Bilinear pixel interpolation is a common operation in image processing applications (resizing, distorting, etc.) as well as in computer graphics (texturing, etc.). It allows accessing pixels at non-integer coordinates of the underlying image by building a weighted sum over all neighbors of the specified image position. On GPUs this operation is implemented in hardware. However, some algorithms can not be ported to the GPU easily and a CPU implementation of the Bilinear interpolation is needed.This article will show how to efficiently implement such an operation in C++ using SSE2 instructions for 8-bit RGBA images. First, we will show how to perform bilinear interpolation using pure C++ code and then present an enhanced example where we utilize SSE intrinsics.
