The present disclosure includes systems and techniques relating to identifying function samples for use in interpolation. In general, in one implementation, the technique includes: obtaining a set of unevenly spaced sample points, x, and corresponding sample outputs, y, of a function y=f(x) within a domain; generating a data structure including first locations corresponding to a set of evenly spaced sample points within the domain, wherein the first locations store index values corresponding to second locations storing the sample outputs, y; receiving an input value of image data; identifying one of the first locations corresponding to the input value; finding two index values stored in the first locations using the one of the first locations as a starting point; and generating an image data output value corresponding to the input value by interpolation using two sample outputs, y, obtained from the second locations using the two index values.