-#ifdef IDCT_SCALING_SUPPORTED
-
- /* Compute actual output image dimensions and DCT scaling choices. */
- if (cinfo->scale_num * 8 <= cinfo->scale_denom) {
- /* Provide 1/8 scaling */
- cinfo->output_width = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_width, 8L);
- cinfo->output_height = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_height, 8L);
- cinfo->min_DCT_scaled_size = 1;
- } else if (cinfo->scale_num * 4 <= cinfo->scale_denom) {
- /* Provide 1/4 scaling */
- cinfo->output_width = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_width, 4L);
- cinfo->output_height = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_height, 4L);
- cinfo->min_DCT_scaled_size = 2;
- } else if (cinfo->scale_num * 2 <= cinfo->scale_denom) {
- /* Provide 1/2 scaling */
- cinfo->output_width = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_width, 2L);
- cinfo->output_height = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_height, 2L);
- cinfo->min_DCT_scaled_size = 4;
- } else {
- /* Provide 1/1 scaling */
- cinfo->output_width = cinfo->image_width;
- cinfo->output_height = cinfo->image_height;
- cinfo->min_DCT_scaled_size = DCTSIZE;
- }
- /* In selecting the actual DCT scaling for each component, we try to
- * scale up the chroma components via IDCT scaling rather than upsampling.
- * This saves time if the upsampler gets to use 1:1 scaling.
- * Note this code assumes that the supported DCT scalings are powers of 2.
- */
- for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
- ci++, compptr++) {
- int ssize = cinfo->min_DCT_scaled_size;
- while (ssize < DCTSIZE &&
- (compptr->h_samp_factor * ssize * 2 <=
- cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) &&
- (compptr->v_samp_factor * ssize * 2 <=
- cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size)) {
- ssize = ssize * 2;
- }
- compptr->DCT_scaled_size = ssize;
- }
-
- /* Recompute downsampled dimensions of components;
- * application needs to know these if using raw downsampled data.
- */
- for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
- ci++, compptr++) {
- /* Size in samples, after IDCT scaling */
- compptr->downsampled_width = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_width *
- (long) (compptr->h_samp_factor * compptr->DCT_scaled_size),
- (long) (cinfo->max_h_samp_factor * DCTSIZE));
- compptr->downsampled_height = (JDIMENSION)
- jdiv_round_up((long) cinfo->image_height *
- (long) (compptr->v_samp_factor * compptr->DCT_scaled_size),
- (long) (cinfo->max_v_samp_factor * DCTSIZE));
- }
-
-#else /* !IDCT_SCALING_SUPPORTED */
-
- /* Hardwire it to "no scaling" */
- cinfo->output_width = cinfo->image_width;
- cinfo->output_height = cinfo->image_height;
- /* jdinput.c has already initialized DCT_scaled_size to DCTSIZE,
- * and has computed unscaled downsampled_width and downsampled_height.
- */
-
-#endif /* IDCT_SCALING_SUPPORTED */