| /* |
| * jdapistd.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, 2015-2020, 2022, D. R. Commander. |
| * Copyright (C) 2015, Google, Inc. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * file. |
| * |
| * This file contains application interface code for the decompression half |
| * of the JPEG library. These are the "standard" API routines that are |
| * used in the normal full-decompression case. They are not used by a |
| * transcoding-only application. Note that if an application links in |
| * jpeg_start_decompress, it will end up linking in the entire decompressor. |
| * We thus must separate this file from jdapimin.c to avoid linking the |
| * whole decompression library into a transcoder. |
| */ |
| |
| #include "jinclude.h" |
| #if BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED) |
| #include "jdmainct.h" |
| #include "jdcoefct.h" |
| #else |
| #define JPEG_INTERNALS |
| #include "jpeglib.h" |
| #endif |
| #include "jdmaster.h" |
| #include "jdmerge.h" |
| #include "jdsample.h" |
| #include "jmemsys.h" |
| |
| #if BITS_IN_JSAMPLE == 8 |
| |
| /* Forward declarations */ |
| LOCAL(boolean) output_pass_setup(j_decompress_ptr cinfo); |
| |
| |
| /* |
| * Decompression initialization. |
| * jpeg_read_header must be completed before calling this. |
| * |
| * If a multipass operating mode was selected, this will do all but the |
| * last pass, and thus may take a great deal of time. |
| * |
| * Returns FALSE if suspended. The return value need be inspected only if |
| * a suspending data source is used. |
| */ |
| |
| GLOBAL(boolean) |
| jpeg_start_decompress(j_decompress_ptr cinfo) |
| { |
| if (cinfo->global_state == DSTATE_READY) { |
| /* First call: initialize master control, select active modules */ |
| jinit_master_decompress(cinfo); |
| if (cinfo->buffered_image) { |
| /* No more work here; expecting jpeg_start_output next */ |
| cinfo->global_state = DSTATE_BUFIMAGE; |
| return TRUE; |
| } |
| cinfo->global_state = DSTATE_PRELOAD; |
| } |
| if (cinfo->global_state == DSTATE_PRELOAD) { |
| /* If file has multiple scans, absorb them all into the coef buffer */ |
| if (cinfo->inputctl->has_multiple_scans) { |
| #ifdef D_MULTISCAN_FILES_SUPPORTED |
| for (;;) { |
| int retcode; |
| /* Call progress monitor hook if present */ |
| if (cinfo->progress != NULL) |
| (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
| /* Absorb some more input */ |
| retcode = (*cinfo->inputctl->consume_input) (cinfo); |
| if (retcode == JPEG_SUSPENDED) |
| return FALSE; |
| if (retcode == JPEG_REACHED_EOI) |
| break; |
| /* Advance progress counter if appropriate */ |
| if (cinfo->progress != NULL && |
| (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { |
| if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { |
| /* jdmaster underestimated number of scans; ratchet up one scan */ |
| cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows; |
| } |
| } |
| } |
| #else |
| ERREXIT(cinfo, JERR_NOT_COMPILED); |
| #endif /* D_MULTISCAN_FILES_SUPPORTED */ |
| } |
| cinfo->output_scan_number = cinfo->input_scan_number; |
| } else if (cinfo->global_state != DSTATE_PRESCAN) |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| /* Perform any dummy output passes, and set up for the final pass */ |
| return output_pass_setup(cinfo); |
| } |
| |
| |
| /* |
| * Set up for an output pass, and perform any dummy pass(es) needed. |
| * Common subroutine for jpeg_start_decompress and jpeg_start_output. |
| * Entry: global_state = DSTATE_PRESCAN only if previously suspended. |
| * Exit: If done, returns TRUE and sets global_state for proper output mode. |
| * If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN. |
| */ |
| |
| LOCAL(boolean) |
| output_pass_setup(j_decompress_ptr cinfo) |
| { |
| if (cinfo->global_state != DSTATE_PRESCAN) { |
| /* First call: do pass setup */ |
| (*cinfo->master->prepare_for_output_pass) (cinfo); |
| cinfo->output_scanline = 0; |
| cinfo->global_state = DSTATE_PRESCAN; |
| } |
| /* Loop over any required dummy passes */ |
| while (cinfo->master->is_dummy_pass) { |
| #ifdef QUANT_2PASS_SUPPORTED |
| /* Crank through the dummy pass */ |
| while (cinfo->output_scanline < cinfo->output_height) { |
| JDIMENSION last_scanline; |
| /* Call progress monitor hook if present */ |
| if (cinfo->progress != NULL) { |
| cinfo->progress->pass_counter = (long)cinfo->output_scanline; |
| cinfo->progress->pass_limit = (long)cinfo->output_height; |
| (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
| } |
| /* Process some data */ |
| last_scanline = cinfo->output_scanline; |
| #ifdef D_LOSSLESS_SUPPORTED |
| if (cinfo->data_precision == 16) |
| (*cinfo->main->process_data_16) (cinfo, (J16SAMPARRAY)NULL, |
| &cinfo->output_scanline, |
| (JDIMENSION)0); |
| else |
| #endif |
| if (cinfo->data_precision == 12) |
| (*cinfo->main->process_data_12) (cinfo, (J12SAMPARRAY)NULL, |
| &cinfo->output_scanline, |
| (JDIMENSION)0); |
| else |
| (*cinfo->main->process_data) (cinfo, (JSAMPARRAY)NULL, |
| &cinfo->output_scanline, (JDIMENSION)0); |
| if (cinfo->output_scanline == last_scanline) |
| return FALSE; /* No progress made, must suspend */ |
| } |
| /* Finish up dummy pass, and set up for another one */ |
| (*cinfo->master->finish_output_pass) (cinfo); |
| (*cinfo->master->prepare_for_output_pass) (cinfo); |
| cinfo->output_scanline = 0; |
| #else |
| ERREXIT(cinfo, JERR_NOT_COMPILED); |
| #endif /* QUANT_2PASS_SUPPORTED */ |
| } |
| /* Ready for application to drive output pass through |
| * _jpeg_read_scanlines or _jpeg_read_raw_data. |
| */ |
| cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING; |
| return TRUE; |
| } |
| |
| #endif /* BITS_IN_JSAMPLE == 8 */ |
| |
| |
| #if BITS_IN_JSAMPLE != 16 |
| |
| /* |
| * Enable partial scanline decompression |
| * |
| * Must be called after jpeg_start_decompress() and before any calls to |
| * _jpeg_read_scanlines() or _jpeg_skip_scanlines(). |
| * |
| * Refer to libjpeg.txt for more information. |
| */ |
| |
| GLOBAL(void) |
| _jpeg_crop_scanline(j_decompress_ptr cinfo, JDIMENSION *xoffset, |
| JDIMENSION *width) |
| { |
| int ci, align, orig_downsampled_width; |
| JDIMENSION input_xoffset; |
| boolean reinit_upsampler = FALSE; |
| jpeg_component_info *compptr; |
| #ifdef UPSAMPLE_MERGING_SUPPORTED |
| my_master_ptr master = (my_master_ptr)cinfo->master; |
| #endif |
| |
| if (cinfo->data_precision != BITS_IN_JSAMPLE) |
| ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); |
| |
| if (cinfo->master->lossless) |
| ERREXIT(cinfo, JERR_NOTIMPL); |
| |
| if ((cinfo->global_state != DSTATE_SCANNING && |
| cinfo->global_state != DSTATE_BUFIMAGE) || cinfo->output_scanline != 0) |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| |
| if (!xoffset || !width) |
| ERREXIT(cinfo, JERR_BAD_CROP_SPEC); |
| |
| /* xoffset and width must fall within the output image dimensions. */ |
| if (*width == 0 || *xoffset + *width > cinfo->output_width) |
| ERREXIT(cinfo, JERR_WIDTH_OVERFLOW); |
| |
| /* No need to do anything if the caller wants the entire width. */ |
| if (*width == cinfo->output_width) |
| return; |
| |
| /* Ensuring the proper alignment of xoffset is tricky. At minimum, it |
| * must align with an MCU boundary, because: |
| * |
| * (1) The IDCT is performed in blocks, and it is not feasible to modify |
| * the algorithm so that it can transform partial blocks. |
| * (2) Because of the SIMD extensions, any input buffer passed to the |
| * upsampling and color conversion routines must be aligned to the |
| * SIMD word size (for instance, 128-bit in the case of SSE2.) The |
| * easiest way to accomplish this without copying data is to ensure |
| * that upsampling and color conversion begin at the start of the |
| * first MCU column that will be inverse transformed. |
| * |
| * In practice, we actually impose a stricter alignment requirement. We |
| * require that xoffset be a multiple of the maximum MCU column width of all |
| * of the components (the "iMCU column width.") This is to simplify the |
| * single-pass decompression case, allowing us to use the same MCU column |
| * width for all of the components. |
| */ |
| if (cinfo->comps_in_scan == 1 && cinfo->num_components == 1) |
| align = cinfo->_min_DCT_scaled_size; |
| else |
| align = cinfo->_min_DCT_scaled_size * cinfo->max_h_samp_factor; |
| |
| /* Adjust xoffset to the nearest iMCU boundary <= the requested value */ |
| input_xoffset = *xoffset; |
| *xoffset = (input_xoffset / align) * align; |
| |
| /* Adjust the width so that the right edge of the output image is as |
| * requested (only the left edge is altered.) It is important that calling |
| * programs check this value after this function returns, so that they can |
| * allocate an output buffer with the appropriate size. |
| */ |
| *width = *width + input_xoffset - *xoffset; |
| cinfo->output_width = *width; |
| #ifdef UPSAMPLE_MERGING_SUPPORTED |
| if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) { |
| my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample; |
| upsample->out_row_width = |
| cinfo->output_width * cinfo->out_color_components; |
| } |
| #endif |
| |
| /* Set the first and last iMCU columns that we must decompress. These values |
| * will be used in single-scan decompressions. |
| */ |
| cinfo->master->first_iMCU_col = (JDIMENSION)(long)(*xoffset) / (long)align; |
| cinfo->master->last_iMCU_col = |
| (JDIMENSION)jdiv_round_up((long)(*xoffset + cinfo->output_width), |
| (long)align) - 1; |
| |
| for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
| ci++, compptr++) { |
| int hsf = (cinfo->comps_in_scan == 1 && cinfo->num_components == 1) ? |
| 1 : compptr->h_samp_factor; |
| |
| /* Set downsampled_width to the new output width. */ |
| orig_downsampled_width = compptr->downsampled_width; |
| compptr->downsampled_width = |
| (JDIMENSION)jdiv_round_up((long)(cinfo->output_width * |
| compptr->h_samp_factor), |
| (long)cinfo->max_h_samp_factor); |
| if (compptr->downsampled_width < 2 && orig_downsampled_width >= 2) |
| reinit_upsampler = TRUE; |
| |
| /* Set the first and last iMCU columns that we must decompress. These |
| * values will be used in multi-scan decompressions. |
| */ |
| cinfo->master->first_MCU_col[ci] = |
| (JDIMENSION)(long)(*xoffset * hsf) / (long)align; |
| cinfo->master->last_MCU_col[ci] = |
| (JDIMENSION)jdiv_round_up((long)((*xoffset + cinfo->output_width) * hsf), |
| (long)align) - 1; |
| } |
| |
| if (reinit_upsampler) { |
| cinfo->master->jinit_upsampler_no_alloc = TRUE; |
| _jinit_upsampler(cinfo); |
| cinfo->master->jinit_upsampler_no_alloc = FALSE; |
| } |
| } |
| |
| #endif /* BITS_IN_JSAMPLE != 16 */ |
| |
| |
| /* |
| * Read some scanlines of data from the JPEG decompressor. |
| * |
| * The return value will be the number of lines actually read. |
| * This may be less than the number requested in several cases, |
| * including bottom of image, data source suspension, and operating |
| * modes that emit multiple scanlines at a time. |
| * |
| * Note: we warn about excess calls to _jpeg_read_scanlines() since |
| * this likely signals an application programmer error. However, |
| * an oversize buffer (max_lines > scanlines remaining) is not an error. |
| */ |
| |
| GLOBAL(JDIMENSION) |
| _jpeg_read_scanlines(j_decompress_ptr cinfo, _JSAMPARRAY scanlines, |
| JDIMENSION max_lines) |
| { |
| #if BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED) |
| JDIMENSION row_ctr; |
| |
| if (cinfo->data_precision != BITS_IN_JSAMPLE) |
| ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); |
| |
| if (cinfo->global_state != DSTATE_SCANNING) |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| if (cinfo->output_scanline >= cinfo->output_height) { |
| WARNMS(cinfo, JWRN_TOO_MUCH_DATA); |
| return 0; |
| } |
| |
| /* Call progress monitor hook if present */ |
| if (cinfo->progress != NULL) { |
| cinfo->progress->pass_counter = (long)cinfo->output_scanline; |
| cinfo->progress->pass_limit = (long)cinfo->output_height; |
| (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
| } |
| |
| /* Process some data */ |
| row_ctr = 0; |
| (*cinfo->main->_process_data) (cinfo, scanlines, &row_ctr, max_lines); |
| cinfo->output_scanline += row_ctr; |
| return row_ctr; |
| #else |
| ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); |
| return 0; |
| #endif |
| } |
| |
| |
| #if BITS_IN_JSAMPLE != 16 |
| |
| /* Dummy color convert function used by _jpeg_skip_scanlines() */ |
| LOCAL(void) |
| noop_convert(j_decompress_ptr cinfo, _JSAMPIMAGE input_buf, |
| JDIMENSION input_row, _JSAMPARRAY output_buf, int num_rows) |
| { |
| } |
| |
| |
| /* Dummy quantize function used by _jpeg_skip_scanlines() */ |
| LOCAL(void) |
| noop_quantize(j_decompress_ptr cinfo, _JSAMPARRAY input_buf, |
| _JSAMPARRAY output_buf, int num_rows) |
| { |
| } |
| |
| |
| /* |
| * In some cases, it is best to call _jpeg_read_scanlines() and discard the |
| * output, rather than skipping the scanlines, because this allows us to |
| * maintain the internal state of the context-based upsampler. In these cases, |
| * we set up and tear down a dummy color converter in order to avoid valgrind |
| * errors and to achieve the best possible performance. |
| */ |
| |
| LOCAL(void) |
| read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines) |
| { |
| JDIMENSION n; |
| #ifdef UPSAMPLE_MERGING_SUPPORTED |
| my_master_ptr master = (my_master_ptr)cinfo->master; |
| #endif |
| _JSAMPLE dummy_sample[1] = { 0 }; |
| _JSAMPROW dummy_row = dummy_sample; |
| _JSAMPARRAY scanlines = NULL; |
| void (*color_convert) (j_decompress_ptr cinfo, _JSAMPIMAGE input_buf, |
| JDIMENSION input_row, _JSAMPARRAY output_buf, |
| int num_rows) = NULL; |
| void (*color_quantize) (j_decompress_ptr cinfo, _JSAMPARRAY input_buf, |
| _JSAMPARRAY output_buf, int num_rows) = NULL; |
| |
| if (cinfo->cconvert && cinfo->cconvert->_color_convert) { |
| color_convert = cinfo->cconvert->_color_convert; |
| cinfo->cconvert->_color_convert = noop_convert; |
| /* This just prevents UBSan from complaining about adding 0 to a NULL |
| * pointer. The pointer isn't actually used. |
| */ |
| scanlines = &dummy_row; |
| } |
| |
| if (cinfo->cquantize && cinfo->cquantize->_color_quantize) { |
| color_quantize = cinfo->cquantize->_color_quantize; |
| cinfo->cquantize->_color_quantize = noop_quantize; |
| } |
| |
| #ifdef UPSAMPLE_MERGING_SUPPORTED |
| if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) { |
| my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample; |
| scanlines = &upsample->spare_row; |
| } |
| #endif |
| |
| for (n = 0; n < num_lines; n++) |
| _jpeg_read_scanlines(cinfo, scanlines, 1); |
| |
| if (color_convert) |
| cinfo->cconvert->_color_convert = color_convert; |
| |
| if (color_quantize) |
| cinfo->cquantize->_color_quantize = color_quantize; |
| } |
| |
| |
| /* |
| * Called by _jpeg_skip_scanlines(). This partially skips a decompress block |
| * by incrementing the rowgroup counter. |
| */ |
| |
| LOCAL(void) |
| increment_simple_rowgroup_ctr(j_decompress_ptr cinfo, JDIMENSION rows) |
| { |
| JDIMENSION rows_left; |
| my_main_ptr main_ptr = (my_main_ptr)cinfo->main; |
| my_master_ptr master = (my_master_ptr)cinfo->master; |
| |
| if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) { |
| read_and_discard_scanlines(cinfo, rows); |
| return; |
| } |
| |
| /* Increment the counter to the next row group after the skipped rows. */ |
| main_ptr->rowgroup_ctr += rows / cinfo->max_v_samp_factor; |
| |
| /* Partially skipping a row group would involve modifying the internal state |
| * of the upsampler, so read the remaining rows into a dummy buffer instead. |
| */ |
| rows_left = rows % cinfo->max_v_samp_factor; |
| cinfo->output_scanline += rows - rows_left; |
| |
| read_and_discard_scanlines(cinfo, rows_left); |
| } |
| |
| /* |
| * Skips some scanlines of data from the JPEG decompressor. |
| * |
| * The return value will be the number of lines actually skipped. If skipping |
| * num_lines would move beyond the end of the image, then the actual number of |
| * lines remaining in the image is returned. Otherwise, the return value will |
| * be equal to num_lines. |
| * |
| * Refer to libjpeg.txt for more information. |
| */ |
| |
| GLOBAL(JDIMENSION) |
| _jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines) |
| { |
| my_main_ptr main_ptr = (my_main_ptr)cinfo->main; |
| my_coef_ptr coef = (my_coef_ptr)cinfo->coef; |
| my_master_ptr master = (my_master_ptr)cinfo->master; |
| my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample; |
| JDIMENSION i, x; |
| int y; |
| JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row; |
| JDIMENSION lines_to_skip, lines_to_read; |
| |
| if (cinfo->data_precision != BITS_IN_JSAMPLE) |
| ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); |
| |
| if (cinfo->master->lossless) |
| ERREXIT(cinfo, JERR_NOTIMPL); |
| |
| /* Two-pass color quantization is not supported. */ |
| if (cinfo->quantize_colors && cinfo->two_pass_quantize) |
| ERREXIT(cinfo, JERR_NOTIMPL); |
| |
| if (cinfo->global_state != DSTATE_SCANNING) |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| |
| /* Do not skip past the bottom of the image. */ |
| if (cinfo->output_scanline + num_lines >= cinfo->output_height) { |
| num_lines = cinfo->output_height - cinfo->output_scanline; |
| cinfo->output_scanline = cinfo->output_height; |
| (*cinfo->inputctl->finish_input_pass) (cinfo); |
| cinfo->inputctl->eoi_reached = TRUE; |
| return num_lines; |
| } |
| |
| if (num_lines == 0) |
| return 0; |
| |
| lines_per_iMCU_row = cinfo->_min_DCT_scaled_size * cinfo->max_v_samp_factor; |
| lines_left_in_iMCU_row = |
| (lines_per_iMCU_row - (cinfo->output_scanline % lines_per_iMCU_row)) % |
| lines_per_iMCU_row; |
| lines_after_iMCU_row = num_lines - lines_left_in_iMCU_row; |
| |
| /* Skip the lines remaining in the current iMCU row. When upsampling |
| * requires context rows, we need the previous and next rows in order to read |
| * the current row. This adds some complexity. |
| */ |
| if (cinfo->upsample->need_context_rows) { |
| /* If the skipped lines would not move us past the current iMCU row, we |
| * read the lines and ignore them. There might be a faster way of doing |
| * this, but we are facing increasing complexity for diminishing returns. |
| * The increasing complexity would be a by-product of meddling with the |
| * state machine used to skip context rows. Near the end of an iMCU row, |
| * the next iMCU row may have already been entropy-decoded. In this unique |
| * case, we will read the next iMCU row if we cannot skip past it as well. |
| */ |
| if ((num_lines < lines_left_in_iMCU_row + 1) || |
| (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full && |
| lines_after_iMCU_row < lines_per_iMCU_row + 1)) { |
| read_and_discard_scanlines(cinfo, num_lines); |
| return num_lines; |
| } |
| |
| /* If the next iMCU row has already been entropy-decoded, make sure that |
| * we do not skip too far. |
| */ |
| if (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full) { |
| cinfo->output_scanline += lines_left_in_iMCU_row + lines_per_iMCU_row; |
| lines_after_iMCU_row -= lines_per_iMCU_row; |
| } else { |
| cinfo->output_scanline += lines_left_in_iMCU_row; |
| } |
| |
| /* If we have just completed the first block, adjust the buffer pointers */ |
| if (main_ptr->iMCU_row_ctr == 0 || |
| (main_ptr->iMCU_row_ctr == 1 && lines_left_in_iMCU_row > 2)) |
| set_wraparound_pointers(cinfo); |
| main_ptr->buffer_full = FALSE; |
| main_ptr->rowgroup_ctr = 0; |
| main_ptr->context_state = CTX_PREPARE_FOR_IMCU; |
| if (!master->using_merged_upsample) { |
| upsample->next_row_out = cinfo->max_v_samp_factor; |
| upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
| } |
| } |
| |
| /* Skipping is much simpler when context rows are not required. */ |
| else { |
| if (num_lines < lines_left_in_iMCU_row) { |
| increment_simple_rowgroup_ctr(cinfo, num_lines); |
| return num_lines; |
| } else { |
| cinfo->output_scanline += lines_left_in_iMCU_row; |
| main_ptr->buffer_full = FALSE; |
| main_ptr->rowgroup_ctr = 0; |
| if (!master->using_merged_upsample) { |
| upsample->next_row_out = cinfo->max_v_samp_factor; |
| upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
| } |
| } |
| } |
| |
| /* Calculate how many full iMCU rows we can skip. */ |
| if (cinfo->upsample->need_context_rows) |
| lines_to_skip = ((lines_after_iMCU_row - 1) / lines_per_iMCU_row) * |
| lines_per_iMCU_row; |
| else |
| lines_to_skip = (lines_after_iMCU_row / lines_per_iMCU_row) * |
| lines_per_iMCU_row; |
| /* Calculate the number of lines that remain to be skipped after skipping all |
| * of the full iMCU rows that we can. We will not read these lines unless we |
| * have to. |
| */ |
| lines_to_read = lines_after_iMCU_row - lines_to_skip; |
| |
| /* For images requiring multiple scans (progressive, non-interleaved, etc.), |
| * all of the entropy decoding occurs in jpeg_start_decompress(), assuming |
| * that the input data source is non-suspending. This makes skipping easy. |
| */ |
| if (cinfo->inputctl->has_multiple_scans || cinfo->buffered_image) { |
| if (cinfo->upsample->need_context_rows) { |
| cinfo->output_scanline += lines_to_skip; |
| cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row; |
| main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row; |
| /* It is complex to properly move to the middle of a context block, so |
| * read the remaining lines instead of skipping them. |
| */ |
| read_and_discard_scanlines(cinfo, lines_to_read); |
| } else { |
| cinfo->output_scanline += lines_to_skip; |
| cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row; |
| increment_simple_rowgroup_ctr(cinfo, lines_to_read); |
| } |
| if (!master->using_merged_upsample) |
| upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
| return num_lines; |
| } |
| |
| /* Skip the iMCU rows that we can safely skip. */ |
| for (i = 0; i < lines_to_skip; i += lines_per_iMCU_row) { |
| for (y = 0; y < coef->MCU_rows_per_iMCU_row; y++) { |
| for (x = 0; x < cinfo->MCUs_per_row; x++) { |
| /* Calling decode_mcu() with a NULL pointer causes it to discard the |
| * decoded coefficients. This is ~5% faster for large subsets, but |
| * it's tough to tell a difference for smaller images. |
| */ |
| if (!cinfo->entropy->insufficient_data) |
| cinfo->master->last_good_iMCU_row = cinfo->input_iMCU_row; |
| (*cinfo->entropy->decode_mcu) (cinfo, NULL); |
| } |
| } |
| cinfo->input_iMCU_row++; |
| cinfo->output_iMCU_row++; |
| if (cinfo->input_iMCU_row < cinfo->total_iMCU_rows) |
| start_iMCU_row(cinfo); |
| else |
| (*cinfo->inputctl->finish_input_pass) (cinfo); |
| } |
| cinfo->output_scanline += lines_to_skip; |
| |
| if (cinfo->upsample->need_context_rows) { |
| /* Context-based upsampling keeps track of iMCU rows. */ |
| main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row; |
| |
| /* It is complex to properly move to the middle of a context block, so |
| * read the remaining lines instead of skipping them. |
| */ |
| read_and_discard_scanlines(cinfo, lines_to_read); |
| } else { |
| increment_simple_rowgroup_ctr(cinfo, lines_to_read); |
| } |
| |
| /* Since skipping lines involves skipping the upsampling step, the value of |
| * "rows_to_go" will become invalid unless we set it here. NOTE: This is a |
| * bit odd, since "rows_to_go" seems to be redundantly keeping track of |
| * output_scanline. |
| */ |
| if (!master->using_merged_upsample) |
| upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
| |
| /* Always skip the requested number of lines. */ |
| return num_lines; |
| } |
| |
| /* |
| * Alternate entry point to read raw data. |
| * Processes exactly one iMCU row per call, unless suspended. |
| */ |
| |
| GLOBAL(JDIMENSION) |
| _jpeg_read_raw_data(j_decompress_ptr cinfo, _JSAMPIMAGE data, |
| JDIMENSION max_lines) |
| { |
| JDIMENSION lines_per_iMCU_row; |
| |
| if (cinfo->data_precision != BITS_IN_JSAMPLE) |
| ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); |
| |
| if (cinfo->master->lossless) |
| ERREXIT(cinfo, JERR_NOTIMPL); |
| |
| if (cinfo->global_state != DSTATE_RAW_OK) |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| if (cinfo->output_scanline >= cinfo->output_height) { |
| WARNMS(cinfo, JWRN_TOO_MUCH_DATA); |
| return 0; |
| } |
| |
| /* Call progress monitor hook if present */ |
| if (cinfo->progress != NULL) { |
| cinfo->progress->pass_counter = (long)cinfo->output_scanline; |
| cinfo->progress->pass_limit = (long)cinfo->output_height; |
| (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
| } |
| |
| /* Verify that at least one iMCU row can be returned. */ |
| lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size; |
| if (max_lines < lines_per_iMCU_row) |
| ERREXIT(cinfo, JERR_BUFFER_SIZE); |
| |
| /* Decompress directly into user's buffer. */ |
| if (!(*cinfo->coef->_decompress_data) (cinfo, data)) |
| return 0; /* suspension forced, can do nothing more */ |
| |
| /* OK, we processed one iMCU row. */ |
| cinfo->output_scanline += lines_per_iMCU_row; |
| return lines_per_iMCU_row; |
| } |
| |
| #endif /* BITS_IN_JSAMPLE != 16 */ |
| |
| |
| #if BITS_IN_JSAMPLE == 8 |
| |
| /* Additional entry points for buffered-image mode. */ |
| |
| #ifdef D_MULTISCAN_FILES_SUPPORTED |
| |
| /* |
| * Initialize for an output pass in buffered-image mode. |
| */ |
| |
| GLOBAL(boolean) |
| jpeg_start_output(j_decompress_ptr cinfo, int scan_number) |
| { |
| if (cinfo->global_state != DSTATE_BUFIMAGE && |
| cinfo->global_state != DSTATE_PRESCAN) |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| /* Limit scan number to valid range */ |
| if (scan_number <= 0) |
| scan_number = 1; |
| if (cinfo->inputctl->eoi_reached && scan_number > cinfo->input_scan_number) |
| scan_number = cinfo->input_scan_number; |
| cinfo->output_scan_number = scan_number; |
| /* Perform any dummy output passes, and set up for the real pass */ |
| return output_pass_setup(cinfo); |
| } |
| |
| |
| /* |
| * Finish up after an output pass in buffered-image mode. |
| * |
| * Returns FALSE if suspended. The return value need be inspected only if |
| * a suspending data source is used. |
| */ |
| |
| GLOBAL(boolean) |
| jpeg_finish_output(j_decompress_ptr cinfo) |
| { |
| if ((cinfo->global_state == DSTATE_SCANNING || |
| cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) { |
| /* Terminate this pass. */ |
| /* We do not require the whole pass to have been completed. */ |
| (*cinfo->master->finish_output_pass) (cinfo); |
| cinfo->global_state = DSTATE_BUFPOST; |
| } else if (cinfo->global_state != DSTATE_BUFPOST) { |
| /* BUFPOST = repeat call after a suspension, anything else is error */ |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
| } |
| /* Read markers looking for SOS or EOI */ |
| while (cinfo->input_scan_number <= cinfo->output_scan_number && |
| !cinfo->inputctl->eoi_reached) { |
| if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED) |
| return FALSE; /* Suspend, come back later */ |
| } |
| cinfo->global_state = DSTATE_BUFIMAGE; |
| return TRUE; |
| } |
| |
| #endif /* D_MULTISCAN_FILES_SUPPORTED */ |
| |
| #endif /* BITS_IN_JSAMPLE == 8 */ |