MATCHSLIDE : INT contribution Patrick HORAIN Hichem ATTI Waheb LARBI Presented as : "TELESLIDE: Technical aspects ", Jacques Klossa & Patrick Horain, Joint Congress of Quantitative Analytical Cellular Pathology ans Telepathology, September , Heraclion, Crete.

2 Wide fields : some issues Acquisition :  A microscope can see only a small field in a slide Browsing wide fields :  Narrow band networks  Narrow computer screens

Wide field acquisition

4 1 image, 4662  3675 pixels Mosaicing  Grab neighbour fields images and merge (mosaic) them into a wide field image Ex.: 16 images, 1300  1030 pixels

5 Shading : what ? Problems : –Illumination inhomogeneities –Dust in optical system Example empty slide : original stretched histogram

6 Shading correction / single field  Normalise each pixel with illumination /=

7 Without shading correction With shading correction Shading correction / wide field

8 Other issues Future work includes : –color correction –robust slides registration for mosaicing –hierarchical RoI definition by image analysis

Wide field browsing

10 Browsing requirements  Narrow band networks  Use better compression  Use progressive transmission  Use regions of interest  Narrow computer screens  Use interactive windowing while loading  Use the new JPEG 2000 standard

11 What is JPEG 2000 ? New ISO Image compression Standard –Wavelet-based –Lossless or lossy compression –Better low bit-rate performance than JPEG –Progressive transmission by pixel accuracy and resolution –Random code stream access and processing  Interactive zooming and regions of interest

12 JPEG 2000 : wavelets Discrete wavelets transform (DWT)  recursive image decomposition into frequency subbands

13 JPEG 2000 versus JPEG DWT integrates a spatial and frequency representation of images without the blocks effect of DCT. At low bit rates, less image degradation with JPEG 2000 than with JPEG. Original (24 bpp) JPEG (0.18 bpp)JPEG2000 (0.099 bpp)

14 Progressive transmission : resolution levels Resolution 2 : 163  129 pixels (1.61 % of data) Resolution 5 : 1300  1030 pixels (100 % of image data) Resolution 1 : 82  65 pixels (0.45% data) Resolution 4 : 650  515 pixels (25 % of image data) Resolution 3 : 325  258 pixels (6.25% of image data)

15 1 rst layer : 12 kb (7.36 % of image data) Progressive transmission : quality layers Progression on the precision of the DWT coefficients 5 th layer : 14.9 kb (9.14 % of image data) 10 th layer : 18.1 kb (11.1 % of image data) 20 th layer : 163 kb (100 % of image data) 15 th layer : 27 kb (16.6 % of image data)

16 Progressive transmission : other modes Progression modes : –R : Resolution (DWT levels) –L : Quality Layers –C : Components –P: Position 5 std progression orders (apply from right to left) : –LRCP, RLCP, RPCL, PCRL, CPRL

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18 Regions of interest (RoI) RoI can be coded with different fidelity –ex.: lossless RoI vs. lossy background RoI = a rectangle or an arbitrary mask RoI data transmitted before background

19 RoI as a rectangle

20 RoI as an arbitrary mask

bpp0.399 bpp Progressive transmission with RoI

22 Other issues Future work includes : –comparative evaluation of the progression modes w. r. to our target application –automatic RoI selection by image analysis –compression and interaction on multiple focus images