* jfdctfst.c
*
* Copyright (C) 1994-1996, Thomas G. Lane.
+ * Modified 2003-2009 by Guido Vollbeding.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
*/
GLOBAL(void)
-jpeg_fdct_ifast (DCTELEM * data)
+jpeg_fdct_ifast (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
{
DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
DCTELEM tmp10, tmp11, tmp12, tmp13;
DCTELEM z1, z2, z3, z4, z5, z11, z13;
DCTELEM *dataptr;
+ JSAMPROW elemptr;
int ctr;
SHIFT_TEMPS
/* Pass 1: process rows. */
dataptr = data;
- for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
- tmp0 = dataptr[0] + dataptr[7];
- tmp7 = dataptr[0] - dataptr[7];
- tmp1 = dataptr[1] + dataptr[6];
- tmp6 = dataptr[1] - dataptr[6];
- tmp2 = dataptr[2] + dataptr[5];
- tmp5 = dataptr[2] - dataptr[5];
- tmp3 = dataptr[3] + dataptr[4];
- tmp4 = dataptr[3] - dataptr[4];
+ for (ctr = 0; ctr < DCTSIZE; ctr++) {
+ elemptr = sample_data[ctr] + start_col;
+
+ /* Load data into workspace */
+ tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]);
+ tmp7 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]);
+ tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]);
+ tmp6 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]);
+ tmp2 = GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]);
+ tmp5 = GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]);
+ tmp3 = GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]);
+ tmp4 = GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]);
/* Even part */
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
- dataptr[0] = tmp10 + tmp11; /* phase 3 */
+ /* Apply unsigned->signed conversion */
+ dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
dataptr[4] = tmp10 - tmp11;
z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */