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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Art with Deep Learning</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Tommaso Bianco</string-name>
          <email>t.bianco5@studenti.uniba.it</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Giovanna Castellano</string-name>
          <email>giovanna.castellano@uniba.it</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Rafaele</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Department of Computer Science, University of Bari Aldo Moro</institution>
          ,
          <addr-line>Bari</addr-line>
          ,
          <country country="IT">Italy</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2023</year>
      </pub-date>
      <abstract>
        <p>Generative AI, mainly through Difusion Models, has revolutionized art creation, blurring the distinction between human and AI-generated art. This study introduces a novel dataset comprising human-made and AI-generated art and employs Deep Learning models (VGG-19, ResNet-50, ViT) to distinguish between them. We also use eXplainable AI techniques to derive insights. Our results highlight the potential of AI to detect machine-generated content, with implications for art authentication.</p>
      </abstract>
      <kwd-group>
        <kwd>Computer vision</kwd>
        <kwd>Deep learning</kwd>
        <kwd>Digital humanities</kwd>
        <kwd>Generative AI</kwd>
        <kwd>Synthetic art</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Art has undergone a profound transformation with the emergence of generative Artificial
Intelligence, notably driven by technologies such as Generative Adversarial Networks [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ] and
the increasingly popular Difusion Models [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. These groundbreaking innovations have pushed
the boundaries of artistic creation, empowering machines to produce remarkably lifelike images,
including paintings, that challenge our conventional notions of human creativity. Indeed,
generative AI has exhibited the capability to generate synthetic paintings that closely emulate
renowned artists’ styles, brushwork, and aesthetics. This level of fidelity in replicating the
artistic process blurs the demarcation between traditional, human-crafted art and
machinegenerated creations.
      </p>
      <p>The distinction between genuine human-made art and its synthetic counterparts carries
extensive implications, influencing aspects such as art authentication, valuation, and preservation
while igniting debates concerning technology’s role in the creative process. While
conventional methods of art connoisseurship traditionally relied on expert human judgment, the rapid
evolution of Deep Learning models and the availability of extensive art datasets present new
avenues for addressing this challenge. One intriguing approach to detecting instances
generated by machines, in fact, involves leveraging the capabilities of machines themselves. This
concept is rooted in the idea that the same AI technologies responsible for creating synthetic
content can also be employed for their detection and diferentiation from authentic human-made
counterparts. Deep Learning and Computer Vision algorithms can also be trained on large
datasets containing authentic and AI-generated examples. These models can learn to identify
nEvelop-O
∗Corresponding author.
subtle patterns, inconsistencies, or artifacts that may indicate machine generation. By utilizing
AI-powered classification models, we can automate the process of detecting machine-generated
content, achieving both eficiency and accuracy.</p>
      <p>
        Given these considerations, this paper distinguishes between authentic and synthetically
generated artworks. This efort begins with creating a novel dataset and proceeds to conduct
experiments that evaluate well-established Deep Learning algorithms, including VGG-19 [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ],
ResNet-50 [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ], and Vision Transformers (ViT) [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. Furthermore, we complement our quantitative
analysis with qualitative examinations using eXplainable AI frameworks, particularly
GradCAM [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. This approach can help visually justify why a given algorithm classifies an image as
real or synthetic, shedding light on the most discriminative image regions.
      </p>
      <p>The rest of this paper is structured as follows. Section 2 reviews the existing literature on
recognizing synthetic images. Section 3 introduces our proposed dataset. Section 4 details the
classification method proposed for this task. Section 5 provides insights into the experiments
conducted in this research. Finally, Sec. 6 concludes the article while highlighting potential
directions for future research eforts.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work</title>
      <p>
        In recent years, there has been a significant surge in interest in Deep Learning-based models,
particularly in image analysis. Notably, the emergence of Difusion Models, as exemplified in
the review paper by Croitoru et al. [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ], has yielded remarkable outcomes in generating
highifdelity images full of authentic details. However, generative models are often characterized by
discernible idiosyncratic patterns, which can be exploited to ascertain an image’s genuineness.
Despite concerted eforts to mitigate the presence of such patterns within Difusion Models, it is
imperative to acknowledge that they are not entirely free of such distinctive traits. Specifically,
research has underscored the significance of features such as color band inconsistency [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] and
the paucity of variation in color intensity [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] in identifying synthetic images.
      </p>
      <p>
        Consequently, various Computer Vision techniques have been harnessed to facilitate the
automated detection of the factors mentioned above. Guo et al. [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] and Guarnera et al. [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]
have introduced hierarchical fine-grained classification methodologies explicitly designed to
discriminate between forged or synthetic images. Central to their approach is the meticulous
curation of a training dataset, wherein the hierarchical framework necessitates the
comprehensive incorporation of diverse forgery techniques. This endeavor, however, poses a challenge,
particularly in scenarios characterized by limited diversity within the available training data.
Addressing the recognition of semantic and stylistic features in images, Amoroso et al. [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] have
tackled the issue of discerning synthetic images that exhibit heightened distinctiveness within
the stylistic domain. Nonetheless, the practical implementation of semantic-style
disentanglement presents notable challenges, primarily requiring the development of bespoke training
datasets tailored explicitly to this specific objective. Hamid et al. [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] proposed a framework for
fake image detection based on ResNet, achieving good results on a dataset containing real and
fake images generated by GANs.
      </p>
      <p>
        In the digital humanities domain, identifying forgeries, often manifesting as synthetic images,
holds paramount significance for art experts. This task tests whether a given artwork is an
authentic painter’s creation or a generative algorithm’s output. Nevertheless, the scrutiny
of fine arts presents demanding challenges due to the intrinsic variability and subjectivity
inherent in the data. Notably, similar objects may be rendered in divergent artistic styles,
while conversely, a singular artwork can evoke disparate emotional reactions among diferent
observers. In response to this complexity, numerous models tailored for artwork analysis have
embraced a multimodal approach, accommodating various data inputs such as images, text
descriptions, or structured knowledge graphs. For example, in [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ], we proposed a multimodal
neural architecture adept at combining visual and contextual features from artworks, thereby
facilitating the identification of their style and genre. Similarly, Bose et al. [ 14] presented a
Transformer-based architecture to perform sentiment analysis within visual arts. This model
efectively integrates visual features extracted from images with textual embeddings derived
from painting descriptions.
      </p>
      <p>
        However, it is noteworthy that a scarcity of scholarly literature addresses the automated
detection of AI-generated artworks. In light of this, the present study contributes by
introducing a novel dataset, which encompasses both authentic pieces of art, obtained through
    ℎ [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ], and synthetic artistic images, sourced from ArtiFact [15]. Our study then
assesses how well-established Deep Learning models can diferentiate between them.
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Materials</title>
      <p>
        In order to conduct valuable experiments to recognize synthetic works of art, we designed a new
large-scale dataset consisting of authentic and generated artworks. Specifically, we exploited
two datasets:     ℎ [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ] and ArtiFact [15]. The former is a knowledge graph specializing
in art, representing diferent concepts related to artworks and artists. It contains 116, 475 art
pieces, divided into 32 styles and 18 genres. Instead, ArtiFact is a large-scale dataset containing
2, 496, 738 images, comprising 946, 989 authentic images and 1, 531, 749 fake images, concerning
diferent domains, which include but are not limited to human faces, animals, vehicles, and
art. To ensure significant diversity in the data, the authors have randomly sampled images
from multiple data sources for authentic images, whereas, concerning synthetic content, they
have exploited captions and image masks from the COCO dataset [16], which were passed to
text2image and inpainting models. Furthermore, the authors employed various random seeds
to sample normally distributed noise, which was then used to generate additional images using
generative models. These images underwent cropping with a fixed ratio of 5/8, ensuring the
crop size fell within 160 to 2048 pixels. Lastly, all the images were resized to a uniform resolution
of 200 × 200 pixels and saved in JPEG format.
      </p>
      <p>To collect data, we first extracted all the synthetic images of art within the ArtiFact dataset.
This way, we gathered a set of images consisting of 37, 775 synthetic works of art generated
by multiple algorithms (e.g., Stable Difusion [ 17] and StyleGAN [18]). Whereas, for authentic
artworks, we sampled 50, 000 artworks from     ℎ , stratifying this process on the style
attribute to avoid extreme class imbalance. Figure 1 shows two images representing each class
within our dataset. Interestingly, there appears to be little distinction between the authentic
and generated images. This observation underscores the primary motivation driving our study.
“Landscape”
by Janos Mattis-Teutch
“Nude on green sofa”</p>
      <p>by M. H. Maxy</p>
    </sec>
    <sec id="sec-4">
      <title>4. Methods</title>
      <p>
        This research presents a comprehensive Computer Vision framework centered around binary
classification algorithms. To thoroughly evaluate the characteristics of this task, we conducted
experiments using three cutting-edge techniques: VGG-19 [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ], ResNet-50 [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ], and ViT [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ].
      </p>
      <p>Figure 2 depicts the architecture of VGG-19, which we selected due to its capability to
acquire hierarchical features from input images. This characteristic allows it to capture complex
patterns and representations efectively. Moreover, the VGG-19 architecture is characterized by
its simplicity and uniform structure, comprising convolutional and max-pooling layers. In Fig. 3,
we present the conceptual design of the ResNet-50 model. This neural network introduces the
concept of “residual learning”, incorporating skip connections that facilitate the smoother flow
of information throughout the network and address the vanishing gradient problem. Lastly,
Fig. 4 provides an overview of the ViT architecture, a state-of-the-art model recognized for
its exceptional performance in various Computer Vision tasks, including image classification.
ViT’s scalability makes it suitable for tasks involving images of varying sizes, as it allows for
adjustments to the patch size and the number of layers, adapting to diferent input dimensions
and computational resources.</p>
      <p>In all cases, we leverage transfer learning to train the models mentioned above by freezing
all feature extraction layers and letting the model optimize just the last fully connected layers,
distinguishing whether the given image is an authentic artwork or a synthetic one. Accordingly,
once visual information is computed by each backbone, the feature vector is fed into a
sigmoidactivated fully connected output layer, representing the probability that the given image is
authentic. Then, to optimize the model, we use a binary cross-entropy loss function:
ℒ = 1</p>
      <p>=1</p>
      <p>∑ ℓ (  ,  ̂ ),
where  is the number of instances in the training set,   is the true label,  ̂ is the model outcome,
and ℓ (  ,  ̂ ) = −(  log( ̂ ) + (1 −   ) log (1 −  ̂ )) is the classic binary cross-entropy loss.</p>
      <p>
        We employed Grad-CAM, a technique introduced by Selvaraju et al. in [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ], to enhance
the explanatory aspect of our inference process. This approach allows us to shed light on
the decision-making process of a typical Computer Vision method. Grad-CAM leverages
the gradients associated with the network’s output concerning the feature maps in the last
convolutional layer. As a result, we empower users to visualize the image patches that exert
the most significant influence, which are highlighted in red. This feature amplifies the model’s
usefulness, especially in a hypothetical collaborative system involving humans and AI, where
informative automated suggestions can expedite decision-making.
      </p>
    </sec>
    <sec id="sec-5">
      <title>5. Experiments</title>
      <p>We performed some experiments for all the models mentioned above from both quantitative
and qualitative points of view. In this section, we describe the experimental setup and discuss
the obtained results.</p>
      <sec id="sec-5-1">
        <title>5.1. Experimental Setup</title>
        <p>The experiments were conducted using the Google Colab framework. Its resources include an
Intel Xeon processor, 12 GB of RAM, and an NVIDIA T4 GPU with 15 GB of VRAM. All the
models were implemented using the popular PyTorch library, which is well-known and suited
for Computer Vision research.</p>
        <p>We adopted an 80/10/10 splitting criterion, stratifying the partitioning on the target class.
In this way, we ensured that the data distribution was preserved among training, validation,
and test sets. It is worth noting that we used the same splitting to train all three models to
have a fair comparison. Furthermore, all the images were preprocessed via center cropping. We
resized them to a standard size of 224 × 224 pixels and performed normalization using the mean
and standard deviation values of the ImageNet dataset. It is worth noting that all images (real
and synthetic) were processed in the same way to conduct a fair experiment. Regarding the
optimization stage, we used the Adam optimizer with a learning rate of 10−3 and a batch size of
32. An early stopping callback was introduced in the training loop with a patience of 3 and a
learning rate schedule based on reducing it on the plateau to avoid overfitting.</p>
        <p>To evaluate the efectiveness of the models, we used diferent performance metrics. Accuracy
was calculated to show the percentage of well-classified instances. Furthermore, we
calculated precision, recall, and F1-score to evaluate the model’s trustworthiness in identifying the
authentic and the generated art pieces precisely.</p>
      </sec>
      <sec id="sec-5-2">
        <title>5.2. Results</title>
        <p>The quantitative results of the experimental analysis are shown in Table 1. The table shows
that all three models are good predictors, with all metrics above 95%. The best model is ViT, but
VGG-19 and ResNet-50 also perform well. These results highlight the ability of these models
to detect subtle and imperceptible patterns that allow them to correctly distinguish between
authentic and synthetic artworks, even though this would be a very challenging task for the
naked eye.</p>
        <p>Furthermore, in terms of qualitative evaluation, we assessed the models by analyzing their
Grad-CAM outputs. Firstly, in Fig. 5, we present examples where the models correctly classified
the images. Notably, VGG-19 emphasizes broad, coarse-grained features that span extensive
areas within the given image. In contrast, ResNet-50 and ViT focus more on fine-grained details,</p>
        <p>Input</p>
        <p>VGG-19</p>
        <p>ResNet-50</p>
        <p>ViT
distinguishing whether a patch appears authentic or generated. In most cases, the models
highlight image regions containing color discrepancies or lines that deviate from established
patterns found elsewhere in the image. These discernible patterns are also noticeable in
misclassified images, as depicted in Fig. 6. VGG-19, in these instances, emphasizes nearly half of
the image, indicating confusion in its analysis. ResNet-50 directs attention to details in the sky
where the pattern does not match the specific patch. Finally, ViT focuses on irregular lines
within the eye. These observations highlight the inherent challenges in this task. Factors such
as degradation over time or imperfections in the original artwork, such as inaccurately drawn
lines by the artist, may contribute to these challenges.</p>
        <p>From a conceptual standpoint, the suggested model accentuates image patches that deviate
from the overall visual context. It considers broad and subtle features, including those that
might not be immediately apparent to the naked eye. This discrepancy can be attributed to
artifacts left in the image by generative models, which other algorithms can discern.</p>
        <p>Grad-CAM heatmap</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusion</title>
      <p>In this paper, our focus was recognizing artificial artworks generated by AI systems using Deep
Learning models. To achieve this, we curated a novel dataset that included both authentic
and generated artworks. We then experimented with various neural network architectures
and conducted a comprehensive evaluation, considering both quantitative and qualitative
aspects. Specifically, our quantitative analysis revealed that Vision Transformers exhibited
strong predictive capabilities for this particular task, surpassing the performance of well-known
models like VGG-19 and ResNet-50. Furthermore, it is worth noting that none of the three
models misclassified the same test instances. However, upon closer examination of misclassified
cases, we acknowledged that subtle imperfections at a fine-grained level could influence the
models’ ability to identify synthetic artworks correctly.</p>
      <p>
        Future work could systematically compare the proposed method against other techniques
designed for fake image detection, as the current work is exploratory in nature. Additionally,
analyzing feature importance from a semantic perspective would improve model interpretability
and move beyond pure visual interpretations of activation maps. Also, integrating contextual
cues could help performance, as prior work has shown this modality to be efective for analyzing
artistic metadata [
        <xref ref-type="bibr" rid="ref13">13, 19</xref>
        ]. Finally, ensemble approaches may be explored to harness the combined
strengths of multiple models and enhance overall efectiveness for this task.
The research of Rafaele Scaringi is funded by a Ph.D. fellowship within the framework of the
Italian “D.M. n. 352, April 9, 2022” - under the National Recovery and Resilience Plan, Mission
4, Component 2, Investment 3.3 - Ph.D. Project “Automatic analysis of artistic heritage via
Artificial Intelligence”, co-supported by “Exprivia S.p.A.” (CUP H91I22000410007).
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    </sec>
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