- unsigned max_samp_h = 2, max_samp_v = 2;
-
- unsigned nw0 = nominal_w * samp_h0 / max_samp_h, nh0 = nominal_h * samp_v0 / max_samp_v;
- unsigned nw1 = nominal_w * samp_h1 / max_samp_h, nh1 = nominal_h * samp_v1 / max_samp_v;
- unsigned nw2 = nominal_w * samp_h2 / max_samp_h, nh2 = nominal_h * samp_v2 / max_samp_v;
-
- unsigned stride0 = (nw0 + DCTSIZE-1) & ~(DCTSIZE-1);
- unsigned stride1 = (nw1 + DCTSIZE-1) & ~(DCTSIZE-1);
- unsigned stride2 = (nw2 + DCTSIZE-1) & ~(DCTSIZE-1);
-
- struct jpeg_decompress_struct dinfo;
- struct jpeg_error_mgr jerr;
- dinfo.err = jpeg_std_error(&jerr);
- jpeg_create_decompress(&dinfo);
- jpeg_stdio_src(&dinfo, stdin);
- jpeg_read_header(&dinfo, TRUE);
- dinfo.raw_data_out = TRUE;
- jpeg_start_decompress(&dinfo);
-
- fprintf(stderr, "Scaling using Lanczos filter:\n");
- fprintf(stderr, " Y component: %ux%u -> %ux%u\n", dinfo.comp_info[0].width_in_blocks * DCTSIZE, dinfo.comp_info[0].height_in_blocks * DCTSIZE, nw0, nh0);
- fprintf(stderr, " Cb component: %ux%u -> %ux%u\n", dinfo.comp_info[1].width_in_blocks * DCTSIZE, dinfo.comp_info[1].height_in_blocks * DCTSIZE, nw1, nh1);
- fprintf(stderr, " Cr component: %ux%u -> %ux%u\n", dinfo.comp_info[2].width_in_blocks * DCTSIZE, dinfo.comp_info[2].height_in_blocks * DCTSIZE, nw2, nh2);
-
- float *npix_y = (float *)malloc((dinfo.comp_info[0].height_in_blocks + dinfo.comp_info[0].v_samp_factor - 1) * DCTSIZE * stride0 * sizeof(float));
- float *npix_cb = (float *)malloc((dinfo.comp_info[1].height_in_blocks + dinfo.comp_info[1].v_samp_factor - 1) * DCTSIZE * stride1 * sizeof(float));
- float *npix_cr = (float *)malloc((dinfo.comp_info[2].height_in_blocks + dinfo.comp_info[2].v_samp_factor - 1) * DCTSIZE * stride2 * sizeof(float));
- JSAMPLE *data_y = (unsigned char *)malloc(nh0 * stride0);
- JSAMPLE *data_cb = (unsigned char *)malloc(nh1 * stride1);
- JSAMPLE *data_cr = (unsigned char *)malloc(nh2 * stride2);
-
- struct filter filt0, filt1, filt2;
-
- hscale_calc_filter(&filt0,
- /* w= */ dinfo.image_width * dinfo.comp_info[0].h_samp_factor / dinfo.max_h_samp_factor,
- /* h= */ dinfo.comp_info[0].v_samp_factor * DCTSIZE,
- /* nw= */ nw0
- );
- hscale_calc_filter(&filt1,
- /* w= */ dinfo.image_width * dinfo.comp_info[1].h_samp_factor / dinfo.max_h_samp_factor,
- /* h= */ dinfo.comp_info[1].v_samp_factor * DCTSIZE,
- /* nw= */ nw1
- );
- hscale_calc_filter(&filt2,
- /* w= */ dinfo.image_width * dinfo.comp_info[2].h_samp_factor / dinfo.max_h_samp_factor,
- /* h= */ dinfo.comp_info[2].v_samp_factor * DCTSIZE,
- /* nw= */ nw2
- );
-
- int total_lines = 0, blocks = 0;
- while (total_lines < dinfo.comp_info[0].height_in_blocks * DCTSIZE) {
- unsigned max_lines = dinfo.max_v_samp_factor * DCTSIZE;
- JSAMPLE tmp_y [(dinfo.comp_info[0].width_in_blocks * DCTSIZE) * (DCTSIZE * dinfo.comp_info[0].v_samp_factor)];
- JSAMPLE tmp_cb[(dinfo.comp_info[1].width_in_blocks * DCTSIZE) * (DCTSIZE * dinfo.comp_info[1].v_samp_factor)];
- JSAMPLE tmp_cr[(dinfo.comp_info[2].width_in_blocks * DCTSIZE) * (DCTSIZE * dinfo.comp_info[2].v_samp_factor)];
-
- JSAMPROW y_row_ptrs[max_lines];
- JSAMPROW cb_row_ptrs[max_lines];
- JSAMPROW cr_row_ptrs[max_lines];
- JSAMPROW* ptrs[] = { y_row_ptrs, cb_row_ptrs, cr_row_ptrs };
- int i;
-
- for (i = 0; i < max_lines; ++i) {
- y_row_ptrs[i] = tmp_y + i * dinfo.comp_info[0].width_in_blocks * DCTSIZE;
- cb_row_ptrs[i] = tmp_cb + i * dinfo.comp_info[1].width_in_blocks * DCTSIZE;
- cr_row_ptrs[i] = tmp_cr + i * dinfo.comp_info[2].width_in_blocks * DCTSIZE;
- }
-
- int lines = jpeg_read_raw_data(&dinfo, ptrs, max_lines);
- if (lines == 0)
- break;
-
- hscale(/* filter= */ &filt0,
- /* from= */ tmp_y,
- /* to= */ npix_y + blocks * DCTSIZE * dinfo.comp_info[0].v_samp_factor * stride0,
- /* w= */ dinfo.image_width * dinfo.comp_info[0].h_samp_factor / dinfo.max_h_samp_factor,
- /* h= */ dinfo.comp_info[0].v_samp_factor * DCTSIZE,
- /* nw= */ nw0,
- /* sstride= */ dinfo.comp_info[0].width_in_blocks * DCTSIZE,
- /* dstride= */ stride0);
-
- hscale(/* filter= */ &filt1,
- /* from= */ tmp_cb,
- /* to= */ npix_cb + blocks * DCTSIZE * dinfo.comp_info[1].v_samp_factor * stride1,
- /* w= */ dinfo.image_width * dinfo.comp_info[1].h_samp_factor / dinfo.max_h_samp_factor,
- /* h= */ dinfo.comp_info[1].v_samp_factor * DCTSIZE,
- /* nw= */ nw1,
- /* sstride= */ dinfo.comp_info[1].width_in_blocks * DCTSIZE,
- /* dstride= */ stride1);
-
- hscale(/* filter= */ &filt2,
- /* from= */ tmp_cr,
- /* to= */ npix_cr + blocks * DCTSIZE * dinfo.comp_info[2].v_samp_factor * stride2,
- /* w= */ dinfo.image_width * dinfo.comp_info[2].h_samp_factor / dinfo.max_h_samp_factor,
- /* h= */ dinfo.comp_info[2].v_samp_factor * DCTSIZE,
- /* nw= */ nw2,
- /* sstride= */ dinfo.comp_info[2].width_in_blocks * DCTSIZE,
- /* dstride= */ stride2);
-
- total_lines += max_lines;
- ++blocks;
- }
-
- vscale(npix_y, data_y, stride0, dinfo.image_height * dinfo.comp_info[0].v_samp_factor / dinfo.max_v_samp_factor, nh0, stride0);
- vscale(npix_cb, data_cb, stride1, dinfo.image_height * dinfo.comp_info[1].v_samp_factor / dinfo.max_v_samp_factor, nh1, stride1);
- vscale(npix_cr, data_cr, stride2, dinfo.image_height * dinfo.comp_info[2].v_samp_factor / dinfo.max_v_samp_factor, nh2, stride2);
- jpeg_destroy_decompress(&dinfo);
-
- struct jpeg_compress_struct cinfo;
- cinfo.err = jpeg_std_error(&jerr);
- jpeg_create_compress(&cinfo);
- jpeg_stdio_dest(&cinfo, stdout);
- cinfo.input_components = 3;
- jpeg_set_defaults(&cinfo);
- jpeg_set_quality(&cinfo, 85, FALSE);
- cinfo.image_width = nominal_w;
- cinfo.image_height = nominal_h;
- cinfo.raw_data_in = TRUE;
- jpeg_set_colorspace(&cinfo, JCS_YCbCr);
- cinfo.comp_info[0].h_samp_factor = samp_h0;
- cinfo.comp_info[0].v_samp_factor = samp_v0;
- cinfo.comp_info[1].h_samp_factor = samp_h1;
- cinfo.comp_info[1].v_samp_factor = samp_v1;
- cinfo.comp_info[2].h_samp_factor = samp_h2;
- cinfo.comp_info[2].v_samp_factor = samp_v2;
- jpeg_start_compress(&cinfo, TRUE);
-
- total_lines = 0;
- blocks = 0;
- while (total_lines < cinfo.comp_info[0].height_in_blocks * DCTSIZE) {
- unsigned max_lines = cinfo.max_v_samp_factor * DCTSIZE;
-
- JSAMPROW y_row_ptrs[max_lines];
- JSAMPROW cb_row_ptrs[max_lines];
- JSAMPROW cr_row_ptrs[max_lines];
- JSAMPROW* ptrs[] = { y_row_ptrs, cb_row_ptrs, cr_row_ptrs };
- int i;
-
- for (i = 0; i < max_lines; ++i) {
- // simple edge extension
- int yline = i + blocks*DCTSIZE*cinfo.comp_info[0].v_samp_factor;
- if (yline > nh0 - 1)
- yline = nh0 - 1;
-
- int cbline = i + blocks*DCTSIZE*cinfo.comp_info[1].v_samp_factor;
- if (cbline > nh1 - 1)
- cbline = nh1 - 1;
-
- int crline = i + blocks*DCTSIZE*cinfo.comp_info[2].v_samp_factor;
- if (crline > nh2 - 1)
- crline = nh2 - 1;
-
- y_row_ptrs[i] = data_y + yline * stride0;
- cb_row_ptrs[i] = data_cb + cbline * stride1;
- cr_row_ptrs[i] = data_cr + crline * stride2;
- }
-
- total_lines += max_lines;
- ++blocks;