Illumination estimation using natural scene statistics

A computer-implemented method for training an illumination classifier, the method comprising:

• computing, with one or more processors, ground truth white balance gains for each training image of a plurality of training images;
• clustering, with the one or more processors, the training images into reference illumination classes based on the ground truth white balance gains;
• deriving, with the one or more processors, feature vectors for each training image in each reference illumination class;
• training, with the one or more processors, an illumination classifier for the reference illumination classes based on the feature vectors, wherein classification parameters for each reference illumination class are determined;
• and
• performing illumination estimation on an image based on the illumination classifier.

An apparatus configured to estimate illumination of an image, the apparatus comprising:

• means for computing ground truth white balance gains for each training image of a plurality of training images;
• means for clustering the training images into reference illumination classes based on the ground truth white balance gains;
• means for deriving feature vectors for each training image in each reference illumination class;
• means for training an illumination classifier based on the feature vectors, wherein classification parameters for each reference illumination class are determined;
• means for capturing the image;
• means for computing a feature vector for the image;
• means for identifying at least one best reference illumination class for the image from the reference illumination classes using the feature vector for the image, the illumination classifier, and the classification parameters corresponding to each reference illumination class;
• means for computing information for further processing of the image based on the at least one best reference illumination class, wherein the information is at least one selected from a group consisting of color temperature and white balance gains;
• and
• means for performing further processing on the image based on the information.