| /* | |
| * jdtrans.c | |
| * | |
| * Copyright (C) 1995-1997, Thomas G. Lane. | |
| * Modified 2000-2009 by Guido Vollbeding. | |
| * 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 library routines for transcoding decompression, | |
| * that is, reading raw DCT coefficient arrays from an input JPEG file. | |
| * The routines in jdapimin.c will also be needed by a transcoder. | |
| */ | |
| /* Forward declarations */ | |
| LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo)); | |
| /* | |
| * Read the coefficient arrays from a JPEG file. | |
| * jpeg_read_header must be completed before calling this. | |
| * | |
| * The entire image is read into a set of virtual coefficient-block arrays, | |
| * one per component. The return value is a pointer to the array of | |
| * virtual-array descriptors. These can be manipulated directly via the | |
| * JPEG memory manager, or handed off to jpeg_write_coefficients(). | |
| * To release the memory occupied by the virtual arrays, call | |
| * jpeg_finish_decompress() when done with the data. | |
| * | |
| * An alternative usage is to simply obtain access to the coefficient arrays | |
| * during a buffered-image-mode decompression operation. This is allowed | |
| * after any jpeg_finish_output() call. The arrays can be accessed until | |
| * jpeg_finish_decompress() is called. (Note that any call to the library | |
| * may reposition the arrays, so don't rely on access_virt_barray() results | |
| * to stay valid across library calls.) | |
| * | |
| * Returns NULL if suspended. This case need be checked only if | |
| * a suspending data source is used. | |
| */ | |
| GLOBAL(jvirt_barray_ptr *) | |
| jpeg_read_coefficients (j_decompress_ptr cinfo) | |
| { | |
| if (cinfo->global_state == DSTATE_READY) { | |
| /* First call: initialize active modules */ | |
| transdecode_master_selection(cinfo); | |
| cinfo->global_state = DSTATE_RDCOEFS; | |
| } | |
| if (cinfo->global_state == DSTATE_RDCOEFS) { | |
| /* Absorb whole file into the coef buffer */ | |
| for (;;) { | |
| int retcode; | |
| /* Call progress monitor hook if present */ | |
| if (cinfo->progress != NULL) | |
| (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); | |
| /* Absorb some more input */ | |
| retcode = (*cinfo->inputctl->consume_input) (cinfo); | |
| if (retcode == JPEG_SUSPENDED) | |
| return NULL; | |
| if (retcode == JPEG_REACHED_EOI) | |
| break; | |
| /* Advance progress counter if appropriate */ | |
| if (cinfo->progress != NULL && | |
| (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { | |
| if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { | |
| /* startup underestimated number of scans; ratchet up one scan */ | |
| cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows; | |
| } | |
| } | |
| } | |
| /* Set state so that jpeg_finish_decompress does the right thing */ | |
| cinfo->global_state = DSTATE_STOPPING; | |
| } | |
| /* At this point we should be in state DSTATE_STOPPING if being used | |
| * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access | |
| * to the coefficients during a full buffered-image-mode decompression. | |
| */ | |
| if ((cinfo->global_state == DSTATE_STOPPING || | |
| cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) { | |
| return cinfo->coef->coef_arrays; | |
| } | |
| /* Oops, improper usage */ | |
| ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); | |
| return NULL; /* keep compiler happy */ | |
| } | |
| /* | |
| * Master selection of decompression modules for transcoding. | |
| * This substitutes for jdmaster.c's initialization of the full decompressor. | |
| */ | |
| LOCAL(void) | |
| transdecode_master_selection (j_decompress_ptr cinfo) | |
| { | |
| /* This is effectively a buffered-image operation. */ | |
| cinfo->buffered_image = TRUE; | |
| /* Compute output image dimensions and related values. */ | |
| jpeg_core_output_dimensions(cinfo); | |
| /* Entropy decoding: either Huffman or arithmetic coding. */ | |
| if (cinfo->arith_code) | |
| jinit_arith_decoder(cinfo); | |
| else { | |
| jinit_huff_decoder(cinfo); | |
| } | |
| /* Always get a full-image coefficient buffer. */ | |
| jinit_d_coef_controller(cinfo, TRUE); | |
| /* 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); | |
| /* Initialize progress monitoring. */ | |
| if (cinfo->progress != NULL) { | |
| 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 if (cinfo->inputctl->has_multiple_scans) { | |
| /* For a nonprogressive multiscan file, estimate 1 scan per component. */ | |
| nscans = cinfo->num_components; | |
| } else { | |
| nscans = 1; | |
| } | |
| cinfo->progress->pass_counter = 0L; | |
| cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans; | |
| cinfo->progress->completed_passes = 0; | |
| cinfo->progress->total_passes = 1; | |
| } | |
| } | |