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