jdtrans.c (5624B)
1 /* 2 * jdtrans.c 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1995-1997, Thomas G. Lane. 6 * libjpeg-turbo Modifications: 7 * Copyright (C) 2020, 2022, D. R. Commander. 8 * For conditions of distribution and use, see the accompanying README.ijg 9 * file. 10 * 11 * This file contains library routines for transcoding decompression, 12 * that is, reading raw DCT coefficient arrays from an input JPEG file. 13 * The routines in jdapimin.c will also be needed by a transcoder. 14 */ 15 16 #define JPEG_INTERNALS 17 #include "jinclude.h" 18 #include "jpeglib.h" 19 #include "jpegapicomp.h" 20 21 22 /* Forward declarations */ 23 LOCAL(void) transdecode_master_selection(j_decompress_ptr cinfo); 24 25 26 /* 27 * Read the coefficient arrays from a JPEG file. 28 * jpeg_read_header must be completed before calling this. 29 * 30 * The entire image is read into a set of virtual coefficient-block arrays, 31 * one per component. The return value is a pointer to the array of 32 * virtual-array descriptors. These can be manipulated directly via the 33 * JPEG memory manager, or handed off to jpeg_write_coefficients(). 34 * To release the memory occupied by the virtual arrays, call 35 * jpeg_finish_decompress() when done with the data. 36 * 37 * An alternative usage is to simply obtain access to the coefficient arrays 38 * during a buffered-image-mode decompression operation. This is allowed 39 * after any jpeg_finish_output() call. The arrays can be accessed until 40 * jpeg_finish_decompress() is called. (Note that any call to the library 41 * may reposition the arrays, so don't rely on access_virt_barray() results 42 * to stay valid across library calls.) 43 * 44 * Returns NULL if suspended. This case need be checked only if 45 * a suspending data source is used. 46 */ 47 48 GLOBAL(jvirt_barray_ptr *) 49 jpeg_read_coefficients(j_decompress_ptr cinfo) 50 { 51 if (cinfo->master->lossless) 52 ERREXIT(cinfo, JERR_NOTIMPL); 53 54 if (cinfo->global_state == DSTATE_READY) { 55 /* First call: initialize active modules */ 56 transdecode_master_selection(cinfo); 57 cinfo->global_state = DSTATE_RDCOEFS; 58 } 59 if (cinfo->global_state == DSTATE_RDCOEFS) { 60 /* Absorb whole file into the coef buffer */ 61 for (;;) { 62 int retcode; 63 /* Call progress monitor hook if present */ 64 if (cinfo->progress != NULL) 65 (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); 66 /* Absorb some more input */ 67 retcode = (*cinfo->inputctl->consume_input) (cinfo); 68 if (retcode == JPEG_SUSPENDED) 69 return NULL; 70 if (retcode == JPEG_REACHED_EOI) 71 break; 72 /* Advance progress counter if appropriate */ 73 if (cinfo->progress != NULL && 74 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { 75 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { 76 /* startup underestimated number of scans; ratchet up one scan */ 77 cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows; 78 } 79 } 80 } 81 /* Set state so that jpeg_finish_decompress does the right thing */ 82 cinfo->global_state = DSTATE_STOPPING; 83 } 84 /* At this point we should be in state DSTATE_STOPPING if being used 85 * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access 86 * to the coefficients during a full buffered-image-mode decompression. 87 */ 88 if ((cinfo->global_state == DSTATE_STOPPING || 89 cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) { 90 return cinfo->coef->coef_arrays; 91 } 92 /* Oops, improper usage */ 93 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 94 return NULL; /* keep compiler happy */ 95 } 96 97 98 /* 99 * Master selection of decompression modules for transcoding. 100 * This substitutes for jdmaster.c's initialization of the full decompressor. 101 */ 102 103 LOCAL(void) 104 transdecode_master_selection(j_decompress_ptr cinfo) 105 { 106 /* This is effectively a buffered-image operation. */ 107 cinfo->buffered_image = TRUE; 108 109 #if JPEG_LIB_VERSION >= 80 110 /* Compute output image dimensions and related values. */ 111 jpeg_core_output_dimensions(cinfo); 112 #endif 113 114 /* Entropy decoding: either Huffman or arithmetic coding. */ 115 if (cinfo->arith_code) { 116 #ifdef D_ARITH_CODING_SUPPORTED 117 jinit_arith_decoder(cinfo); 118 #else 119 ERREXIT(cinfo, JERR_ARITH_NOTIMPL); 120 #endif 121 } else { 122 if (cinfo->progressive_mode) { 123 #ifdef D_PROGRESSIVE_SUPPORTED 124 jinit_phuff_decoder(cinfo); 125 #else 126 ERREXIT(cinfo, JERR_NOT_COMPILED); 127 #endif 128 } else 129 jinit_huff_decoder(cinfo); 130 } 131 132 /* Always get a full-image coefficient buffer. */ 133 if (cinfo->data_precision == 12) 134 j12init_d_coef_controller(cinfo, TRUE); 135 else 136 jinit_d_coef_controller(cinfo, TRUE); 137 138 /* We can now tell the memory manager to allocate virtual arrays. */ 139 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo); 140 141 /* Initialize input side of decompressor to consume first scan. */ 142 (*cinfo->inputctl->start_input_pass) (cinfo); 143 144 /* Initialize progress monitoring. */ 145 if (cinfo->progress != NULL) { 146 int nscans; 147 /* Estimate number of scans to set pass_limit. */ 148 if (cinfo->progressive_mode) { 149 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */ 150 nscans = 2 + 3 * cinfo->num_components; 151 } else if (cinfo->inputctl->has_multiple_scans) { 152 /* For a nonprogressive multiscan file, estimate 1 scan per component. */ 153 nscans = cinfo->num_components; 154 } else { 155 nscans = 1; 156 } 157 cinfo->progress->pass_counter = 0L; 158 cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans; 159 cinfo->progress->completed_passes = 0; 160 cinfo->progress->total_passes = 1; 161 } 162 }