| /* |
| * jdmainct.c |
| * |
| * This file was part of the Independent JPEG Group's software: |
| * Copyright (C) 1994-1996, Thomas G. Lane. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2010, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * file. |
| * |
| * This file contains the main buffer controller for decompression. |
| * The main buffer lies between the JPEG decompressor proper and the |
| * post-processor; it holds downsampled data in the JPEG colorspace. |
| * |
| * Note that this code is bypassed in raw-data mode, since the application |
| * supplies the equivalent of the main buffer in that case. |
| */ |
| |
| #include "jdmainct.h" |
| |
| |
| /* |
| * In the current system design, the main buffer need never be a full-image |
| * buffer; any full-height buffers will be found inside the coefficient or |
| * postprocessing controllers. Nonetheless, the main controller is not |
| * trivial. Its responsibility is to provide context rows for upsampling/ |
| * rescaling, and doing this in an efficient fashion is a bit tricky. |
| * |
| * Postprocessor input data is counted in "row groups". A row group |
| * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size) |
| * sample rows of each component. (We require DCT_scaled_size values to be |
| * chosen such that these numbers are integers. In practice DCT_scaled_size |
| * values will likely be powers of two, so we actually have the stronger |
| * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.) |
| * Upsampling will typically produce max_v_samp_factor pixel rows from each |
| * row group (times any additional scale factor that the upsampler is |
| * applying). |
| * |
| * The coefficient controller will deliver data to us one iMCU row at a time; |
| * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or |
| * exactly min_DCT_scaled_size row groups. (This amount of data corresponds |
| * to one row of MCUs when the image is fully interleaved.) Note that the |
| * number of sample rows varies across components, but the number of row |
| * groups does not. Some garbage sample rows may be included in the last iMCU |
| * row at the bottom of the image. |
| * |
| * Depending on the vertical scaling algorithm used, the upsampler may need |
| * access to the sample row(s) above and below its current input row group. |
| * The upsampler is required to set need_context_rows TRUE at global selection |
| * time if so. When need_context_rows is FALSE, this controller can simply |
| * obtain one iMCU row at a time from the coefficient controller and dole it |
| * out as row groups to the postprocessor. |
| * |
| * When need_context_rows is TRUE, this controller guarantees that the buffer |
| * passed to postprocessing contains at least one row group's worth of samples |
| * above and below the row group(s) being processed. Note that the context |
| * rows "above" the first passed row group appear at negative row offsets in |
| * the passed buffer. At the top and bottom of the image, the required |
| * context rows are manufactured by duplicating the first or last real sample |
| * row; this avoids having special cases in the upsampling inner loops. |
| * |
| * The amount of context is fixed at one row group just because that's a |
| * convenient number for this controller to work with. The existing |
| * upsamplers really only need one sample row of context. An upsampler |
| * supporting arbitrary output rescaling might wish for more than one row |
| * group of context when shrinking the image; tough, we don't handle that. |
| * (This is justified by the assumption that downsizing will be handled mostly |
| * by adjusting the DCT_scaled_size values, so that the actual scale factor at |
| * the upsample step needn't be much less than one.) |
| * |
| * To provide the desired context, we have to retain the last two row groups |
| * of one iMCU row while reading in the next iMCU row. (The last row group |
| * can't be processed until we have another row group for its below-context, |
| * and so we have to save the next-to-last group too for its above-context.) |
| * We could do this most simply by copying data around in our buffer, but |
| * that'd be very slow. We can avoid copying any data by creating a rather |
| * strange pointer structure. Here's how it works. We allocate a workspace |
| * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number |
| * of row groups per iMCU row). We create two sets of redundant pointers to |
| * the workspace. Labeling the physical row groups 0 to M+1, the synthesized |
| * pointer lists look like this: |
| * M+1 M-1 |
| * master pointer --> 0 master pointer --> 0 |
| * 1 1 |
| * ... ... |
| * M-3 M-3 |
| * M-2 M |
| * M-1 M+1 |
| * M M-2 |
| * M+1 M-1 |
| * 0 0 |
| * We read alternate iMCU rows using each master pointer; thus the last two |
| * row groups of the previous iMCU row remain un-overwritten in the workspace. |
| * The pointer lists are set up so that the required context rows appear to |
| * be adjacent to the proper places when we pass the pointer lists to the |
| * upsampler. |
| * |
| * The above pictures describe the normal state of the pointer lists. |
| * At top and bottom of the image, we diddle the pointer lists to duplicate |
| * the first or last sample row as necessary (this is cheaper than copying |
| * sample rows around). |
| * |
| * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1. In that |
| * situation each iMCU row provides only one row group so the buffering logic |
| * must be different (eg, we must read two iMCU rows before we can emit the |
| * first row group). For now, we simply do not support providing context |
| * rows when min_DCT_scaled_size is 1. That combination seems unlikely to |
| * be worth providing --- if someone wants a 1/8th-size preview, they probably |
| * want it quick and dirty, so a context-free upsampler is sufficient. |
| */ |
| |
| |
| /* Forward declarations */ |
| METHODDEF(void) process_data_simple_main |
| (j_decompress_ptr cinfo, JSAMPARRAY output_buf, |
| JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail); |
| METHODDEF(void) process_data_context_main |
| (j_decompress_ptr cinfo, JSAMPARRAY output_buf, |
| JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail); |
| #ifdef QUANT_2PASS_SUPPORTED |
| METHODDEF(void) process_data_crank_post |
| (j_decompress_ptr cinfo, JSAMPARRAY output_buf, |
| JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail); |
| #endif |
| |
| |
| LOCAL(void) |
| alloc_funny_pointers (j_decompress_ptr cinfo) |
| /* Allocate space for the funny pointer lists. |
| * This is done only once, not once per pass. |
| */ |
| { |
| my_main_ptr main_ptr = (my_main_ptr) cinfo->main; |
| int ci, rgroup; |
| int M = cinfo->_min_DCT_scaled_size; |
| jpeg_component_info *compptr; |
| JSAMPARRAY xbuf; |
| |
| /* Get top-level space for component array pointers. |
| * We alloc both arrays with one call to save a few cycles. |
| */ |
| main_ptr->xbuffer[0] = (JSAMPIMAGE) |
| (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| cinfo->num_components * 2 * sizeof(JSAMPARRAY)); |
| main_ptr->xbuffer[1] = main_ptr->xbuffer[0] + cinfo->num_components; |
| |
| for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
| ci++, compptr++) { |
| rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) / |
| cinfo->_min_DCT_scaled_size; /* height of a row group of component */ |
| /* Get space for pointer lists --- M+4 row groups in each list. |
| * We alloc both pointer lists with one call to save a few cycles. |
| */ |
| xbuf = (JSAMPARRAY) |
| (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| 2 * (rgroup * (M + 4)) * sizeof(JSAMPROW)); |
| xbuf += rgroup; /* want one row group at negative offsets */ |
| main_ptr->xbuffer[0][ci] = xbuf; |
| xbuf += rgroup * (M + 4); |
| main_ptr->xbuffer[1][ci] = xbuf; |
| } |
| } |
| |
| |
| LOCAL(void) |
| make_funny_pointers (j_decompress_ptr cinfo) |
| /* Create the funny pointer lists discussed in the comments above. |
| * The actual workspace is already allocated (in main_ptr->buffer), |
| * and the space for the pointer lists is allocated too. |
| * This routine just fills in the curiously ordered lists. |
| * This will be repeated at the beginning of each pass. |
| */ |
| { |
| my_main_ptr main_ptr = (my_main_ptr) cinfo->main; |
| int ci, i, rgroup; |
| int M = cinfo->_min_DCT_scaled_size; |
| jpeg_component_info *compptr; |
| JSAMPARRAY buf, xbuf0, xbuf1; |
| |
| for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
| ci++, compptr++) { |
| rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) / |
| cinfo->_min_DCT_scaled_size; /* height of a row group of component */ |
| xbuf0 = main_ptr->xbuffer[0][ci]; |
| xbuf1 = main_ptr->xbuffer[1][ci]; |
| /* First copy the workspace pointers as-is */ |
| buf = main_ptr->buffer[ci]; |
| for (i = 0; i < rgroup * (M + 2); i++) { |
| xbuf0[i] = xbuf1[i] = buf[i]; |
| } |
| /* In the second list, put the last four row groups in swapped order */ |
| for (i = 0; i < rgroup * 2; i++) { |
| xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i]; |
| xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i]; |
| } |
| /* The wraparound pointers at top and bottom will be filled later |
| * (see set_wraparound_pointers, below). Initially we want the "above" |
| * pointers to duplicate the first actual data line. This only needs |
| * to happen in xbuffer[0]. |
| */ |
| for (i = 0; i < rgroup; i++) { |
| xbuf0[i - rgroup] = xbuf0[0]; |
| } |
| } |
| } |
| |
| |
| LOCAL(void) |
| set_bottom_pointers (j_decompress_ptr cinfo) |
| /* Change the pointer lists to duplicate the last sample row at the bottom |
| * of the image. whichptr indicates which xbuffer holds the final iMCU row. |
| * Also sets rowgroups_avail to indicate number of nondummy row groups in row. |
| */ |
| { |
| my_main_ptr main_ptr = (my_main_ptr) cinfo->main; |
| int ci, i, rgroup, iMCUheight, rows_left; |
| jpeg_component_info *compptr; |
| JSAMPARRAY xbuf; |
| |
| for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
| ci++, compptr++) { |
| /* Count sample rows in one iMCU row and in one row group */ |
| iMCUheight = compptr->v_samp_factor * compptr->_DCT_scaled_size; |
| rgroup = iMCUheight / cinfo->_min_DCT_scaled_size; |
| /* Count nondummy sample rows remaining for this component */ |
| rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight); |
| if (rows_left == 0) rows_left = iMCUheight; |
| /* Count nondummy row groups. Should get same answer for each component, |
| * so we need only do it once. |
| */ |
| if (ci == 0) { |
| main_ptr->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1); |
| } |
| /* Duplicate the last real sample row rgroup*2 times; this pads out the |
| * last partial rowgroup and ensures at least one full rowgroup of context. |
| */ |
| xbuf = main_ptr->xbuffer[main_ptr->whichptr][ci]; |
| for (i = 0; i < rgroup * 2; i++) { |
| xbuf[rows_left + i] = xbuf[rows_left-1]; |
| } |
| } |
| } |
| |
| |
| /* |
| * Initialize for a processing pass. |
| */ |
| |
| METHODDEF(void) |
| start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode) |
| { |
| my_main_ptr main_ptr = (my_main_ptr) cinfo->main; |
| |
| switch (pass_mode) { |
| case JBUF_PASS_THRU: |
| if (cinfo->upsample->need_context_rows) { |
| main_ptr->pub.process_data = process_data_context_main; |
| make_funny_pointers(cinfo); /* Create the xbuffer[] lists */ |
| main_ptr->whichptr = 0; /* Read first iMCU row into xbuffer[0] */ |
| main_ptr->context_state = CTX_PREPARE_FOR_IMCU; |
| main_ptr->iMCU_row_ctr = 0; |
| } else { |
| /* Simple case with no context needed */ |
| main_ptr->pub.process_data = process_data_simple_main; |
| } |
| main_ptr->buffer_full = FALSE; /* Mark buffer empty */ |
| main_ptr->rowgroup_ctr = 0; |
| break; |
| #ifdef QUANT_2PASS_SUPPORTED |
| case JBUF_CRANK_DEST: |
| /* For last pass of 2-pass quantization, just crank the postprocessor */ |
| main_ptr->pub.process_data = process_data_crank_post; |
| break; |
| #endif |
| default: |
| ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
| break; |
| } |
| } |
| |
| |
| /* |
| * Process some data. |
| * This handles the simple case where no context is required. |
| */ |
| |
| METHODDEF(void) |
| process_data_simple_main (j_decompress_ptr cinfo, |
| JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
| JDIMENSION out_rows_avail) |
| { |
| my_main_ptr main_ptr = (my_main_ptr) cinfo->main; |
| JDIMENSION rowgroups_avail; |
| |
| /* Read input data if we haven't filled the main buffer yet */ |
| if (! main_ptr->buffer_full) { |
| if (! (*cinfo->coef->decompress_data) (cinfo, main_ptr->buffer)) |
| return; /* suspension forced, can do nothing more */ |
| main_ptr->buffer_full = TRUE; /* OK, we have an iMCU row to work with */ |
| } |
| |
| /* There are always min_DCT_scaled_size row groups in an iMCU row. */ |
| rowgroups_avail = (JDIMENSION) cinfo->_min_DCT_scaled_size; |
| /* Note: at the bottom of the image, we may pass extra garbage row groups |
| * to the postprocessor. The postprocessor has to check for bottom |
| * of image anyway (at row resolution), so no point in us doing it too. |
| */ |
| |
| /* Feed the postprocessor */ |
| (*cinfo->post->post_process_data) (cinfo, main_ptr->buffer, |
| &main_ptr->rowgroup_ctr, rowgroups_avail, |
| output_buf, out_row_ctr, out_rows_avail); |
| |
| /* Has postprocessor consumed all the data yet? If so, mark buffer empty */ |
| if (main_ptr->rowgroup_ctr >= rowgroups_avail) { |
| main_ptr->buffer_full = FALSE; |
| main_ptr->rowgroup_ctr = 0; |
| } |
| } |
| |
| |
| /* |
| * Process some data. |
| * This handles the case where context rows must be provided. |
| */ |
| |
| METHODDEF(void) |
| process_data_context_main (j_decompress_ptr cinfo, |
| JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
| JDIMENSION out_rows_avail) |
| { |
| my_main_ptr main_ptr = (my_main_ptr) cinfo->main; |
| |
| /* Read input data if we haven't filled the main buffer yet */ |
| if (! main_ptr->buffer_full) { |
| if (! (*cinfo->coef->decompress_data) (cinfo, |
| main_ptr->xbuffer[main_ptr->whichptr])) |
| return; /* suspension forced, can do nothing more */ |
| main_ptr->buffer_full = TRUE; /* OK, we have an iMCU row to work with */ |
| main_ptr->iMCU_row_ctr++; /* count rows received */ |
| } |
| |
| /* Postprocessor typically will not swallow all the input data it is handed |
| * in one call (due to filling the output buffer first). Must be prepared |
| * to exit and restart. This switch lets us keep track of how far we got. |
| * Note that each case falls through to the next on successful completion. |
| */ |
| switch (main_ptr->context_state) { |
| case CTX_POSTPONED_ROW: |
| /* Call postprocessor using previously set pointers for postponed row */ |
| (*cinfo->post->post_process_data) (cinfo, main_ptr->xbuffer[main_ptr->whichptr], |
| &main_ptr->rowgroup_ctr, main_ptr->rowgroups_avail, |
| output_buf, out_row_ctr, out_rows_avail); |
| if (main_ptr->rowgroup_ctr < main_ptr->rowgroups_avail) |
| return; /* Need to suspend */ |
| main_ptr->context_state = CTX_PREPARE_FOR_IMCU; |
| if (*out_row_ctr >= out_rows_avail) |
| return; /* Postprocessor exactly filled output buf */ |
| /*FALLTHROUGH*/ |
| case CTX_PREPARE_FOR_IMCU: |
| /* Prepare to process first M-1 row groups of this iMCU row */ |
| main_ptr->rowgroup_ctr = 0; |
| main_ptr->rowgroups_avail = (JDIMENSION) (cinfo->_min_DCT_scaled_size - 1); |
| /* Check for bottom of image: if so, tweak pointers to "duplicate" |
| * the last sample row, and adjust rowgroups_avail to ignore padding rows. |
| */ |
| if (main_ptr->iMCU_row_ctr == cinfo->total_iMCU_rows) |
| set_bottom_pointers(cinfo); |
| main_ptr->context_state = CTX_PROCESS_IMCU; |
| /*FALLTHROUGH*/ |
| case CTX_PROCESS_IMCU: |
| /* Call postprocessor using previously set pointers */ |
| (*cinfo->post->post_process_data) (cinfo, main_ptr->xbuffer[main_ptr->whichptr], |
| &main_ptr->rowgroup_ctr, main_ptr->rowgroups_avail, |
| output_buf, out_row_ctr, out_rows_avail); |
| if (main_ptr->rowgroup_ctr < main_ptr->rowgroups_avail) |
| return; /* Need to suspend */ |
| /* After the first iMCU, change wraparound pointers to normal state */ |
| if (main_ptr->iMCU_row_ctr == 1) |
| set_wraparound_pointers(cinfo); |
| /* Prepare to load new iMCU row using other xbuffer list */ |
| main_ptr->whichptr ^= 1; /* 0=>1 or 1=>0 */ |
| main_ptr->buffer_full = FALSE; |
| /* Still need to process last row group of this iMCU row, */ |
| /* which is saved at index M+1 of the other xbuffer */ |
| main_ptr->rowgroup_ctr = (JDIMENSION) (cinfo->_min_DCT_scaled_size + 1); |
| main_ptr->rowgroups_avail = (JDIMENSION) (cinfo->_min_DCT_scaled_size + 2); |
| main_ptr->context_state = CTX_POSTPONED_ROW; |
| } |
| } |
| |
| |
| /* |
| * Process some data. |
| * Final pass of two-pass quantization: just call the postprocessor. |
| * Source data will be the postprocessor controller's internal buffer. |
| */ |
| |
| #ifdef QUANT_2PASS_SUPPORTED |
| |
| METHODDEF(void) |
| process_data_crank_post (j_decompress_ptr cinfo, |
| JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
| JDIMENSION out_rows_avail) |
| { |
| (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL, |
| (JDIMENSION *) NULL, (JDIMENSION) 0, |
| output_buf, out_row_ctr, out_rows_avail); |
| } |
| |
| #endif /* QUANT_2PASS_SUPPORTED */ |
| |
| |
| /* |
| * Initialize main buffer controller. |
| */ |
| |
| GLOBAL(void) |
| jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer) |
| { |
| my_main_ptr main_ptr; |
| int ci, rgroup, ngroups; |
| jpeg_component_info *compptr; |
| |
| main_ptr = (my_main_ptr) |
| (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| sizeof(my_main_controller)); |
| cinfo->main = (struct jpeg_d_main_controller *) main_ptr; |
| main_ptr->pub.start_pass = start_pass_main; |
| |
| if (need_full_buffer) /* shouldn't happen */ |
| ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
| |
| /* Allocate the workspace. |
| * ngroups is the number of row groups we need. |
| */ |
| if (cinfo->upsample->need_context_rows) { |
| if (cinfo->_min_DCT_scaled_size < 2) /* unsupported, see comments above */ |
| ERREXIT(cinfo, JERR_NOTIMPL); |
| alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */ |
| ngroups = cinfo->_min_DCT_scaled_size + 2; |
| } else { |
| ngroups = cinfo->_min_DCT_scaled_size; |
| } |
| |
| for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
| ci++, compptr++) { |
| rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) / |
| cinfo->_min_DCT_scaled_size; /* height of a row group of component */ |
| main_ptr->buffer[ci] = (*cinfo->mem->alloc_sarray) |
| ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| compptr->width_in_blocks * compptr->_DCT_scaled_size, |
| (JDIMENSION) (rgroup * ngroups)); |
| } |
| } |
