A Jpeg Corner Artifact from Directed Rounding of Dct Coefficients
نویسندگان
چکیده
JPEG compression introduces a number of well known artifacts including blocking and ringing. We describe a lesser known or understood artifact consisting of a slightly darker or lighter pixel in the corner of 8×8 pixel blocks. This artifact is introduced by the directed rounding of DCT coefficients. In particular, we show that DCT coefficients that are uniformly rounded down or up (but not to the nearest neighbor) give rise to this artifact. An analysis of thousands of different camera models reveals that this artifact is present in approximately 61% of cameras. We also propose a simple filtering technique for removing this artifact.
منابع مشابه
A robust image authentication method distinguishing JPEG compression from malicious manipulation
Image authentication verifies the originality of an image by detecting malicious manipulations. Its goal is different from that of image watermarking, which embeds into the image a signature surviving most manipulations. Most existing methods for image authentication treat all types of manipulation equally (i.e., as unacceptable). However, some practical applications demand techniques that can ...
متن کاملReduction of Blocking Artifacts In JPEG Compressed Image
In JPEG (DCT based) compresses image data by representing the original image with a small number of transform coefficients. It exploits the fact that for typical images a large amount of signal energy is concentrated in a small number of coefficients. The goal of DCT transform coding is to minimize the number of retained transform coefficients while keeping distortion at an acceptable level.In ...
متن کاملLossless, near-lossless and lossy adaptive coding based on the lossless DCT
This report proposes a new coding method, which realizes lossless, near-lossless and lossy coding with a unified single algorithm. The method is based on a lifting-structured lossless DCT, which maps an "integer" input vector to also an "integer" output vector. The proposed method can be used as not only a high performance "lossless" encoder but also a "lossy" encoder compatible to conventional...
متن کاملPerceptible Content Retrieval in DCT Domain and Semi-Fragile Watermarking Technique for Perceptible Content Authentication
Digital watermarking was commenced to copyright protection and ownership verification of multimedia data. However the evolution of the watermark focused on different security aspects of multimedia data such as integrity and authenticity. Fragile and semi-fragile watermarking schemes were introduced to accomplish these requirements. In this paper, we propose semi-fragile watermarking scheme to a...
متن کاملCosine Transform Priors for Enhanced Decoding of Compressed Images
Abstract. Image compression methods such as JPEG use quantisation of discrete cosine transform (DCT) coefficients of image blocks to produce lossy compression. During decoding, an inverse DCT of the quantised values is used to obtain the lossy image. These methods suffer from blocky effects from the region boundaries, and can produce poor representations of regions containing sharp edges. Such ...
متن کامل