A Database of Human Segmented Natural Images and Two Applications David Martin, Charless Fowlkes, Doron Tal, Jitendra Malik UC Berkeley
David Martin - UC Berkeley - ICCV Motivation Berkeley Segmentation Dataset Groundtruth for image segmentation of natural images App#1: A segmentation benchmark App#2: Ecological statistics
David Martin - UC Berkeley - ICCV Benchmark Example for Recognition MNIST handwritten digit dataset [LeCun, AT&T] Training set, test set, evaluation methodology, algorithm ranking
David Martin - UC Berkeley - ICCV The Image Dataset 1000 Corel images –Photographs of outdoor scenes –Texture is common –Large variety of subject matter –481 x 321 x 24b
David Martin - UC Berkeley - ICCV 20015
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9 Establishing Groundtruth Def: Segmentation = Partition of image pixels into exclusive sets Manual segmentation by human subjects –Custom Java tool to facilitate task Currently: 1000 images, 5500 segmentations, 20 subjects Naïve subjects (UCB undergrads) given simple, non-technical instructions
David Martin - UC Berkeley - ICCV Directions to Image Segmentors You will be presented a photographic image Divide the image into some number of segments, where the segments represent “things” or “parts of things” in the scene The number of segments is up to you, as it depends on the image. Something between 2 and 30 is likely to be appropriate. It is important that all of the segments have approximately equal importance.
David Martin - UC Berkeley - ICCV
David Martin - UC Berkeley - ICCV
David Martin - UC Berkeley - ICCV The segmentations are not identical. But are they consistent??
David Martin - UC Berkeley - ICCV Perceptual organization forms a hierarchy image backgroundleft birdright bird grassbush headeye beakfar body headeye beak body Each subject picks a slice through this hierarchy.
David Martin - UC Berkeley - ICCV Quantifying inconsistency S1S1 S2S2 How much is S 1 a refinement of S 2 at pixel ?
David Martin - UC Berkeley - ICCV Segmentation Error Measure One-way Local Refinement Error: Segmentation Error allows refinement in either direction at each pixel:
David Martin - UC Berkeley - ICCV Human segmentations are consistent Distribution of segmentation error over the dataset.
David Martin - UC Berkeley - ICCV ColorGrayInvNeg
David Martin - UC Berkeley - ICCV InvNeg
David Martin - UC Berkeley - ICCV ColorGrayInvNeg
David Martin - UC Berkeley - ICCV Gray vs. Color vs. InvNeg Segmentations SE (gray, gray) = SE (gray, color) = Color may affect attention, but doesn’t seem to affect perceptual organization SE (gray, gray) = SE (gray, invneg) = InvNeg interferes with high-level cues (2500 gray, 2500 color,200 invneg segmentations)
David Martin - UC Berkeley - ICCV Benchmark Methodology Separate training and test datasets with no images in common Generate computer segmentation(s) of each image in test set –Determine error of each computer segmentation using SE measure –Algorithm scored by mean SE Example: –SE (human, human) = 0.05 –SE (NCuts, human) = 0.22 –SE (different images) = 0.30
David Martin - UC Berkeley - ICCV Ecological Statistics of Image Segmentations Validating and quantifying Gestalt grouping factors [Brunswik 1953] Priors on region properties Recent work on natural image statistics: –Filter outputs [Ruderman 1994, Olshausen & Field 1996, Yuille et. al. 1999] –Object sizes [Alvarez, Gousseau, Morel 1999] –Shape [Zhu 1999] –Contours [August & Zucker 2000, Geisler et al. 2001]
David Martin - UC Berkeley - ICCV Relative power of cues Pairwise grouping cues –Proximity –Luminance similarity –Color similarity –Intervening contour –Texture similarity
David Martin - UC Berkeley - ICCV P (Same Segment | Proximity)
David Martin - UC Berkeley - ICCV P (Same Segment | Luminance)
David Martin - UC Berkeley - ICCV Bayes Risk for Proximity Cue
David Martin - UC Berkeley - ICCV Bayes Risk for Various Cues Conditioned on Proximity
David Martin - UC Berkeley - ICCV Mutual Information for Various Cues Conditioned on Proximity
David Martin - UC Berkeley - ICCV Priors on Region Properties Area Convexity
David Martin - UC Berkeley - ICCV Empirical Distribution of Region Area y = Kx - = Compare with Alvarez, Gousseau, Morel 1999.
David Martin - UC Berkeley - ICCV Empirical Distribution of Region Convexity
David Martin - UC Berkeley - ICCV Conclusion Large new database of segmentations of natural images by humans A segmentation benchmark Ecological statistics –Relative power of grouping cues –Priors on region properties