wavelet based color compression

WAVELET BASED COLOR COMPRESSIONGreg Beranek

BACKGROUND WDR

Significance Pass With threshold T and T2 find item where T2>Item>=T

Encode the Address Encode Plus or Minus

Repeat Refinement Pass

If Item >=T2 Write Refinement

Repeat

WDR

COLOR WDR Significance Pass

Three Passes Red Pass Green Pass Blue Pass

Refinement Three Passes

Red Green Blue

COLOR WDR

ISSUES COLOR WDR Progressive nature

Cannot stop anywhere (missing color component)

Speed 3 Passes 3 Scan orders 3 data matrices

Accounting

RESOLUTION TO COLOR WDR ISSUES Color Correlation (lack of correlation)

Ability to predict significant values Encode more data with one color and get a very

close color when decoding Simplify scan order

COLOR SPACE Primitive Color Spaces

RGB Additive color space Tells how much light is needed to make a specific color

CYM K Subtractive color space Tell what quantity of pigment is needed to make a

specific color Other Color Spaces

YUV YPbPr (YCbCr)

Video and Image Compression Schemes, Analog (Digital)

YCoCg Integer to Integer Color space similar to YPbPr

TRANSFORM MATRIX RGB TO YCOCG Forward - RGB -> YCoCg

Reverse - YCoCg -> RGB

BACK TO COLOR WDR We now have the ability to:

Predict significant color values

Simplify to one scan order

Retain some RGB color information when we stop encoding anywhere

COLOR WDR

OPTIMIZATIONS

Encoder optimizations

ASWDR

Lossy Color Space

HOW GOOD IS THIS COMPARED TO JPEG 2000?

PSNR from Color Compression of Lena

1bpp (24:1) 0.5bpp (48:1)

JPEG2000 34.320604 32.239947

Color WDR 33.414003 31.180589

PSNR from Color Compression of Parrots (kodim23)

1bpp (24:1) 0.5bpp (48:1)

JPEG2000 40.553139 37.526301

Color WDR 38.60774 34.599361

PSNR from Color Compression of Hats (kodim03)

1bpp (24:1) 0.5bpp (48:1)

JPEG2000 39.946701 35.951137

Color WDR 34.542265 32.215072

PICTURES LENA

Left : Original (Cropped)Top Right : Color WDR 1 bppBottom Right : JPEG 2000 1 bpp

PICTURES HATS

Left : Original (Cropped)Top Right : Color WDR 1 bppBottom Right : JPEG 2000 1 bpp

PICTURES PARROTS

Left : Original (Cropped)Top Right : Color WDR 1 bppBottom Right : JPEG 2000 1 bpp

QUESTIONS?