Wavelet Based Color Compression - PowerPoint PPT Presentation

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Wavelet Based Color Compression

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Integer to Integer Color space similar to YPbPr. TRANSFORM MATRIX RGB TO YCOCG ... Predict significant color values. Simplify to one scan order ... – PowerPoint PPT presentation

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Title: Wavelet Based Color Compression


1
Wavelet Based Color Compression
  • Greg Beranek

2
Background
  • WDR
  • Significance Pass
  • With threshold T and T2 find item where
    T2gtItemgtT
  • Encode the Address
  • Encode Plus or Minus
  • Repeat
  • Refinement Pass
  • If Item gtT2
  • Write Refinement
  • Repeat

3
WDR
4
Color WDR
  • Significance Pass
  • Three Passes
  • Red Pass
  • Green Pass
  • Blue Pass
  • Refinement
  • Three Passes
  • Red
  • Green
  • Blue

5
Color WDR
6
Issues Color WDR
  • Progressive nature
  • Cannot stop anywhere (missing color component)
  • Speed
  • 3 Passes
  • 3 Scan orders
  • 3 data matrices
  • Accounting

7
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

8
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

9
Transform Matrix RGB to YCoCg
  • Forward - RGB -gt YCoCg
  • Reverse - YCoCg -gt RGB

10
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

11
Color WDR
12
Optimizations
  • Encoder optimizations
  • ASWDR
  • Lossy Color Space

13
How good is this compared to JPEG 2000?
PSNR from Color Compression of Lena PSNR from Color Compression of Lena PSNR from Color Compression of Lena
  1bpp (241) 0.5bpp (481)
JPEG2000 34.320604 32.239947
Color WDR 33.414003 31.180589
     
PSNR from Color Compression of Parrots (kodim23) PSNR from Color Compression of Parrots (kodim23) PSNR from Color Compression of Parrots (kodim23)
  1bpp (241) 0.5bpp (481)
JPEG2000 40.553139 37.526301
Color WDR 38.60774 34.599361
     
PSNR from Color Compression of Hats (kodim03) PSNR from Color Compression of Hats (kodim03) PSNR from Color Compression of Hats (kodim03)
  1bpp (241) 0.5bpp (481)
JPEG2000 39.946701 35.951137
Color WDR 34.542265 32.215072
14
Pictures Lena
Left Original (Cropped) Top Right
Color WDR 1 bpp Bottom Right JPEG 2000
1 bpp
15
Pictures Hats
Left Original (Cropped) Top Right
Color WDR 1 bpp Bottom Right JPEG 2000
1 bpp
16
Pictures Parrots
Left Original (Cropped) Top Right
Color WDR 1 bpp Bottom Right JPEG 2000
1 bpp
17
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