| /* |
| * jcprepct.c |
| * |
| * This file is part of the Independent JPEG Group's software: |
| * Copyright (C) 1994-1996, Thomas G. Lane. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2022, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * 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 */ |
| memcpy(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); |
| } |
| } |
| } |