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