Advances in technologies for scanning, networking, and CD-ROM, lower prices for large disk storage, and acceptance of common image compression and file formats have contributed to an increase in the number, size, and uses of on-line image collections. New tools are needed to help users create, manage, and retrieve images from these collections. We are developing QBIC (query by image content), a prototype system that allows a user to create and query image databases in which the image content -- the colors, textures, shapes, and layout of images and the objects they contain -- is used as the basis of queries. This paper describes two sets of algorithms in QBIC. The first are methods that allow `query by color drawing,' a form of query in which a user draws an approximate color version of an image, and similar images are retrieved. These are automatic algorithms in the sense that no user action is necessary during database population. Secondly, we describe algorithms for semi-automatic identification of image objects during database population, improving the speed and usability of this manually-intensive step. Once outlined, detailed queries on the content-properties of these individual objects can be made at query time.