detectors. One-stage detectors such as You Look Once (YOLO) [43] and the Single Shot Detector (SSD) [44] are faster but less accurate when compared with two-stage detectors, such as Faster R-CNN[45] and Mask R-CNN (region-based convolutional neural network) [46]. On the other hand, two-stage detectors are more accurate, but also slower. Thus, choosing an adequate algorithm is necessary for the envisioned application. Therefore, in the first stage, a more accurate detector was considered instead of a real-time need, since the detection of stains is affected by different sizes, aspects, and locations on clothes.

In sum, it is visible that there has been great effort to build efficient methods for fashion category classification. Moreover, the aforementioned works (Table 1) did not focus on developing systems to aid visually impaired people, and there is yet no solution capable of covering all the difficulties experienced by a blind person, namely an automatic system for clothing type identification and stain detection.

3. Methodology

In the pursuit of clothing type image classification and stain detection, a fundamental question arose: how can artificial intelligence enable the identification and inspection of clothing for blind people? The methodology implemented in this work aimed at answering this challenging question, and the dataset, deep learning techniques and evaluation metrics of the proposed solution are presented in the following sections.

3.1. Clothing Type Category Classification Methods

The clothing category classification is based on a public dataset. Prior to being submitted to a benchmark between several networks, the dataset is sorted and balanced for the same number of records. Then, utilizing data augmentation allows one to observe its influence on the results. This workflow is illustrated in Figure 1.

Detailed descriptions of each step of the workflow are provided in the following subsections.

3.1.1. Dataset

As previously mentioned, at an early stage, the goal was to identify the dataset that could fit the project needs. All images taken by blind people are placed in a controlled environment and with one item of clothing at a time [13].

The previous work carried out by the authors [12] allowed us to understand that more data are needed for training and to obtain more accurate results. Nevertheless, the results obtained with a fine-tuning process have shown that this could be a good approach for a small quantity of data. In this sense, a research survey was performed to look for available datasets; see

Table 2. Summary of available datasets for fashion category classification (adapted from [30]).

Dataset	Year	# of Photos	Description
DeepFashion-C [32]	2016	289,222	Annotated with clothing bounding box, pose variation type, landmark visibility, clothing type, category, and attributes.
Fashion Landmark Dataset [47]	2016	123,016	Annotated with clothing type, pose variation type, landmark visibility, clothing bounding box and human body joint.
FashionMinist [48]	2019	70,000	Grayscale image dataset associated with a label from 10 classes.
DeepFashion2 [49]	2019	491,000	A versatile benchmark of four tasks including clothes detection, pose estimation, segmentation, and retrieval.
Fashion Product Images [50]	2019	44,400	Annotated with gender, master category, subcategory, article type, base color, season, year, usage and product description.

.

Based on the characteristics of each dataset, it was decided to use the Fashion Product Images Dataset, namely the low-resolution version, as illustrated in Figure 1. It provides different attributes that meet the project’s current and further needs, such as category, color, and season of wear, among others. In addition, annotations with bounding boxes or clothing landmarks are avoided (since they do not fall within the scope of this work) and allow us to feed the dataset with more images without time-consuming annotations. However, despite the number of annotated features included in the dataset, it presents unbalanced data between article types, which were assumed as “categories” in this study. Figure 2 illustrates the clothes categories whose distribution had 500 records, i.e., each entry of the xx axis represents a specific category for which, at least, 500 images were considered.

To ensure a fair comparison between categories and to avoid imbalanced data, from the initial complete range, exactly 500 records were considered for each category depicted in Figure 1. An example of an item from each category is illustrated in Figure 3.

3.1.2. Transfer Learning for Clothing Type Classification

The main objective of image classification is to classify the image by assigning it to a specific label. It involves the extraction of features from the images.

CNNs have been used for different image classification problems. Most of them have a small quantity of data and training these networks carries a high computational cost and is a time-consuming task. With this premise, transfer learning appears as an interesting solution, where a pre-trained network is retrained with another dataset, allowing one to train a network faster than training from scratch. Transfer learning could be used in two different approaches, feature extraction and fine-tuning. Regarding the first one, the head of the network, the fully connected layer (FC), is replaced, and it only retrains this part. Moreover, all the weights of the convolutional layers of the network are frozen. On the other hand, in the second approach, the head of the network is replaced, and a new head can be built, which is similar to feature extraction. However, it differs from the first one as the weights of the convolution neural network can be unfrozen and the entire network can be retrained.

In this work, six implementations of convolutional neural networks were made, specifically those that, to the best of our knowledge, have never been used before in the Fashion Product Images Dataset. The choice of the implementation was based on the different depths and parameters; notwithstanding, all implementations had with the same resolution—see

Table 3. Main characteristics of pre-trained models.

CNN	Parameters (Millions)	Image Size (Pixels)
ResNet 50	25.6	224 × 224
ResNet18	11.7	224 × 224
MobileNetV2	66	224 × 224
GoogLeNet	7	224 × 224
MobileNet V3 Small	67.66	224 × 224
EfficientNet-B0	5.3	224 × 224

. Overall, this study used the following networks: RestNet-18, ResNet-50, MobileNetV2, GoogLeNet, Mobilenet V3 (small) and EfficientNet-B0. A comparative analysis of the results obtained with these networks was also carried out.

3.1.3. Evaluation Metrics

As already explained in Section 2, most authors evaluate their models with top 3 and top 5 scores, meaning that the correct label is among the top k predicted labels. Nevertheless, the top 1 score is required in this work due to the practical application in sight, which translates to the fact that the predicted class with the highest probability is the same as the target value.

As a result, it is necessary to use the following metrics.

• Accuracy (acc), i.e., the relation of correctly predicted observations to the total observations:

$$\mathrm{acc}=\frac{\mathrm{TP}+\mathrm{TN}}{\mathrm{TP}+\mathrm{FP}+\mathrm{FN}+\mathrm{TN}},$$

(1)

• Precision (P), i.e., the relation of correctly predicted positive observations to the total predicted positive observations:

$$\mathrm{P}=\frac{\mathrm{TP}}{\mathrm{TP}+\mathrm{FP}}$$

(2)

• Recall (R), i.e., the relation of correctly predicted positive observations to the observations in the actual class:

$$\mathrm{R}=\frac{\mathrm{TP}}{\mathrm{TP}+\mathrm{FN}}$$

(3)

• F1 score, i.e., the weighted average of precision and recall:

$$\mathrm{F}1\mathrm{Score}=2\ast \frac{\mathrm{P}\ast \mathrm{R}}{\mathrm{P}+\mathrm{R}}$$

(4)

where TP, FP and FN represent, respectively, the number of true positives (TP), false positives (FP) and false negatives (FN).

3.2. Stain Detection Methods

The stain detection process involves the creation of a dataset and its annotation. A neural network is then applied to the dataset, using fine-tuning, for stain detection. Figure 4 depicts the entire workflow process.

The following subsections provide descriptions of each step of the workflow.

3.2.1. Dataset

To the best of our knowledge, there is no public dataset on clothes with stains available. Therefore, a new dataset with ca. 104 images was built and named the “stains dataset”; it was then divided into a training set and a validation set. The training dataset comprised 80% of the images, while the remaining 20% served as an evaluation set to determine the model’s accuracy. Each article of clothing could have multiple stains dispersed across different parts of the garment, resulting in a total of ca. 300 stains. The images used in the “stains dataset” were collected from personal wardrobes, where coffee and wine stains were applied on clothes, as depicted in Figure 5.

An automatic wardrobe is currently being developed to allow the clothes to be placed in standardized positions, with which blind people can take photographs under the same controlled conditions [13].

3.2.2. Transfer Learning for Stain Detection

Regarding stain detection, using deep learning, the segmentation and classification heads of Mask R-CNN were trained through Detectron2, a Pytorch-based modular object detection tool. Detectron2 has shown better results on benchmarks compared to other Mask R-CNN implementations. Mask R-CNN is an extension of Faster R-CNN, since it is enhanced with the introduction of instance segmentation.

Despite garments having two types of stains, the annotation process was done with only one class, i.e., a stain. In order to use transfer learning, the weights file mask_rcnn_R_50_FPN_3x with ResNet50 was used as a backbone.

3.2.3. Evaluation Metrics

An evaluation of the proposed methodology was conducted based on the average precision (AP). The AP was measured using an IoU threshold of 0.50 and 0.75, as expressed in Equation (5):

$$\mathrm{IoU}=\frac{\mathrm{Area} \mathrm{of} \mathrm{Overlap}}{\mathrm{Area} \mathrm{of} \mathrm{Union}}$$

(5)

with respect to the previous IoUs, precision and recall can be calculated by means of Equations (2) and (3), respectively, by calculating the number of true positives (TP), false positives (FP) and false negatives (FN).

Finally, a precision–recall curve (PR) for the object class is generated, and the area under the curve represents the average precision (AP) of the model.

4. Experiments and Results

This section presents the results of the experiments conducted for the classification of category types and stain detection.

4.1. Clothing Type Category Classification

A total of three experiments were initially conducted using the Fashion Product Images Dataset. The two first experiments were based on fine-tuning, while the third experiment relied on feature extraction. In order to perform a comparison between all networks, the training and validation parameters were unchanged.

Table 4. Hyper-parameters of model experiments.

Parameters	Value
Optimizer	SGD
Momentum	0.9
Leaning rate	0.001
Batch size	16

describes the hyper-parameters.

The epochs were the only change between networks due to their architecture and targeting the best performance. The cross-entropy loss (Equation (6)) allowed us to measure how well a classification model performed, providing a probability value between 0 and 1:

$${\mathrm{L}}_{\mathrm{CE}}=-{\displaystyle \sum }_{\mathrm{i}=1}^{\mathrm{n}}{\mathrm{t}}_{\mathrm{i}}\log \left({\mathrm{p}}_{\mathrm{i}}\right), \mathrm{for} \mathrm{n} \mathrm{classes},$$

(6)

where t_i is the truth label and p_i is the Softmax probability for ith class.

These networks were implemented using the Pytorch library and trained using an NVIDIA A100 running Ubuntu 20.04.2 LTS.

Table 5. Test performance results.

Network	Train Accuracy	Validation Accuracy	Train Loss	Validation Loss	Epochs	Time (s)
ResNet-50	0.946	0.903	0.159	0.296	4	153.72
ResNet-18	0.939	0.904	0.183	0.279	4	111.66
MobileNet V2	0.917	0.898	0.233	0.290	4	139.04
GoogLeNet	0.940	0.907	0.189	0.279	7	266.20
MobileNet V3 (small)	0.917	0.883	0.234	0.327	7	241.66
EfficientNet-B0	0.927	0.900	0.210	0.295	12	539.59

reports the fine-tuning results using pre-trained neural networks.

During the fine-tuning process, the entire network is trained, meaning that all the layers’ weights are trainable. However, the weights of batch normalization—a network layer inserted between hidden layers—are set to non-trainable to prevent the network from learning new batch normalization parameters, i.e., beta and gamma [51]. These batch statistics are likely to differ greatly if the fine-tuning examples differ from those in the original training dataset. As a result of the small size of the fine-tuning dataset, it is not always desirable to re-learn these parameters during fine-tuning. The results presented in Table 5 reveal that GoogLeNet had the highest validation accuracy, of 90.7%, with almost all networks presenting close validation accuracy values. Only MobileNet V3 presented a notably lower accuracy value, i.e., 88.3%.

In addition, in the fine-tuning process, the depth between the same architectures (ResNet-18 and ResNet-50) for this dataset was not relevant, achieving approximately the same results, with 90.4% and 90.3% validation accuracy values, respectively. Moreover, the increase in the depth leads to more time consumption, and the number of epochs needed to achieve approximately the same results is equal. The depth between networks, as well as the parameters, does not show any correlation with the accuracy of them.

The inference time was then evaluated for each network. For this, the synchronization time between the CPU and GPU was considered and 400 iterations of GPU warm-up were implemented.

Table 6. Inference time by network architecture.

Network	Time (ms)	Standard Deviation
ResNet 50	0.0126	0.251
ResNet18	0.0081	0.162
MobileNetV2	0.0117	0.235
GoogLeNet	0.0169	0.338
MobileNet V3 Small	0.0120	0.239
EfficientNet-B0	0.0197	0.394

summarizes the average time and the standard deviation for 400 inferences of the same image, and for each network.

The results presented in Table 6 indicate that ResNet-18 allows us to achieve the best inference time. Moreover, these results allow us to infer that the inference time does not depend either on the number of parameters or on different network architectures. Furthermore, the standard deviation appears to be correlated with the inference time, as it increases with the inference time.

In the second experiment, data augmentation was introduced, namely random horizontal flip and random rotation, which normally leads to improvements in the model. The obtained results are described in

Table 7. Test performance results with augmented data.

Network	Train Accuracy	Validation Accuracy	Train Loss	Validation Loss	Epochs	Time (s)
	With Random Horizontal Flip
ResNet-50	0.958	0.906	0.112	0.307	6	262.63
ResNet-18	0.950	0.907	0.146	0.275	6	162.28
MobileNet V2	0.927	0.910	0.201	0.271	6	228.77
GoogLeNet	0.941	0.911	0.171	0.272	10	356.57
MobileNet V3 (small)	0.911	0.893	0.251	0.320	7	223.88
EfficientNet-B0	0.921	0.903	0.223	0.276	13	542.21
	With Random Rotation (90)
ResNet-50	0.934	0.887	0.187	0.323	11	364.47
ResNet-18	0.914	0.887	0.238	0.339	10	272.93
MobileNet V2	0.911	0.887	0.245	0.334	12	464.70
GoogLeNet	0.908	0.894	0.269	0.306	14	509.61
MobileNet V3 (small)	0.896	0.880	0.281	0.379	15	481.10
EfficientNet-B0	0.896	0.880	0.295	0.321	18	804.20
	With Random Horizontal Flip and with Random Rotation (90)
ResNet-50	0.947	0.887	0.148	0.328	15	508.69
ResNet-18	0.904	0.885	0.260	0.331	11	306.74
MobileNet V2	0.908	0.884	0.255	0.334	13	539.59
GoogLeNet	0.903	0.883	0.259	0.325	17	608.41
MobileNet V3 (small)	0.899	0.880	0.271	0.369	17	533.98
EfficientNet-B0	0.908	0.891	0.254	0.304	25	1041.29

.

Based on the results in Table 7, it can be concluded that amongst data augmentation, the random horizontal flips feature effectively contributed to the improvement in the model’s performance. As in the first experiment, GoogleLeNet allowed us to obtain the best accuracy value (91.1%) and MobileNet V3 (small) resulted in the lowest accuracy value (89.3%). Finally, augmented data with random rotation resulted in poor performance. Following this, the precision, recall and F1 score obtained for the GoogLeNet network are presented in

Table 8. Classification report of the GoogLeNet network.

Network	Precision	Recall	F1 Score	Support
Backpacks	0.99	0.96	0.98	110
Belts	1.00	1.00	1.00	102
Briefs	1.00	0.99	0.99	96
Casual Shoes	0.81	0.75	0.78	102
Flats	0.71	0.61	0.66	107
Flip Flops	0.88	0.94	0.91	124
Formal Shoes	0.98	0.94	0.96	104
Handbags	0.95	0.92	0.94	91
Heels	0.66	0.77	0.71	97
Jeans	0.99	0.90	0.95	115
Kurtas	0.93	0.95	0.94	101
Perfume and Body Mist	1.00	0.99	0.99	90
Sandals	0.86	0.83	0.84	105
Shirts	0.91	0.94	0.92	96
Shorts	0.98	0.99	0.98	96
Socks	0.97	0.99	0.98	90
Sports Shoes	0.81	0.86	0.83	90
Sunglasses	1.00	1.00	1.00	96
Tops	0.83	0.88	0.85	105
Trousers	0.88	0.98	0.92	88
T-Shirts	0.93	0.83	0.88	90
Wallets	0.95	0.97	0.96	107
Watches	0.98	0.99	0.98	97
Accuracy			0.91	2299
Macro avg	0.91	0.91	0.91	2299
Weighted avg	0.91	0.91	0.91	2299

. Complementarily, Figure 6 depicts the confusion matrix of the model with the best result based on the performance measurements (GoogLeNet). The confusion matrix allows the visualization of the performance of the classification model.

Independently of the good performance of the model, it is worth noting that there are some misclassifications between similar clothing articles, such as casual shoes and sport shoes, heels and flats, and t-shirts and tops (Figure 6).

The third experiment employed transfer learning via feature extraction, where the weights of all layers are frozen, except the output layer. The obtained results show that the loss of the network is ca. 90 %, and it is therefore not viable.

Thus, the results show that using a pre-trained network, the fine-tuned GoogLeNet with augmented data, with proper hyper-parameters, effectively outperforms the work proposed by Fengzi et al. [40]. Comparatively, the obtained results can be explained by the fine-tuning of all network layers, leveraging the pre-trained weights of all architectures and replacing only the last layer, which differs from Fengzi et al. [40], where new head layers were added. Moreover, in this study, the various augmentations were tested in order to assess their contribution, with rotation having the greatest impact on the reduced performance, and the horizontal flip having the greatest impact on the increased performance. Contrarily, Fengzi et al. [40] combined all augmentations during the training process.

The accuracy of this study is similar to that obtained by Kolisnik, Hogan and Zulkernine [41], although the number of classes considered is not mentioned.

4.2. Stain Detection

At this stage of the work, the Detectron2 library was used with the implementation of Mask R-CNN for stain detection. The hyper-parameters are stated in

Table 9. Hyper-parameters for fine-tuned Mask R-CNN.

Parameters	Value
Iterations	360
Leaning rate	0.001
Batch size	1

.

As briefly discussed, this network has advantages over Faster R-CNN as a result of the addition of pixel-level segmentation, i.e., labeling every pixel that belongs to the detected object. This benefit is easily perceptible in Figure 7, which shows an example of stain detection, where the bounding box around the stain is visible, as well as its pixel level.

An experiment was conducted that addressed only the detection of stains, rather than the distinction between them. The main results of the network performance and model losses from Mask R-CNN are presented in

Table 10. Results from Common Objects in Context (COCO) evaluator.

Network	AP	AP at IoU = 0.50	AP at IoU = 0.75
Bounding Box	0.549	0.857	0.672
Segmentation	0.540	0.858	0.674

and

Table 11. Summary of model losses.

Total Loss	Loss Classification	Loss Box Regression	Loss Mask
0.480	0.053	0.154	0.240

, respectively.

Through the COCO evaluator, it is possible to verify that despite the small quantity of data, the presented results are promising, especially regarding the AP at IoU = 0.50 of 0.857 (Table 10). The highest verified loss was 0.240 (Table 11), indicating a more challenging task related to the segmentation of the stain.

The evaluation of the model allowed us to conclude that the misclassifications were mainly related to the detection of brand logos in the clothing and the low contrast between the stain and the clothing color, as shown in Figure 8.

5. Conclusions

Blind people experience challenging difficulties regarding clothing and style on a daily basis, something that is often essential to an individual’s identity. Especially regarding stain detection in clothing, blind people need supporting tools to help them to identify when a clothing item has a stain, as cleanliness is often important for a person to feel comfortable and secure in their appearance. Such difficulties are often overcome with the help of family or friends, or others with great organizational capacity. However, for a blind person to feel self-confident in their clothing, the use of technology becomes imperative, namely the use of neural networks.

In this study, an analysis of clothing type identification and stain detection for blind people is presented. Through the transfer learning benchmark results, a deep learning model was demonstrated to be able to identify the clothing type category with up to a 91% F1 score, representing an improvement in comparison to the literature. Augmented data were proven to potentially improve even further the obtained results. Nevertheless, more tests should be performed in order to identify which type of augmented data fits better the model considered in this work.

A pioneering method to detect stains from a given clothing image was also presented based on a dataset comprising clothing with wine and coffee stains. This dataset was built to demonstrate that the proposed deep learning algorithm could accurately detect and locate stains on clothing autonomously. The results were promising and are expected to improve when a larger dataset is used.

This work was somehow limited by the fact that clothing type recognition was based on clothing worn by models, which can lead to an unwanted loss in the model and to categories that are not necessary due their redundancy. On the other hand, the stains dataset can be improved with more data and with the optimization of the number of categories considered for clothing type detection. Additionally, the development of a mobile application and its subsequent validation with the blind community can be performed, allowing these results to be integrated into an automatic wardrobe.

Nevertheless, the overall concept behind this work was fully demonstrated, as a system that can significantly improve the daily lives of blind people was developed and tested, allowing them to automatically recognize clothing and identify stains.