Abstract:
This paper considers the design of a lossy image
compression algorithm dedicated to color still images. After a
preprocessing step (mean removing and
RGB to YCbCr transformation), the
DCT transform is applied and followed by an iterative phase (using the bisection method) including the thresholding, the
quantization, dequantization, the inverse DCT, YCbCr to RGB transform and the mean recovering. This is done in order to guarantee that a desired quality (fixed in advance using the well known
PSNR metric) is checked. For the aim to obtain the best possible
compression ratio CR, the next step is the application of a proposed adaptive scanning providing, for each (
n,
n) DCT block a corresponding (
n×
n) vector containing the maximum possible run of zeros at its end. The last step is the application of a modified systematic lossless
encoder. The efficiency of the proposed scheme is demonstrated by results, especially, when faced to the method presented in the recently published paper based on the
block truncation coding using pattern fitting principle.
Publisher's Version