Abstract: A method and apparatus for, in response to receiving a request, retrieving digital images that are associated with one or more keywords and which are similar to a digital image is provided. The request may be processed using a keywords index and a content index, and optionally, a session index that references data about what digital images users have viewed together in a session. A category associated with the identified digital image may also be used in processing the request, e.g., the category associated with the identified digital image may change the weight placed on various content attributes used in comparing the content of the identified digital image to other digital images. After the set of requested digital images are determined, request data, that identifies the set of requested digital images, may be sent to the requestor.

Abstract: A method and apparatus for comparing content attributes, e.g., texture, of one digital image a second digital image. An image operation is performed on gray scale image data to identify intensity transitions of a first digital image. The gray scale image data comprises a set of data values that each identifies a gray scale value. For at least a subset of the set of data values, a slope value for an intensity transition associated with the data value is determined. The slope values are converted to possible slope values of a bounded set of possible slope values. First slope data that describes a frequency of occurrence, across the subset of data values, of each possible slope value is generated. The first slope data is compared to second slope data associated with the second digital image to determine how similar the first digital image is to the second digital image.

Abstract: A method and apparatus for comparing the content attributes, e.g., color, of one digital image to the content attributes of a second digital image. A plurality of image regions for a first digital image is determined. Each of the plurality of image regions corresponds to an area of the first digital image that is associated with a different color. Color distribution data that describes a size of each image region is determined. A determination is made as to whether the first digital image is similar in visual appearance to a second digital image. This approach may be used to compare how similar the first digital image is to a plurality of other digital images. A ranking may also be determined that expresses a relative similarity between the first digital image to a plurality of other digital images whose visual appearance was compared to the first digital image.