1 /* 2 * jdtrans.c 3 * 4 * Copyright (C) 1995-1997, Thomas G. Lane. 5 * Modified 2000-2009 by Guido Vollbeding. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains library routines for transcoding decompression, 10 * that is, reading raw DCT coefficient arrays from an input JPEG file. 11 * The routines in jdapimin.c will also be needed by a transcoder. 12 */ 13 14 #define JPEG_INTERNALS 15 #include "jinclude.h" 16 #include "jpeglib.h" 17 18 19 /* Forward declarations */ 20 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo)); 21 22 23 /* 24 * Read the coefficient arrays from a JPEG file. 25 * jpeg_read_header must be completed before calling this. 26 * 27 * The entire image is read into a set of virtual coefficient-block arrays, 28 * one per component. The return value is a pointer to the array of 29 * virtual-array descriptors. These can be manipulated directly via the 30 * JPEG memory manager, or handed off to jpeg_write_coefficients(). 31 * To release the memory occupied by the virtual arrays, call 32 * jpeg_finish_decompress() when done with the data. 33 * 34 * An alternative usage is to simply obtain access to the coefficient arrays 35 * during a buffered-image-mode decompression operation. This is allowed 36 * after any jpeg_finish_output() call. The arrays can be accessed until 37 * jpeg_finish_decompress() is called. (Note that any call to the library 38 * may reposition the arrays, so don't rely on access_virt_barray() results 39 * to stay valid across library calls.) 40 * 41 * Returns NULL if suspended. This case need be checked only if 42 * a suspending data source is used. 43 */ 44 45 GLOBAL(jvirt_barray_ptr *) 46 jpeg_read_coefficients (j_decompress_ptr cinfo) 47 { 48 if (cinfo->global_state == DSTATE_READY) { 49 /* First call: initialize active modules */ 50 transdecode_master_selection(cinfo); 51 cinfo->global_state = DSTATE_RDCOEFS; 52 } 53 if (cinfo->global_state == DSTATE_RDCOEFS) { 54 /* Absorb whole file into the coef buffer */ 55 for (;;) { 56 int retcode; 57 /* Call progress monitor hook if present */ 58 if (cinfo->progress != NULL) 59 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 60 /* Absorb some more input */ 61 retcode = (*cinfo->inputctl->consume_input) (cinfo); 62 if (retcode == JPEG_SUSPENDED) 63 return NULL; 64 if (retcode == JPEG_REACHED_EOI) 65 break; 66 /* Advance progress counter if appropriate */ 67 if (cinfo->progress != NULL && 68 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { 69 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { 70 /* startup underestimated number of scans; ratchet up one scan */ 71 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows; 72 } 73 } 74 } 75 /* Set state so that jpeg_finish_decompress does the right thing */ 76 cinfo->global_state = DSTATE_STOPPING; 77 } 78 /* At this point we should be in state DSTATE_STOPPING if being used 79 * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access 80 * to the coefficients during a full buffered-image-mode decompression. 81 */ 82 if ((cinfo->global_state == DSTATE_STOPPING || 83 cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) { 84 return cinfo->coef->coef_arrays; 85 } 86 /* Oops, improper usage */ 87 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 88 return NULL; /* keep compiler happy */ 89 } 90 91 92 /* 93 * Master selection of decompression modules for transcoding. 94 * This substitutes for jdmaster.c's initialization of the full decompressor. 95 */ 96 97 LOCAL(void) 98 transdecode_master_selection (j_decompress_ptr cinfo) 99 { 100 /* This is effectively a buffered-image operation. */ 101 cinfo->buffered_image = TRUE; 102 103 /* Compute output image dimensions and related values. */ 104 jpeg_core_output_dimensions(cinfo); 105 106 /* Entropy decoding: either Huffman or arithmetic coding. */ 107 if (cinfo->arith_code) 108 jinit_arith_decoder(cinfo); 109 else { 110 jinit_huff_decoder(cinfo); 111 } 112 113 /* Always get a full-image coefficient buffer. */ 114 jinit_d_coef_controller(cinfo, TRUE); 115 116 /* We can now tell the memory manager to allocate virtual arrays. */ 117 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo); 118 119 /* Initialize input side of decompressor to consume first scan. */ 120 (*cinfo->inputctl->start_input_pass) (cinfo); 121 122 /* Initialize progress monitoring. */ 123 if (cinfo->progress != NULL) { 124 int nscans; 125 /* Estimate number of scans to set pass_limit. */ 126 if (cinfo->progressive_mode) { 127 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */ 128 nscans = 2 + 3 * cinfo->num_components; 129 } else if (cinfo->inputctl->has_multiple_scans) { 130 /* For a nonprogressive multiscan file, estimate 1 scan per component. */ 131 nscans = cinfo->num_components; 132 } else { 133 nscans = 1; 134 } 135 cinfo->progress->pass_counter = 0L; 136 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans; 137 cinfo->progress->completed_passes = 0; 138 cinfo->progress->total_passes = 1; 139 } 140 } 141
