0N/A * reserved comment block 0N/A * DO NOT REMOVE OR ALTER! 0N/A * Copyright (C) 1994-1996, Thomas G. Lane. 0N/A * This file is part of the Independent JPEG Group's software. 0N/A * For conditions of distribution and use, see the accompanying README file. 0N/A * This file contains a floating-point implementation of the 0N/A * forward DCT (Discrete Cosine Transform). 0N/A * This implementation should be more accurate than either of the integer 0N/A * DCT implementations. However, it may not give the same results on all 0N/A * machines because of differences in roundoff behavior. Speed will depend 0N/A * on the hardware's floating point capacity. 0N/A * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT 0N/A * on each column. Direct algorithms are also available, but they are 0N/A * much more complex and seem not to be any faster when reduced to code. 0N/A * This implementation is based on Arai, Agui, and Nakajima's algorithm for 0N/A * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in 0N/A * Japanese, but the algorithm is described in the Pennebaker & Mitchell 0N/A * JPEG textbook (see REFERENCES section in file README). The following code 0N/A * is based directly on figure 4-8 in P&M. 0N/A * While an 8-point DCT cannot be done in less than 11 multiplies, it is 0N/A * possible to arrange the computation so that many of the multiplies are 0N/A * simple scalings of the final outputs. These multiplies can then be 0N/A * folded into the multiplications or divisions by the JPEG quantization 0N/A * table entries. The AA&N method leaves only 5 multiplies and 29 adds 0N/A * to be done in the DCT itself. 0N/A * The primary disadvantage of this method is that with a fixed-point 0N/A * implementation, accuracy is lost due to imprecise representation of the 0N/A * scaled quantization values. However, that problem does not arise if 0N/A * we use floating point arithmetic. 0N/A#
include "jdct.h" /* Private declarations for DCT subsystem */ 0N/A * This module is specialized to the case DCTSIZE = 8. 0N/A * Perform the forward DCT on one block of samples. 0N/A /* Pass 1: process rows. */ 0N/A /* The rotator is modified from fig 4-8 to avoid extra negations. */ 0N/A /* Pass 2: process columns. */ 0N/A /* The rotator is modified from fig 4-8 to avoid extra negations. */ 0N/A#
endif /* DCT_FLOAT_SUPPORTED */