// * jdmaster.c // * // * Copyright (C) 1991-1995, 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 master control logic for the JPEG decompressor. // * These routines are concerned with selecting the modules to be executed // * and with determining the number of passes and the work to be done in each // * pass. #define JPEG_INTERNALS #include "JINCLUDE.h" #include "JPEGLIB.h" // Private state typedef struct { struct jpeg_decomp_master pub; // public fields int pass_number; // # of passes completed boolean using_merged_upsample; // TRUE if using merged upsample/cconvert // Saved references to initialized quantizer modules, // * in case we need to switch modes. struct jpeg_color_quantizer * quantizer_1pass; struct jpeg_color_quantizer * quantizer_2pass; } my_decomp_master; typedef my_decomp_master * my_master_ptr; // * Determine whether merged upsample/color conversion should be used. // * CRUCIAL: this must match the actual capabilities of jdmerge.c! LOCAL boolean use_merged_upsample (j_decompress_ptr cinfo) { #ifdef UPSAMPLE_MERGING_SUPPORTED // Merging is the equivalent of plain box-filter upsampling if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling) return FALSE; // jdmerge.c only supports YCC=>RGB color conversion if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 || cinfo->out_color_space != JCS_RGB || cinfo->out_color_components != RGB_PIXELSIZE) return FALSE; // and it only handles 2h1v or 2h2v sampling ratios if (cinfo->comp_info[0].h_samp_factor != 2 || cinfo->comp_info[1].h_samp_factor != 1 || cinfo->comp_info[2].h_samp_factor != 1 || cinfo->comp_info[0].v_samp_factor > 2 || cinfo->comp_info[1].v_samp_factor != 1 || cinfo->comp_info[2].v_samp_factor != 1) return FALSE; // furthermore, it doesn't work if we've scaled the IDCTs differently if (cinfo->comp_info[0].DCT_scaled_size != cinfo->min_DCT_scaled_size || cinfo->comp_info[1].DCT_scaled_size != cinfo->min_DCT_scaled_size || cinfo->comp_info[2].DCT_scaled_size != cinfo->min_DCT_scaled_size) return FALSE; // ??? also need to test for upsample-time rescaling, when & if supported return TRUE; // by golly, it'll work... #else return FALSE; #endif } // * Compute output image dimensions and related values. // * NOTE: this is exported for possible use by application. // * Hence it mustn't do anything that can't be done twice. // * Also note that it may be called before the master module is initialized! GLOBAL void jpeg_calc_output_dimensions (j_decompress_ptr cinfo) // Do computations that are needed before master selection phase { int ci; jpeg_component_info *compptr; // Prevent application from calling me at wrong times if (cinfo->global_state != DSTATE_READY) ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); #ifdef IDCT_SCALING_SUPPORTED // Compute actual output image dimensions and DCT scaling choices. if (cinfo->scale_num * 8 <= cinfo->scale_denom) { // Provide 1/8 scaling cinfo->output_width = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_width, 8L); cinfo->output_height = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_height, 8L); cinfo->min_DCT_scaled_size = 1; } else if (cinfo->scale_num * 4 <= cinfo->scale_denom) { // Provide 1/4 scaling cinfo->output_width = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_width, 4L); cinfo->output_height = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_height, 4L); cinfo->min_DCT_scaled_size = 2; } else if (cinfo->scale_num * 2 <= cinfo->scale_denom) { // Provide 1/2 scaling cinfo->output_width = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_width, 2L); cinfo->output_height = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_height, 2L); cinfo->min_DCT_scaled_size = 4; } else { // Provide 1/1 scaling cinfo->output_width = cinfo->image_width; cinfo->output_height = cinfo->image_height; cinfo->min_DCT_scaled_size = DCTSIZE; } // In selecting the actual DCT scaling for each component, we try to // * scale up the chroma components via IDCT scaling rather than upsampling. // * This saves time if the upsampler gets to use 1:1 scaling. // * Note this code assumes that the supported DCT scalings are powers of 2. for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) { int ssize = cinfo->min_DCT_scaled_size; while (ssize < DCTSIZE && (compptr->h_samp_factor * ssize * 2 <= cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) && (compptr->v_samp_factor * ssize * 2 <= cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size)) { ssize = ssize * 2; } compptr->DCT_scaled_size = ssize; } // Recompute downsampled dimensions of components; // * application needs to know these if using raw downsampled data. for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) { // Size in samples, after IDCT scaling compptr->downsampled_width = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_width * (LONG) (compptr->h_samp_factor * compptr->DCT_scaled_size), (LONG) (cinfo->max_h_samp_factor * DCTSIZE)); compptr->downsampled_height = (JDIMENSION) jdiv_round_up((LONG) cinfo->image_height * (LONG) (compptr->v_samp_factor * compptr->DCT_scaled_size), (LONG) (cinfo->max_v_samp_factor * DCTSIZE)); } #else // !IDCT_SCALING_SUPPORTED // Hardwire it to "no scaling" cinfo->output_width = cinfo->image_width; cinfo->output_height = cinfo->image_height; // jdinput.c has already initialized DCT_scaled_size to DCTSIZE, // * and has computed unscaled downsampled_width and downsampled_height. #endif // IDCT_SCALING_SUPPORTED // Report number of components in selected colorspace. // Probably this should be in the color conversion module... switch (cinfo->out_color_space) { case JCS_GRAYSCALE: cinfo->out_color_components = 1; break; case JCS_RGB: #if RGB_PIXELSIZE != 3 cinfo->out_color_components = RGB_PIXELSIZE; break; #endif // else share code with YCbCr case JCS_YCbCr: cinfo->out_color_components = 3; break; case JCS_CMYK: case JCS_YCCK: cinfo->out_color_components = 4; break; default: // else must be same colorspace as in file cinfo->out_color_components = cinfo->num_components; break; } cinfo->output_components = (cinfo->quantize_colors ? 1 : cinfo->out_color_components); // See if upsampler will want to emit more than one row at a time if (use_merged_upsample(cinfo)) cinfo->rec_outbuf_height = cinfo->max_v_samp_factor; else cinfo->rec_outbuf_height = 1; } // * Several decompression processes need to range-limit values to the range // * 0..MAXJSAMPLE; the input value may fall somewhat outside this range // * due to noise introduced by quantization, roundoff error, etc. These // * processes are inner loops and need to be as fast as possible. On most // * machines, particularly CPUs with pipelines or instruction prefetch, // * a (subscript-check-less) C table lookup // * x = sample_range_limit[x]; // * is faster than explicit tests // * if (x < 0) x = 0; // * else if (x > MAXJSAMPLE) x = MAXJSAMPLE; // * These processes all use a common table prepared by the routine below. // * // * For most steps we can mathematically guarantee that the initial value // * of x is within MAXJSAMPLE+1 of the legal range, so a table running from // * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial // * limiting step (just after the IDCT), a wildly out-of-range value is // * possible if the input data is corrupt. To avoid any chance of indexing // * off the end of memory and getting a bad-pointer trap, we perform the // * post-IDCT limiting thus: // * x = range_limit[x & MASK]; // * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit // * samples. Under normal circumstances this is more than enough range and // * a correct output will be generated; with bogus input data the mask will // * cause wraparound, and we will safely generate a bogus-but-in-range output. // * For the post-IDCT step, we want to convert the data from signed to unsigned // * representation by adding CENTERJSAMPLE at the same time that we limit it. // * So the post-IDCT limiting table ends up looking like this: // * CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE, // * MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), // * 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), // * 0,1,...,CENTERJSAMPLE-1 // * Negative inputs select values from the upper half of the table after // * masking. // * // * We can save some space by overlapping the start of the post-IDCT table // * with the simpler range limiting table. The post-IDCT table begins at // * sample_range_limit + CENTERJSAMPLE. // * // * Note that the table is allocated in near data space on PCs; it's small // * enough and used often enough to justify this. LOCAL void prepare_range_limit_table (j_decompress_ptr cinfo) // Allocate and fill in the sample_range_limit table { JSAMPLE * table; int i; table = (JSAMPLE *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE)); table += (MAXJSAMPLE+1); // allow negative subscripts of simple table cinfo->sample_range_limit = table; // First segment of "simple" table: limit[x] = 0 for x < 0 MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE)); // Main part of "simple" table: limit[x] = x for (i = 0; i <= MAXJSAMPLE; i++) table[i] = (JSAMPLE) i; table += CENTERJSAMPLE; // Point to where post-IDCT table starts // End of simple table, rest of first half of post-IDCT table for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++) table[i] = MAXJSAMPLE; // Second half of post-IDCT table MEMZERO(table + (2 * (MAXJSAMPLE+1)), (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE)); MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE), cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE)); } // * Master selection of decompression modules. // * This is done once at jpeg_start_decompress time. We determine // * which modules will be used and give them appropriate initialization calls. // * We also initialize the decompressor input side to begin consuming data. // * // * Since jpeg_read_header has finished, we know what is in the SOF // * and (first) SOS markers. We also have all the application parameter // * settings. LOCAL void master_selection (j_decompress_ptr cinfo) { my_master_ptr master = (my_master_ptr) cinfo->master; boolean use_c_buffer; LONG samplesperrow; JDIMENSION jd_samplesperrow; // Initialize dimensions and other stuff jpeg_calc_output_dimensions(cinfo); prepare_range_limit_table(cinfo); // Width of an output scanline must be representable as JDIMENSION. samplesperrow = (LONG) cinfo->output_width * (LONG) cinfo->out_color_components; jd_samplesperrow = (JDIMENSION) samplesperrow; if ((LONG) jd_samplesperrow != samplesperrow) ERREXIT(cinfo, JERR_WIDTH_OVERFLOW); // Initialize my private state master->pass_number = 0; master->using_merged_upsample = use_merged_upsample(cinfo); // Color quantizer selection master->quantizer_1pass = NULL; master->quantizer_2pass = NULL; // No mode changes if not using buffered-image mode. if (! cinfo->quantize_colors || ! cinfo->buffered_image) { cinfo->enable_1pass_quant = FALSE; cinfo->enable_external_quant = FALSE; cinfo->enable_2pass_quant = FALSE; } if (cinfo->quantize_colors) { if (cinfo->raw_data_out) ERREXIT(cinfo, JERR_NOTIMPL); // 2-pass quantizer only works in 3-component color space. if (cinfo->out_color_components != 3) { cinfo->enable_1pass_quant = TRUE; cinfo->enable_external_quant = FALSE; cinfo->enable_2pass_quant = FALSE; cinfo->colormap = NULL; } else if (cinfo->colormap != NULL) { cinfo->enable_external_quant = TRUE; } else if (cinfo->two_pass_quantize) { cinfo->enable_2pass_quant = TRUE; } else { cinfo->enable_1pass_quant = TRUE; } if (cinfo->enable_1pass_quant) { #ifdef QUANT_1PASS_SUPPORTED jinit_1pass_quantizer(cinfo); master->quantizer_1pass = cinfo->cquantize; #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif } // We use the 2-pass code to map to external colormaps. if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) { #ifdef QUANT_2PASS_SUPPORTED jinit_2pass_quantizer(cinfo); master->quantizer_2pass = cinfo->cquantize; #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif } // If both quantizers are initialized, the 2-pass one is left active; // * this is necessary for starting with quantization to an external map. } // Post-processing: in particular, color conversion first if (! cinfo->raw_data_out) { if (master->using_merged_upsample) { #ifdef UPSAMPLE_MERGING_SUPPORTED jinit_merged_upsampler(cinfo); // does color conversion too #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif } else { jinit_color_deconverter(cinfo); jinit_upsampler(cinfo); } jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant); } // Inverse DCT jinit_inverse_dct(cinfo); // Entropy decoding: either Huffman or arithmetic coding. if (cinfo->arith_code) { ERREXIT(cinfo, JERR_ARITH_NOTIMPL); } else { if (cinfo->progressive_mode) { #ifdef D_PROGRESSIVE_SUPPORTED jinit_phuff_decoder(cinfo); #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif } else jinit_huff_decoder(cinfo); } // Initialize principal buffer controllers. use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image; jinit_d_coef_controller(cinfo, use_c_buffer); if (! cinfo->raw_data_out) jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */); // We can now tell the memory manager to allocate virtual arrays. (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo); // Initialize input side of decompressor to consume first scan. (*cinfo->inputctl->start_input_pass) (cinfo); #ifdef D_MULTISCAN_FILES_SUPPORTED // If jpeg_start_decompress will read the whole file, initialize // * progress monitoring appropriately. The input step is counted // * as one pass. if (cinfo->progress != NULL && ! cinfo->buffered_image && cinfo->inputctl->has_multiple_scans) { int nscans; // Estimate number of scans to set pass_limit. if (cinfo->progressive_mode) { // Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. nscans = 2 + 3 * cinfo->num_components; } else { // For a nonprogressive multiscan file, estimate 1 scan per component. nscans = cinfo->num_components; } cinfo->progress->pass_counter = 0L; cinfo->progress->pass_limit = (LONG) cinfo->total_iMCU_rows * nscans; cinfo->progress->completed_passes = 0; cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2); // Count the input pass as done master->pass_number++; } #endif // D_MULTISCAN_FILES_SUPPORTED } // * Per-pass setup. // * This is called at the beginning of each output pass. We determine which // * modules will be active during this pass and give them appropriate // * start_pass calls. We also set is_dummy_pass to indicate whether this // * is a "real" output pass or a dummy pass for color quantization. // * (In the latter case, jdapi.c will crank the pass to completion.) METHODDEF void prepare_for_output_pass (j_decompress_ptr cinfo) { my_master_ptr master = (my_master_ptr) cinfo->master; if (master->pub.is_dummy_pass) { #ifdef QUANT_2PASS_SUPPORTED // Final pass of 2-pass quantization master->pub.is_dummy_pass = FALSE; (*cinfo->cquantize->start_pass) (cinfo, FALSE); (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST); (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST); #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif // QUANT_2PASS_SUPPORTED } else { if (cinfo->quantize_colors && cinfo->colormap == NULL) { // Select new quantization method if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) { cinfo->cquantize = master->quantizer_2pass; master->pub.is_dummy_pass = TRUE; } else if (cinfo->enable_1pass_quant) { cinfo->cquantize = master->quantizer_1pass; } else { ERREXIT(cinfo, JERR_MODE_CHANGE); } } (*cinfo->idct->start_pass) (cinfo); (*cinfo->coef->start_output_pass) (cinfo); if (! cinfo->raw_data_out) { if (! master->using_merged_upsample) (*cinfo->cconvert->start_pass) (cinfo); (*cinfo->upsample->start_pass) (cinfo); if (cinfo->quantize_colors) (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass); (*cinfo->post->start_pass) (cinfo, (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU)); (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU); } } // Set up progress monitor's pass info if present if (cinfo->progress != NULL) { cinfo->progress->completed_passes = master->pass_number; cinfo->progress->total_passes = master->pass_number + (master->pub.is_dummy_pass ? 2 : 1); // In buffered-image mode, we assume one more output pass if EOI not // * yet reached, but no more passes if EOI has been reached. if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) { cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1); } } } // * Finish up at end of an output pass. METHODDEF void finish_output_pass (j_decompress_ptr cinfo) { my_master_ptr master = (my_master_ptr) cinfo->master; if (cinfo->quantize_colors) (*cinfo->cquantize->finish_pass) (cinfo); master->pass_number++; } #ifdef D_MULTISCAN_FILES_SUPPORTED // * Switch to a new external colormap between output passes. GLOBAL void jpeg_new_colormap (j_decompress_ptr cinfo) { my_master_ptr master = (my_master_ptr) cinfo->master; // Prevent application from calling me at wrong times if (cinfo->global_state != DSTATE_BUFIMAGE) ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); if (cinfo->quantize_colors && cinfo->enable_external_quant && cinfo->colormap != NULL) { // Select 2-pass quantizer for external colormap use cinfo->cquantize = master->quantizer_2pass; // Notify quantizer of colormap change (*cinfo->cquantize->new_color_map) (cinfo); master->pub.is_dummy_pass = FALSE; // just in case } else ERREXIT(cinfo, JERR_MODE_CHANGE); } #endif // D_MULTISCAN_FILES_SUPPORTED // * Initialize master decompression control and select active modules. // * This is performed at the start of jpeg_start_decompress. GLOBAL void jinit_master_decompress (j_decompress_ptr cinfo) { my_master_ptr master; master = (my_master_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_decomp_master)); cinfo->master = (struct jpeg_decomp_master *) master; master->pub.prepare_for_output_pass = prepare_for_output_pass; master->pub.finish_output_pass = finish_output_pass; master->pub.is_dummy_pass = FALSE; master_selection(cinfo); }