1. JCDL 2005 – June 8 th, 2005 User Perceptions of Digital Image Similarity Unmil Karadkar, Richard Furuta, Jeevan Joseph John Center for the Study of Digital Libraries Texas A&M University Jin-Cheon Na Division of Information Studies Nanyang Technological University

2. JCDL 2005 – June 8 th, 2005 Outline Motivation Study –Research questions –Setting and Design –Analysis of results Significance –Theoretical –Practical

3. JCDL 2005 – June 8 th, 2005 MIDAS (Multi-device Integrated Dynamic Activity Spaces) M ulti-device I ntegrated D ynamic A ctivity S paces World- Wide Web PERCEPTIONPERCEPTION

4. JCDL 2005 – June 8 th, 2005 Context of Information Space Images –Graphs (visual data representations) –Line drawings (cartoons, comic strips) –Art (sketches, paintings) –Photographs (scanned or digital) Quick growth –Digital cameras –Camera phones Text Audio Video Animation

5. JCDL 2005 – June 8 th, 2005 Research Question How does the variation of image attributes affect user perception of images? Variables: Size (scaling) Colors (change of color depth) –How does the perception of similarity change? –Do users allow automatic substitution of modified images for best display on a device? –How does variation affect the confidence of image substitution?

6. JCDL 2005 – June 8 th, 2005 Image Characteristics Size (pixels) –160x120 (smart phone) –320x240 (PDA) –640x480 (CSISD schools) –800x600 (notebooks) –1024x768 (desktop computers) Colors –2 (b/w) (1-bit) –4 (2-bit) –16 (4-bit) –256 (8-bit) –16 Million (24-bit) Image types – People– Nature – Structures– Text 4 images of each type

7. JCDL 2005 – June 8 th, 2005 Subject Pool Characteristics 5 Users Graduate students and staff Male and female Different academic backgrounds –Engineering, sciences, architecture Different nationalities and cultures Mid-twenties to early forties

8. JCDL 2005 – June 8 th, 2005 Setting of the Study Computer with 2 identical displays One image on each display Time not a factor Users could take a break Users could clarify doubts and ask questions Evaluator did not interrupt the users during the task

9. JCDL 2005 – June 8 th, 2005 Design of Study Users viewed pairs of images 3 questions per pair –Perceived level of similarity (9 pt. Likert scale) –Would they allow substitution of one image for another (9 pt. Likert scale) –Automatic substitution acceptable (Yes/No) No confounding effects –Each pair differed in size or colors but not both 20 pairs for each variable

10. JCDL 2005 – June 8 th, 2005 Results – Perception of Similarity Scales for size and color are not comparable StepsWithin color Color to grayscale 0-6.89 16.695.57 24.64.55 35.864.00 44.14- StepsSimilarity 0- 17.12 27.11 36.87 46.14 SizeColor

11. JCDL 2005 – June 8 th, 2005 Results – Similarity by image type People’s faces Legibility of textual elements Nature and structural images scale well Stepsnaturepeoplestructurestext 16.577.177.676.78 27.337.096.787.25 37.757.00 6.29 47.005.717.505.00 Size

12. JCDL 2005 – June 8 th, 2005 Results – Image Substitution Automatic substitution –High confidence but fewer instances Substitution with warning –More instances but confidence dropped StepsAutomatic substitution ConfidenceSubstitution with warning Confidence 144%7.6656%6.05 249%7.4251%6.00 350%7.1350%6.50 421%7.4779%4.18 Size

13. JCDL 2005 – June 8 th, 2005 Significance of Results Theoretical –Provides an insight into human image perception –Nature and structural images scale well –Images of people and text scale to a lesser degree Practical –Design guidelines for image optimization Scale images rather than reducing colors –Use other techniques, such as cropping for better scaling of textual and people images

14. JCDL 2005 – June 8 th, 2005 Questions?