Scanline algorithms in compressed domain

The scanline algorithms are popular in a computer graphics for complex geometric manipulations. The main characteristic of the scanline algorithms is that a geometric transformation is decomposed into multiples transforms with each pass operating only along row or column scanlines. This leads to conversion of 2D image manipulation problems to straightforward 1D problems resulting in simple and systematic methods. The goal of this work is to examine the scanline approach for manipulation of transform-compressed images without decompressing them. We show how the scanline algorithms for rotation and projective mapping can be developed for JPEG/DCT images. The performance of the proposed scanline algorithms is evaluated with respect to quality, speed, and control and memory overhead.