• Archives of design research
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• v.16 no.4
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• pp.481-488
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• 2003

A method to select the proper file formats of thumbnail images is proposed. After the experimental works for image file formats such as JPEG, GIF, and those effectiveness to the features contained in images, four features are obtained by feature extraction methods used in contents based image indexing, those are, the details, highly saturated colored area, the number of clustered color, and the amount of continuously varying hue. Also it is described the way to select the proper file format with those four features. In the thumbnail image generation experiments, 6 sample images are used, and with subjective assessment experiments, the resulted thumbnail images are shown to be consistent to the file formats chosen by human subjects, that is, favorable to human vision, which means the proposed method can be utilized as an automatic and systematic generation of thumbnail images for a lot of images on Web.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.2
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• pp.359-367
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• 2016

As taking pictures by using smartphones has become more common in society, there are many incidents which are unexpected manipulation of images and leak of confidential information. Because of those incidents, demands that identify forgery/alteration of image file and proves of the original copy is constantly increasing. In general, smartphone saves image file as JPEG form and it has DQT which determines a compression rate of image in a header part of image. There is also DQT in Thumbnail image which inside of JPEG. In previous research, it identified a smartphone which take image by only using DQT, However, the research has low accuracy to identify the devices. There are two main purposes in this research. First, this research will analogize a smartphone and an application that takes a picture, edits and save an image file by testing not only about a DQT information but also a information of Thumbnail image. Second, the research will build a database of DQT and Thumbnail information in JPEG file to find more accurate image file's origin.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.23-32
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• 2011

In this paper, we develop a method for generating thumbnail images at hybrid domain combined the spatial domain and transform domain. The proposed method generates a pixel of a thumbnail image by adding a DC value of residual transform coefficients and an average value of an estimate block. For effectively calculating average values of estimate blocks, we propose a method for reconstructing the boundary pixels of a block. In comparison to the conventional method of decoding the bit stream then scaling down the decoded images, the developed method reduces the complexity by more than 60% while producing identical thumbnail images.

• Journal of Broadcast Engineering
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• v.23 no.3
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• pp.431-436
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• 2018

In this paper, a simple but effective algorithm to reduce the computational complexity of thumbnail generation and to improve image quality without aliasing artifacts is proposed. For the high speed decoding, the proposed algorithm performs partial decoding per $4{\times}4$ boundary in TU(Transform Unit), and preforms TU boundary in PU(Prediction Unit). The proposed method defines the weights based on intra prediction directions and estimates the thumbnail pixel by using that weights. this method remains thumbnail extraction time and improves thumbnail image quality compared with conventional algorithms.

• Journal of Broadcast Engineering
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• v.12 no.5
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• pp.525-534
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• 2007

H.264/AVC for DMB is the most advanced video compression standard which provides a high compression rate and a video quality by adopting new technologies. However, these new technologies prevent us from applying some conventional algorithms directly to the H.264/AVC compression domain. For example, we need to study new image resizing schemes in the compressed bit-stream. So, in this paper, we propose a new thumbnail extraction method which can be applied to H.264. The proposed method shows that it can extract a 1/16 size thumbnail video, saving the operation time up to 50% to 70%.

• Journal of Broadcast Engineering
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• v.13 no.2
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• pp.222-235
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• 2008

Recently, as growing of high definition media services like HDTV and IPTV, fast moving picture manipulation techniques need to meet what those services require. Especially, a fast reduced-size image extracting method is required in the areas of video indexing and video summary Conventional DC image extracting methods, however, can't be applied to H.264/AVC streams since a spatial domain prediction scheme is adopted in H.264/AVC intra mode. In this paper, we propose a theoretical method for extracting a thumbnail image from an H.264/AVC intra frame in the frequency domain. Furthermore, the proposed scheme can extract the thumbnail very fast since all operations are applied to transform coefficients directly, after a general equation for the thumbnail extraction in nine H.264/AVC intra prediction modes is introduced, an LUT(Look Up Table) for each mode is designed. Through the implementation and performance evaluation, while the subject quality difference between the output of our scheme and a conventional output is negligible, the former can extract the thumbnail faster then the latter by up to 63%.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.622-635
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• 2008

Recently, high definition media services like HDTV and IPTV are growing. A fast reduced-size image extracting method is required to meet what those services require. Conventional DC image extracting methods, however, can't be applied to H.264/AVC streams since a spatial domain prediction scheme is adopted in H.264/AVC intra mode. To solve this problem, a thumbnail extraction method in H.264/AVC was proposed. However, the method has mismatch problem which was caused by round-off operation in intra prediction and mismatch between integer and floating point calculation. In this paper, we propose an error compensation method for extracting thumbnail directly in H.264/AVC bitstreams. The compensation method introduces the mismatch problem in thumbnail extraction and presents compensation values. Through the implementation and performance evaluation, proposed method compensated round-off error efficiently in D1 and HD sequences while the additional extraction time is negligible.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.3
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• pp.10-17
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• 2009

This paper proposes a compressed domain signature extraction method which can be used for CBCD (Content Based Copy Detection). Since existing signature extraction methods for the CBCD are executed in spatial domain, they need additional computations to decode the compressed video before the signature extraction. To avoid this overhead, we generate a thumbnail image directly from the compressed video without full decoding. Then we can extract the video signature from the thumbnail image. Experimental results of extracting brightness ordering information as the signature for CBCD show that our proposed method is 2.8 times faster than the spatial domain method while maintaining 80.98% accuracy.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.413-421
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• 2005

As the population of HDTV is growing, among many useful features of modern set top boxes (STBs) or digital video recorders (DVRs), video browsing, visual bookmark, and picture-in-picture capabilities are very frequently required. These features typically employ reduced-size versions of video frames, or thumbnail images. Most thumbnail generation approaches generate DC images directly from a compressed video stream. A discrete cosine transform (DCT) coefficient for which the frequency is zero in both dimensions in a compressed block is called a DC coefficient and is simply used to construct a DC image. If a block has been encoded with field DCT, a few AC coefficients are needed to generate the DC image in addition to a DC coefficient. However, the bit length of a codeword coded with variable length coding (VLC) cannot be determined until the previous VLC codeword has been decoded, thus it is required that all codewords should be fully decoded regardless of their necessary for DC image generation. In this paper, we propose a method especially for fast DC image generation from an I-frame using multiple-symbol lookup table (mLUT). The experimental results show that the method using the mLUT improves the performance greatly by reducing LUT count by 50$\%$.

• 한국HCI학회:학술대회논문집
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• 2008.02b
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• pp.298-303
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• 2008

Watching a program on IPTV among the numerous choices from the internet requires a burden of searching and browsing for a favorite one. This paper introduces a new concept called Mosaic Map and presents how it provides preview information of image map links to other programs. In Mosaic Map the pixels in the still image are used both as shading the background and as thumbnails which can link up with other programs. This kind of contextualized preview of choices can help IPTV users to associate the image with related programs without making visual saccades between watching IPTV and browsing many choices. The experiments showed that the Mosaic Map reduces the time to complete search and browsing, comparing to the legacy menu and web search.