ref: 1bfde841484fadb1c41f41a6279e7e070f61a31b
dir: /sys/src/cmd/gs/jpeg/jcprepct.c/
/* * jcprepct.c * * Copyright (C) 1994-1996, Thomas G. Lane. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. * * This file contains the compression preprocessing controller. * This controller manages the color conversion, downsampling, * and edge expansion steps. * * Most of the complexity here is associated with buffering input rows * as required by the downsampler. See the comments at the head of * jcsample.c for the downsampler's needs. */ #define JPEG_INTERNALS #include "jinclude.h" #include "jpeglib.h" /* At present, jcsample.c can request context rows only for smoothing. * In the future, we might also need context rows for CCIR601 sampling * or other more-complex downsampling procedures. The code to support * context rows should be compiled only if needed. */ #ifdef INPUT_SMOOTHING_SUPPORTED #define CONTEXT_ROWS_SUPPORTED #endif /* * For the simple (no-context-row) case, we just need to buffer one * row group's worth of pixels for the downsampling step. At the bottom of * the image, we pad to a full row group by replicating the last pixel row. * The downsampler's last output row is then replicated if needed to pad * out to a full iMCU row. * * When providing context rows, we must buffer three row groups' worth of * pixels. Three row groups are physically allocated, but the row pointer * arrays are made five row groups high, with the extra pointers above and * below "wrapping around" to point to the last and first real row groups. * This allows the downsampler to access the proper context rows. * At the top and bottom of the image, we create dummy context rows by * copying the first or last real pixel row. This copying could be avoided * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the * trouble on the compression side. */ /* Private buffer controller object */ typedef struct { struct jpeg_c_prep_controller pub; /* public fields */ /* Downsampling input buffer. This buffer holds color-converted data * until we have enough to do a downsample step. */ JSAMPARRAY color_buf[MAX_COMPONENTS]; JDIMENSION rows_to_go; /* counts rows remaining in source image */ int next_buf_row; /* index of next row to store in color_buf */ #ifdef CONTEXT_ROWS_SUPPORTED /* only needed for context case */ int this_row_group; /* starting row index of group to process */ int next_buf_stop; /* downsample when we reach this index */ #endif } my_prep_controller; typedef my_prep_controller * my_prep_ptr; /* * Initialize for a processing pass. */ METHODDEF(void) start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode) { my_prep_ptr prep = (my_prep_ptr) cinfo->prep; if (pass_mode != JBUF_PASS_THRU) ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); /* Initialize total-height counter for detecting bottom of image */ prep->rows_to_go = cinfo->image_height; /* Mark the conversion buffer empty */ prep->next_buf_row = 0; #ifdef CONTEXT_ROWS_SUPPORTED /* Preset additional state variables for context mode. * These aren't used in non-context mode, so we needn't test which mode. */ prep->this_row_group = 0; /* Set next_buf_stop to stop after two row groups have been read in. */ prep->next_buf_stop = 2 * cinfo->max_v_samp_factor; #endif } /* * Expand an image vertically from height input_rows to height output_rows, * by duplicating the bottom row. */ LOCAL(void) expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols, int input_rows, int output_rows) { register int row; for (row = input_rows; row < output_rows; row++) { jcopy_sample_rows(image_data, input_rows-1, image_data, row, 1, num_cols); } } /* * Process some data in the simple no-context case. * * Preprocessor output data is counted in "row groups". A row group * is defined to be v_samp_factor sample rows of each component. * Downsampling will produce this much data from each max_v_samp_factor * input rows. */ METHODDEF(void) pre_process_data (j_compress_ptr cinfo, JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail, JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, JDIMENSION out_row_groups_avail) { my_prep_ptr prep = (my_prep_ptr) cinfo->prep; int numrows, ci; JDIMENSION inrows; jpeg_component_info * compptr; while (*in_row_ctr < in_rows_avail && *out_row_group_ctr < out_row_groups_avail) { /* Do color conversion to fill the conversion buffer. */ inrows = in_rows_avail - *in_row_ctr; numrows = cinfo->max_v_samp_factor - prep->next_buf_row; numrows = (int) MIN((JDIMENSION) numrows, inrows); (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, prep->color_buf, (JDIMENSION) prep->next_buf_row, numrows); *in_row_ctr += numrows; prep->next_buf_row += numrows; prep->rows_to_go -= numrows; /* If at bottom of image, pad to fill the conversion buffer. */ if (prep->rows_to_go == 0 && prep->next_buf_row < cinfo->max_v_samp_factor) { for (ci = 0; ci < cinfo->num_components; ci++) { expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, prep->next_buf_row, cinfo->max_v_samp_factor); } prep->next_buf_row = cinfo->max_v_samp_factor; } /* If we've filled the conversion buffer, empty it. */ if (prep->next_buf_row == cinfo->max_v_samp_factor) { (*cinfo->downsample->downsample) (cinfo, prep->color_buf, (JDIMENSION) 0, output_buf, *out_row_group_ctr); prep->next_buf_row = 0; (*out_row_group_ctr)++; } /* If at bottom of image, pad the output to a full iMCU height. * Note we assume the caller is providing a one-iMCU-height output buffer! */ if (prep->rows_to_go == 0 && *out_row_group_ctr < out_row_groups_avail) { for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) { expand_bottom_edge(output_buf[ci], compptr->width_in_blocks * DCTSIZE, (int) (*out_row_group_ctr * compptr->v_samp_factor), (int) (out_row_groups_avail * compptr->v_samp_factor)); } *out_row_group_ctr = out_row_groups_avail; break; /* can exit outer loop without test */ } } } #ifdef CONTEXT_ROWS_SUPPORTED /* * Process some data in the context case. */ METHODDEF(void) pre_process_context (j_compress_ptr cinfo, JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail, JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, JDIMENSION out_row_groups_avail) { my_prep_ptr prep = (my_prep_ptr) cinfo->prep; int numrows, ci; int buf_height = cinfo->max_v_samp_factor * 3; JDIMENSION inrows; while (*out_row_group_ctr < out_row_groups_avail) { if (*in_row_ctr < in_rows_avail) { /* Do color conversion to fill the conversion buffer. */ inrows = in_rows_avail - *in_row_ctr; numrows = prep->next_buf_stop - prep->next_buf_row; numrows = (int) MIN((JDIMENSION) numrows, inrows); (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, prep->color_buf, (JDIMENSION) prep->next_buf_row, numrows); /* Pad at top of image, if first time through */ if (prep->rows_to_go == cinfo->image_height) { for (ci = 0; ci < cinfo->num_components; ci++) { int row; for (row = 1; row <= cinfo->max_v_samp_factor; row++) { jcopy_sample_rows(prep->color_buf[ci], 0, prep->color_buf[ci], -row, 1, cinfo->image_width); } } } *in_row_ctr += numrows; prep->next_buf_row += numrows; prep->rows_to_go -= numrows; } else { /* Return for more data, unless we are at the bottom of the image. */ if (prep->rows_to_go != 0) break; /* When at bottom of image, pad to fill the conversion buffer. */ if (prep->next_buf_row < prep->next_buf_stop) { for (ci = 0; ci < cinfo->num_components; ci++) { expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, prep->next_buf_row, prep->next_buf_stop); } prep->next_buf_row = prep->next_buf_stop; } } /* If we've gotten enough data, downsample a row group. */ if (prep->next_buf_row == prep->next_buf_stop) { (*cinfo->downsample->downsample) (cinfo, prep->color_buf, (JDIMENSION) prep->this_row_group, output_buf, *out_row_group_ctr); (*out_row_group_ctr)++; /* Advance pointers with wraparound as necessary. */ prep->this_row_group += cinfo->max_v_samp_factor; if (prep->this_row_group >= buf_height) prep->this_row_group = 0; if (prep->next_buf_row >= buf_height) prep->next_buf_row = 0; prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor; } } } /* * Create the wrapped-around downsampling input buffer needed for context mode. */ LOCAL(void) create_context_buffer (j_compress_ptr cinfo) { my_prep_ptr prep = (my_prep_ptr) cinfo->prep; int rgroup_height = cinfo->max_v_samp_factor; int ci, i; jpeg_component_info * compptr; JSAMPARRAY true_buffer, fake_buffer; /* Grab enough space for fake row pointers for all the components; * we need five row groups' worth of pointers for each component. */ fake_buffer = (JSAMPARRAY) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (cinfo->num_components * 5 * rgroup_height) * SIZEOF(JSAMPROW)); for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) { /* Allocate the actual buffer space (3 row groups) for this component. * We make the buffer wide enough to allow the downsampler to edge-expand * horizontally within the buffer, if it so chooses. */ true_buffer = (*cinfo->mem->alloc_sarray) ((j_common_ptr) cinfo, JPOOL_IMAGE, (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * cinfo->max_h_samp_factor) / compptr->h_samp_factor), (JDIMENSION) (3 * rgroup_height)); /* Copy true buffer row pointers into the middle of the fake row array */ MEMCOPY(fake_buffer + rgroup_height, true_buffer, 3 * rgroup_height * SIZEOF(JSAMPROW)); /* Fill in the above and below wraparound pointers */ for (i = 0; i < rgroup_height; i++) { fake_buffer[i] = true_buffer[2 * rgroup_height + i]; fake_buffer[4 * rgroup_height + i] = true_buffer[i]; } prep->color_buf[ci] = fake_buffer + rgroup_height; fake_buffer += 5 * rgroup_height; /* point to space for next component */ } } #endif /* CONTEXT_ROWS_SUPPORTED */ /* * Initialize preprocessing controller. */ GLOBAL(void) jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer) { my_prep_ptr prep; int ci; jpeg_component_info * compptr; if (need_full_buffer) /* safety check */ ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); prep = (my_prep_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_prep_controller)); cinfo->prep = (struct jpeg_c_prep_controller *) prep; prep->pub.start_pass = start_pass_prep; /* Allocate the color conversion buffer. * We make the buffer wide enough to allow the downsampler to edge-expand * horizontally within the buffer, if it so chooses. */ if (cinfo->downsample->need_context_rows) { /* Set up to provide context rows */ #ifdef CONTEXT_ROWS_SUPPORTED prep->pub.pre_process_data = pre_process_context; create_context_buffer(cinfo); #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif } else { /* No context, just make it tall enough for one row group */ prep->pub.pre_process_data = pre_process_data; for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) { prep->color_buf[ci] = (*cinfo->mem->alloc_sarray) ((j_common_ptr) cinfo, JPOOL_IMAGE, (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * cinfo->max_h_samp_factor) / compptr->h_samp_factor), (JDIMENSION) cinfo->max_v_samp_factor); } } }