This volume constitutes the refereed proceedings of the 4th Iberian Conference on Pattern Recognition and Image Analysis, IbPRIA 2009, held in Póvoa de Varzim, Portugal in June 2009.

Invited Talks.- Inference and Learning for Active Sensing, Experimental Design and Control.- Large Scale Online Learning of Image Similarity through Ranking.- Inpainting Ideas for Image Compression.- Computer Vision.- Improving Scene Recognition through Visual Attention.- Smoothed Disparity Maps for Continuous American Sign Language Recognition.- Human Action Recognition Using Optical Flow Accumulated Local Histograms.- Trajectory Modeling Using Mixtures of Vector Fields.- High-Speed Human Detection Using a Multiresolution Cascade of Histograms of Oriented Gradients.- Face-to-Face Social Activity Detection Using Data Collected with a Wearable Device.- Estimating Vehicle Velocity Using Image Profiles on Rectified Images.- Kernel Based Multi-object Tracking Using Gabor Functions Embedded in a Region Covariance Matrix.- Autonomous Configuration of Parameters in Robotic Digital Cameras.- Facial Reconstruction and Alignment Using Photometric Stereo and Surface Fitting.- Facial Feature Extraction and Change Analysis Using Photometric Stereo.- Match Selection in Batch Mosaicing Using Mutual Information.- Space Carving Acceleration Using Uncertainty Measurements.- Mean Shift Parallel Tracking on GPU.- Local Boosted Features for Pedestrian Detection.- Plane Filtering for the Registration of Urban Range Laser Imagery.- Real-Time Motion Detection for a Mobile Observer Using Multiple Kernel Tracking and Belief Propagation.- Robust and Efficient Multipose Face Detection Using Skin Color Segmentation.- Image Analysis and Processing.- Contour Regularity Extraction Based on String Edit Distance.- Cell Division Detection on the Arabidopsis Thaliana Root.- HOG-Based Decision Tree for Facial Expression Classification.- Class Representative Visual Words for Category-Level Object Recognition.- Multi-Scale Image Analysis Applied to Radioastronomical Interferometric Data.- Robust Statistical Estimation Applied to Automatic Lip Segmentation.- Textural Features for Hyperspectral Pixel Classification.- A New Clustering Algorithm for Color Image Segmentation.- A Top-Down Approach for Automatic Dropper Extraction in Catenary Scenes.- A Scale Invariant Interest Point Detector for Discriminative Blob Detection.- Enhancing In-Vitro IVUS Data for Tissue Characterization.- Toward Robust Myocardial Blush Grade Estimation in Contrast Angiography.- Multi-spectral Texture Characterisation for Remote Sensing Image Segmentation.- Texture Measuring by Means of Perceptually-Based Fineness Functions.- High Performance Circle Detection through a GPU Rasterization Approach.- Appearance and Shape Prior Alignments in Level Set Segmentation.- The Diagonal Split: A Pre-segmentation Step for Page Layout Analysis and Classification.- Robust Super-Resolution Using a Median Filter for Irregular Samples.- Left Ventricle Segmentation from Heart MDCT.- A Comparison of Wavelet Based Spatio-temporal Decomposition Methods for Dynamic Texture Recognition.- A Fast Anisotropic Mumford-Shah Functional Based Segmentation.- Labeling Still Image Databases Using Graphical Models.- Pattern Recognition.- AdaBoost Multiple Feature Selection and Combination for Face Recognition.- Median Graph Computation by Means of a Genetic Approach Based on Minimum Common Supergraph and Maximum Common Subgraph.- Fatty Liver Characterization and Classification by Ultrasound.- Sleep/Wakefulness State from Actigraphy.- A Random Extension for Discriminative Dimensionality Reduction and Metric Learning.- Minimum Error-Rate Training in Statistical Machine Translation Using Structural SVMs.- Morpheme-Based Automatic SpeechRecognition of Basque.- On a Kernel Regression Approach to Machine Translation.- Experimental Analysis of Insertion Costs in a Naïve Dynamic MDF-Tree.- An Approach to Estimate Perplexity Values for Language Models Based on Phrase Classes.- An Adaptive Approach for Affine-Invariant 2D Shape Description.- Towards Real-Time Human Action Recognition.- Using One-Class Classification Techniques in the Anti-phoneme Problem.- Index of Balanced Accuracy: A Performance Measure for Skewed Class Distributions.- Chromatographic Pattern Recognition Using Optimized One-Class Classifiers.- Variable Order Finite-Context Models in DNA Sequence Coding.- Characterizing Graphs Using Spherical Triangles.- Score Fusion by Maximizing the Area under the ROC Curve.- Gender Recognition from a Partial View of the Face Using Local Feature Vectors.- Melodic Track Identification in MIDI Files Considering the Imbalanced Context.- Bernoulli HMMs at Subword Level for Handwritten Word Recognition.- Simultaneous Identity and Expression Recognition Using Face Geometry on Low Dimensional Manifolds.