JDTRANS.c
资源名称:Visualhk.rar [点击查看]
上传用户:cjw5120
上传日期:2022-05-11
资源大小:5032k
文件大小:5k
源码类别:
网络截获/分析
开发平台:
Visual C++
- ////////////////////////////////////////////////////////////////////////
- //
- // Note : this file is included as part of the Smaller Animals Software
- // JpegFile package. Though this file has not been modified from it's
- // original IJG 6a form, it is not the responsibility on the Independent
- // JPEG Group to answer questions regarding this code.
- //
- // Any questions you have about this code should be addressed to :
- //
- // CHRISDL@PAGESZ.NET - the distributor of this package.
- //
- // Remember, by including this code in the JpegFile package, Smaller
- // Animals Software assumes all responsibilities for answering questions
- // about it. If we (SA Software) can't answer your questions ourselves, we
- // will direct you to people who can.
- //
- // Thanks, CDL.
- //
- ////////////////////////////////////////////////////////////////////////
- /*
- * jdtrans.c
- *
- * Copyright (C) 1995-1996, Thomas G. Lane.
- * 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.
- */
- #define JPEG_INTERNALS
- #include "jinclude.h"
- #include "jpeglib.h"
- /* 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.
- *
- * 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;
- } else if (cinfo->global_state != DSTATE_RDCOEFS)
- ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
- /* 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;
- return cinfo->coef->coef_arrays;
- }
- /*
- * 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)
- {
- /* Entropy decoding: either Huffman or arithmetic coding. */
- if (cinfo->arith_code) {
- ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
- } else {
- if (cinfo->progressive_mode) {
- #ifdef D_PROGRESSIVE_SUPPORTED
- jinit_phuff_decoder(cinfo);
- #else
- ERREXIT(cinfo, JERR_NOT_COMPILED);
- #endif
- } 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;
- }
- }