a new pca-based compression method for natural color images arash abadpour dr. shohreh kasaei...
Post on 21-Dec-2015
215 views
TRANSCRIPT
A New PCA-based Compression Method for Natural Color Images
Arash Abadpour Dr. Shohreh Kasaei
Mathematics Science Department
Computer Engineering Department
Sharif University of Technology, Tehran, Iran
Outline Introduction
Colorizing, Quad-Tree Decomposition, Color Space Dimension Reduction.
Method Homogeneity Criteria, Quad-Tree Decomposition,
Bi-Tree Decomposition, Color Image Compression, Decompression.
Experimental Results Block Count Growth, Block Count, Samples, Peak
Signal to Noise Ratio, Compression Ratio, Elapsed Time.
Colorizing Many Modern Systems Produce Gray-
Scale Images: MRI, CT-SCAN, Infrared, …
Color Images are More Preferred: Larger Amount of Information.
Conversion: Color to Grayscale: Trivial. Grayscale to Color: Complicated, Needs
User Intervention.
Colorizing (Cntd.) Literature Review:
Pseudocoloring: Not Realistic.
A Few Other Reports. We Proposed
Elsewhere: PCA-Based
Colorizing: Have you ever seen
Barabara in Color? Faster, Subjectively
Better.
Quad-Tree Decomposition
Splitting an Image into Homogenous Blocks. Recursively. Until Enough Homogenous or Too Small.
To Avoid Over-Segmentation.
Generalized Quad-Tree: Shape (e.g. Triangle), Dimension
(Hypercube)
Quad-Tree Decomposition (Cntd.)
Rectangular Block is Preferred. Computationally Inexpensive. No Round-Off Error.
Quad-Tree Produces Too Many Blocks: One-Split-to-Four.
Declining the Performance of Proceeding Operations.
Color Space Dimension Reduction Illumination
Rejection: Used Frequently.
Principal Component Analysis (PCA). A Proper Tool for
Color Image Processing. Spring or
Autumn, this is the problem.
Quad-Tree Decomposition Splitting Decision.
Minimum Size of Block.
Tree Depth: Asked From User. Computed as:
Bi-Tree Decomposition Bi_11-Tree
Deciding Whether to Cut Vertically or Horizontally:
Bi_12-Tree Decision:
Color Image Compression Lowpass filtering.
To Avoid Aliasing. Bi-Tree Decomposition.
Storing the Result:
Sizes: Original Image: After Compression: Compression Ratio:
Sending the image: Block Information Plus the Grayscale Version. The Grayscale Version is 7-bit quantized. The Extra Bit Holds the Block Information.
Decompression
Easy Way: Colorize each block with Corresponding
Color Information. Enhanced Way:
Interpolate the Vectors and then use them. Splitting all blocks to the smallest size. Using Lowpass filtering.
Conclusions
A New Tree Decomposition Method is Proposed that Out-Performs the Conventional Method.
A New Compression Method is Proposed that Reaches to the Theoretical Margins