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Using Computer Using Computer Vision to Test Web Vision to Test Web DisplayDisplayXu LiuXu Liu
[email protected]@cs.umd.edu
Where comes these Where comes these bugs?bugs?
Different parsers on DHTML, CSSDifferent parsers on DHTML, CSS Web designer doesn’t follow W3C Web designer doesn’t follow W3C
standardstandard IE tolerant buggy HTMLIE tolerant buggy HTML Java Script, ActiveX, FlashJava Script, ActiveX, Flash
Which kinds of bugs do Which kinds of bugs do we have? we have?
Text/Image OverlapText/Image Overlap Incorrect blank areaIncorrect blank area Missing Text/ImageMissing Text/Image
Generally they are all layout problems
How do we detect these How do we detect these bugsbugs
Is HTML source helpful?Is HTML source helpful? Yes, but we need a correct parser which is Yes, but we need a correct parser which is
being testedbeing tested
HTML does not have straight forward HTML does not have straight forward relationship with displayrelationship with display
Eyes always tell the truth – directly use Eyes always tell the truth – directly use the image of snapshotthe image of snapshot
Find the outlierFind the outlier
Let them vote:Let them vote: IE, Firefox, Mozilla, Netscapte, Opera, MyIEIE, Firefox, Mozilla, Netscapte, Opera, MyIE
…… Anyone seems distinct from others is probabAnyone seems distinct from others is probab
ly an outlierly an outlier Assumption : Major are correct, Minor are inAssumption : Major are correct, Minor are in
correctcorrect
Basic QuestionBasic Question
How do we compare 2 images? Are they same?How do we compare 2 images? Are they same?Missing
Front and end
These 2 look different but they should be considered the same
Simpler QuestionSimpler Question
How do we compare 2 sequences? How do we compare 2 sequences?
S1: 1 2 3 4 5 6 8 7
S2: 1 2 4 5 5 5 6 7
Direct Compare
|S1-S2|=0+0+1+1+0+1+2+0=5
Dynamic Time Warping !!
In fact ||S1-S2||=0,
they should be considered the same
Dynamic Time Warping Dynamic Time Warping (DTW)(DTW)
A widely used technique in signal processing A widely used technique in signal processing Speech recognition, Image matchingSpeech recognition, Image matching
Compare S1,S2
1 2
(0,0) 0
( , ) min { ( , 1) | 1( ) 2( ) |}
| 1 2 | ( 1. (), 2. ())i k i
Diff
Diff i j Diff k j S i S j
S S Diff S length S length
Can we directly apply Can we directly apply DTW to compare web DTW to compare web pages?pages?
No!No!
Segmentation First!!
If we directly compare 2 pages:
Most of the error will be omitted
Local VS Global
How do we derive How do we derive segmentationssegmentations
Edge Detection FirstEdge Detection First
Over SegmentOver SegmentMergeMerge
NextNext
For every pageFor every page We have all its segmentsWe have all its segments
For every segmentFor every segment If it CANNOT be found in other pages, If it CANNOT be found in other pages,
possibly it is an errorpossibly it is an error