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1 line
8.1 KiB
C
1 line
8.1 KiB
C
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/*
* jcapi.c
*
* Copyright (C) 1994, 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 application interface code for the compression half of
* the JPEG library. Most of the routines intended to be called directly by
* an application are in this file. But also see jcparam.c for
* parameter-setup helper routines, and jcomapi.c for routines shared by
* compression and decompression.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
/*
* Initialization of a JPEG compression object.
* The error manager must already be set up (in case memory manager fails).
*/
GLOBAL void
jpeg_create_compress (j_compress_ptr cinfo)
{
int i;
/* For debugging purposes, zero the whole master structure.
* But error manager pointer is already there, so save and restore it.
*/
{
struct jpeg_error_mgr * err = cinfo->err;
MEMZERO(cinfo, SIZEOF(struct jpeg_compress_struct));
cinfo->err = err;
}
cinfo->is_decompressor = FALSE;
/* Initialize a memory manager instance for this object */
jinit_memory_mgr((j_common_ptr) cinfo);
/* Zero out pointers to permanent structures. */
cinfo->progress = NULL;
cinfo->dest = NULL;
cinfo->comp_info = NULL;
for (i = 0; i < NUM_QUANT_TBLS; i++)
cinfo->quant_tbl_ptrs[i] = NULL;
for (i = 0; i < NUM_HUFF_TBLS; i++) {
cinfo->dc_huff_tbl_ptrs[i] = NULL;
cinfo->ac_huff_tbl_ptrs[i] = NULL;
}
cinfo->input_gamma = 1.0; /* in case application forgets */
/* OK, I'm ready */
cinfo->global_state = CSTATE_START;
}
/*
* Destruction of a JPEG compression object
*/
GLOBAL void
jpeg_destroy_compress (j_compress_ptr cinfo)
{
jpeg_destroy((j_common_ptr) cinfo); /* use common routine */
}
/*
* Forcibly suppress or un-suppress all quantization and Huffman tables.
* Marks all currently defined tables as already written (if suppress)
* or not written (if !suppress). This will control whether they get emitted
* by a subsequent jpeg_start_compress call.
*
* This routine is exported for use by applications that want to produce
* abbreviated JPEG datastreams. It logically belongs in jcparam.c, but
* since it is called by jpeg_start_compress, we put it here --- otherwise
* jcparam.o would be linked whether the application used it or not.
*/
GLOBAL void
jpeg_suppress_tables (j_compress_ptr cinfo, boolean suppress)
{
int i;
JQUANT_TBL * qtbl;
JHUFF_TBL * htbl;
for (i = 0; i < NUM_QUANT_TBLS; i++) {
if ((qtbl = cinfo->quant_tbl_ptrs[i]) != NULL)
qtbl->sent_table = suppress;
}
for (i = 0; i < NUM_HUFF_TBLS; i++) {
if ((htbl = cinfo->dc_huff_tbl_ptrs[i]) != NULL)
htbl->sent_table = suppress;
if ((htbl = cinfo->ac_huff_tbl_ptrs[i]) != NULL)
htbl->sent_table = suppress;
}
}
/*
* Compression initialization.
* Before calling this, all parameters and a data destination must be set up.
*
* We require a write_all_tables parameter as a failsafe check when writing
* multiple datastreams from the same compression object. Since prior runs
* will have left all the tables marked sent_table=TRUE, a subsequent run
* would emit an abbreviated stream (no tables) by default. This may be what
* is wanted, but for safety's sake it should not be the default behavior:
* programmers should have to make a deliberate choice to emit abbreviated
* images. Therefore the documentation and examples should encourage people
* to pass write_all_tables=TRUE; then it will take active thought to do the
* wrong thing.
*/
GLOBAL void
jpeg_start_compress (j_compress_ptr cinfo, boolean write_all_tables)
{
if (cinfo->global_state != CSTATE_START)
ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
if (write_all_tables)
jpeg_suppress_tables(cinfo, FALSE); /* mark all tables to be written */
/* (Re)initialize error mgr and destination modules */
(*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
(*cinfo->dest->init_destination) (cinfo);
/* Perform
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