Image Encoding Apparatus Adaptive Prediction for Vertical Stripes
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Solution Overview
Problem
Existing image compression methods fail to achieve a high compression ratio efficiently when dealing with images that have low horizontal correlation and high vertical correlation, such as images with vertical stripes, due to the need for additional processing and increased computational resources.
Innovation Solution
An image encoding apparatus that calculates predicted pixel values using both neighboring pixels and pixels separated by a predetermined period, with a correlation calculation unit determining the best prediction method based on correlation values, and an encoding unit encoding the pixel values accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dither matrix is applied for color reduction, then quantization to fewer gray levels is achieved, but neighboring pixel correlation deteriorates and compression ratio decreases
Solution Approach 1:
The patent segments the prediction process into two distinct modes: intra-block prediction using neighboring pixels within the same block, and inter-block prediction using pixels from other blocks. This segmentation allows the system to adaptively select the appropriate prediction method based on local image characteristics, preserving correlation information that would otherwise be lost due to dither matrix application.
Solution Approach 2:
The patent introduces dynamic adaptation by calculating correlation values between neighboring pixels and pixels separated by block boundaries, then selectively switching between intra-block and inter-block prediction methods. This dynamic approach enables the encoding system to respond to local image features, maintaining high compression ratios even after dither-based quantization.
2Loss of information
If interlaced process is used to improve vertical correlation, then pixels having high correlation align, but additional rearrangement process increases encoding time
Solution Approach 1:
The patent performs preliminary organization of pixel data into blocks during the encoding process, establishing block boundaries that facilitate efficient inter-block prediction. By pre-structuring the data in block form, the system enables direct access to pixels separated by block boundaries without requiring additional rearrangement steps, thus improving vertical correlation while avoiding increased encoding time.
3Ease of manufacture
If pixels are referred to without rearrangement, then encoding process is simplified, but vertical correlation cannot be utilized for compression
Solution Approach 1:
The patent implements a dynamic prediction mechanism that adaptively selects between intra-block prediction (using only neighboring pixels within the same block) and inter-block prediction (using pixels from other blocks). By calculating correlation values and selectively switching prediction modes, the system utilizes vertical correlation information without requiring physical rearrangement of pixel data, thus maintaining encoding simplicity while improving compression efficiency.
4Loss of information
If prediction encoding is applied to dithered image, then compression is achieved, but calculation volume and encoding time increase significantly
Solution Approach 1:
The patent segments the prediction process into two distinct modes with different computational characteristics: intra-block prediction that uses only locally available neighboring pixels (low computation), and inter-block prediction that uses pixels from other blocks (higher computation but better compression for certain patterns). This segmentation allows the encoder to choose the appropriate level of computational effort based on local image characteristics.
Solution Approach 2:
The patent implements partial action by selectively applying inter-block prediction only when correlation values indicate it will be beneficial. The system calculates correlation metrics and applies the more computationally intensive inter-block prediction method only in regions where it will significantly improve compression, while using simpler intra-block prediction elsewhere, thus balancing compression ratio improvement against computational cost.
Data Source
AI summary
This invention can generate encoded data of a high compression ratio of not only a halftone image but also a vertical stripe portion or text portion, which is weak in the conventional method, by a simple process or circuit scale, and can decode the encoded data on the decoding side by a simple process or circuit scale. To this end, image data is input from an input terminal (109). A reference pixel value storage unit (101) stores image data for one period of a dither matrix. A first prediction unit (102) calculates a predicted value of a pixel of interest with reference to threshold values less than one period of pixel values, which are stored in the reference pixel value storage unit (101). A second prediction unit (104) determines a pixel value one period before the pixel of interest as a predicted value. A continuity checking unit (105) compares first to third pixel values before the pixel of interest with three pixel values one period before the dither matrix, checks whether or not the number of matches is larger than the number of mismatches, and outputs the result to a predicted value selection unit (106). The predicted value selection unit selects one predicted value according to the checking result, and an encoding unit (107) encodes a difference between the selected predicted value and the pixel of interest.