In this paper, we present a novel hybrid image coding scheme for real-time applications of computer screen video transmission. based on the Mixed Raster Content (MRC) multilayer imaging model, the background picture i...
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ISBN:
(纸本)0819452114
In this paper, we present a novel hybrid image coding scheme for real-time applications of computer screen video transmission. based on the Mixed Raster Content (MRC) multilayer imaging model, the background picture is compressed with lossy JPEG, and the foreground layer consisting of text and graphics is compressed with a block-based lossless coding algorithm, which integrates shape-basedcoding, palette-based coding, palette reuse, and LZW algorithm. The key technique is to extract text and graphics from background pictures accurately and with low complexity. Shape primitives, such as lines, rectangles, and isolated pixels with prominent colors, are found to be significant clues for textual and graphical contents. The shape-basedcoding in our lossless algorithm provides intelligence to extract the computer-generated text and graphics elegantly and easily. Experimental results demonstrate the efficiency and low complexity of our proposed hybrid image coding scheme.
We present a compound image compression algorithm for real-time applications of computer screen image transmission. It is called shape primitive extraction and coding (SPEC). Real-time image transmission requires that...
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We present a compound image compression algorithm for real-time applications of computer screen image transmission. It is called shape primitive extraction and coding (SPEC). Real-time image transmission requires that the compression algorithm should not only achieve high compression ratio, but also have low complexity and provide excellent visual quality. SPEC first segments a compound image into text/graphics pixels and pictorial pixels, and then compresses the text/graphics pixels with a new lossless coding algorithm and the pictorial pixels with the standard lossy JPEG, respectively. The segmentation first classifies image blocks into picture and text/graphics blocks by thresholding the number of colors of each block, then extracts shape primitives of text/graphics from picture blocks. Dynamic color palette that tracks recent text/graphics colors is used to separate small shape primitives of text/graphics from pictorial pixels. Shape primitives are also extracted from text/graphics blocks. All shape primitives from both block types are losslessly compressed by using a combined shape-based and palette-based coding algorithm. Then, the losslessly coded bitstream is fed into a LZW coder. Experimental results show that the SPEC has very low complexity and provides visually lossless quality while keeping competitive compression ratios.
Non-camera captured images (also known as compound image) contain a mixture of camera-captured natural images and computer-generated graphics and texts. Nowadays, there are more and more applications calling for non-c...
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ISBN:
(纸本)9781479928934
Non-camera captured images (also known as compound image) contain a mixture of camera-captured natural images and computer-generated graphics and texts. Nowadays, there are more and more applications calling for non-camera captured image/video compression scheme. However, current video coding standards, which are designed for natural video, treat non-camera captured video less carefully. For example, the state-of-the-art video coding standard High Effciency Video coding (HEVC) may blur or even remove edges in text/graphic region. A lot of schemes are proposed to preserve direction property of texts and graphics, such as palette-based intra coding. In this paper, a novel palettecoding scheme is proposed for palette-based intra coding in HEVC. The palette in a block is predicted from an adaptive palette template, which records the statistical non-local spatial correlation of an image. Every block chooses its own palette using the palette template as the prediction in a rate-distortion optimized manner. Experimental results show that the proposed scheme can achieve up to 5.2% bit-rate saving compared to the state-of-the-art palette-based coding scheme in HEVC.
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