In this study a color image compression scheme was introduced, the proposed scheme was applied to images in RGB and YCbCr color models for the issues of comparison in performance; each plane was partitioned into 16x16 blocks and 1-D DCT was used to transform the image planes to frequency domain instead of 2-D DCT (typically applied to images) for the purpose of compression/ decompression time reduction; the implementation time was reduced by 47:1 for the DCT step only. An adaptive scalar quantization step is applied on all image planes in RGB color model, but for YCbCr color model the quantization parameters where reduced by half for the chrominance plane while it is the same for the luminance planes to preserve the image quality, the zigzag scan was used to rearrange the data from non-zero low frequency coefficients to high frequency coefficients, where the adaptive shift coding was applied that performs Differential Pulse Coding Modulation on the DC coefficients for the entire image and Run Length Encoding for the AC coefficients for the entire image; the shift optimizer was applied to these coefficients to produce the exact number of bits needed to represent each one of them . The attained compression results indicated good efficiency in terms of compression gain while keeping the fidelity level above the acceptable level.
展开▼
