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Diffstat (limited to 'src/libjpeg/jdmainct.c')
| -rw-r--r-- | src/libjpeg/jdmainct.c | 512 |
1 files changed, 512 insertions, 0 deletions
diff --git a/src/libjpeg/jdmainct.c b/src/libjpeg/jdmainct.c new file mode 100644 index 0000000..13c956f --- /dev/null +++ b/src/libjpeg/jdmainct.c @@ -0,0 +1,512 @@ +/* + * jdmainct.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 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. + */ + +#define JPEG_INTERNALS +#include "jinclude.h" +#include "jpeglib.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. + */ + + +/* Private buffer controller object */ + +typedef struct { + struct jpeg_d_main_controller pub; /* public fields */ + + /* Pointer to allocated workspace (M or M+2 row groups). */ + JSAMPARRAY buffer[MAX_COMPONENTS]; + + boolean buffer_full; /* Have we gotten an iMCU row from decoder? */ + JDIMENSION rowgroup_ctr; /* counts row groups output to postprocessor */ + + /* Remaining fields are only used in the context case. */ + + /* These are the master pointers to the funny-order pointer lists. */ + JSAMPIMAGE xbuffer[2]; /* pointers to weird pointer lists */ + + int whichptr; /* indicates which pointer set is now in use */ + int context_state; /* process_data state machine status */ + JDIMENSION rowgroups_avail; /* row groups available to postprocessor */ + JDIMENSION iMCU_row_ctr; /* counts iMCU rows to detect image top/bot */ +} my_main_controller; + +typedef my_main_controller * my_main_ptr; + +/* context_state values: */ +#define CTX_PREPARE_FOR_IMCU 0 /* need to prepare for MCU row */ +#define CTX_PROCESS_IMCU 1 /* feeding iMCU to postprocessor */ +#define CTX_POSTPONED_ROW 2 /* feeding postponed row group */ + + +/* Forward declarations */ +METHODDEF(void) process_data_simple_main + JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf, + JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)); +METHODDEF(void) process_data_context_main + JPP((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 + JPP((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 = (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->xbuffer[0] = (JSAMPIMAGE) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + cinfo->num_components * 2 * SIZEOF(JSAMPARRAY)); + main->xbuffer[1] = main->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->xbuffer[0][ci] = xbuf; + xbuf += rgroup * (M + 4); + main->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->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 = (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->xbuffer[0][ci]; + xbuf1 = main->xbuffer[1][ci]; + /* First copy the workspace pointers as-is */ + buf = main->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_wraparound_pointers (j_decompress_ptr cinfo) +/* Set up the "wraparound" pointers at top and bottom of the pointer lists. + * This changes the pointer list state from top-of-image to the normal state. + */ +{ + my_main_ptr main = (my_main_ptr) cinfo->main; + int ci, i, rgroup; + int M = cinfo->min_DCT_scaled_size; + jpeg_component_info *compptr; + JSAMPARRAY 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->xbuffer[0][ci]; + xbuf1 = main->xbuffer[1][ci]; + for (i = 0; i < rgroup; i++) { + xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i]; + xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i]; + xbuf0[rgroup*(M+2) + i] = xbuf0[i]; + xbuf1[rgroup*(M+2) + i] = xbuf1[i]; + } + } +} + + +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 = (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->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->xbuffer[main->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 = (my_main_ptr) cinfo->main; + + switch (pass_mode) { + case JBUF_PASS_THRU: + if (cinfo->upsample->need_context_rows) { + main->pub.process_data = process_data_context_main; + make_funny_pointers(cinfo); /* Create the xbuffer[] lists */ + main->whichptr = 0; /* Read first iMCU row into xbuffer[0] */ + main->context_state = CTX_PREPARE_FOR_IMCU; + main->iMCU_row_ctr = 0; + } else { + /* Simple case with no context needed */ + main->pub.process_data = process_data_simple_main; + } + main->buffer_full = FALSE; /* Mark buffer empty */ + main->rowgroup_ctr = 0; + break; +#ifdef QUANT_2PASS_SUPPORTED + case JBUF_CRANK_DEST: + /* For last pass of 2-pass quantization, just crank the postprocessor */ + main->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 = (my_main_ptr) cinfo->main; + JDIMENSION rowgroups_avail; + + /* Read input data if we haven't filled the main buffer yet */ + if (! main->buffer_full) { + if (! (*cinfo->coef->decompress_data) (cinfo, main->buffer)) + return; /* suspension forced, can do nothing more */ + main->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->buffer, + &main->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->rowgroup_ctr >= rowgroups_avail) { + main->buffer_full = FALSE; + main->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 = (my_main_ptr) cinfo->main; + + /* Read input data if we haven't filled the main buffer yet */ + if (! main->buffer_full) { + if (! (*cinfo->coef->decompress_data) (cinfo, + main->xbuffer[main->whichptr])) + return; /* suspension forced, can do nothing more */ + main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */ + main->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->context_state) { + case CTX_POSTPONED_ROW: + /* Call postprocessor using previously set pointers for postponed row */ + (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr], + &main->rowgroup_ctr, main->rowgroups_avail, + output_buf, out_row_ctr, out_rows_avail); + if (main->rowgroup_ctr < main->rowgroups_avail) + return; /* Need to suspend */ + main->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->rowgroup_ctr = 0; + main->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->iMCU_row_ctr == cinfo->total_iMCU_rows) + set_bottom_pointers(cinfo); + main->context_state = CTX_PROCESS_IMCU; + /*FALLTHROUGH*/ + case CTX_PROCESS_IMCU: + /* Call postprocessor using previously set pointers */ + (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr], + &main->rowgroup_ctr, main->rowgroups_avail, + output_buf, out_row_ctr, out_rows_avail); + if (main->rowgroup_ctr < main->rowgroups_avail) + return; /* Need to suspend */ + /* After the first iMCU, change wraparound pointers to normal state */ + if (main->iMCU_row_ctr == 1) + set_wraparound_pointers(cinfo); + /* Prepare to load new iMCU row using other xbuffer list */ + main->whichptr ^= 1; /* 0=>1 or 1=>0 */ + main->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->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1); + main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2); + main->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; + int ci, rgroup, ngroups; + jpeg_component_info *compptr; + + main = (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; + main->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->buffer[ci] = (*cinfo->mem->alloc_sarray) + ((j_common_ptr) cinfo, JPOOL_IMAGE, + compptr->width_in_blocks * compptr->DCT_scaled_size, + (JDIMENSION) (rgroup * ngroups)); + } +} |