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1 line
11 KiB
C
1 line
11 KiB
C
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/*
* jdapi.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 decompression half of
* the JPEG library. Most of the routines intended to be called directly by
* an application are in this file. But also see jcomapi.c for routines
* shared by compression and decompression.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
/*
* Initialization of a JPEG decompression object.
* The error manager must already be set up (in case memory manager fails).
*/
GLOBAL void
jpeg_create_decompress (j_decompress_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_decompress_struct));
cinfo->err = err;
}
cinfo->is_decompressor = TRUE;
/* 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->src = 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->sample_range_limit = NULL;
/* Initialize marker processor so application can override methods
* for COM, APPn markers before calling jpeg_read_header.
*/
cinfo->marker = NULL;
jinit_marker_reader(cinfo);
/* OK, I'm ready */
cinfo->global_state = DSTATE_START;
}
/*
* Destruction of a JPEG decompression object
*/
GLOBAL void
jpeg_destroy_decompress (j_decompress_ptr cinfo)
{
jpeg_destroy((j_common_ptr) cinfo); /* use common routine */
}
/*
* Set default decompression parameters.
*/
LOCAL void
default_decompress_parms (j_decompress_ptr cinfo)
{
/* Guess the input colorspace, and set output colorspace accordingly. */
/* (Wish JPEG committee had provided a real way to specify this...) */
/* Note application may override our guesses. */
switch (cinfo->num_components) {
case 1:
cinfo->jpeg_color_space = JCS_GRAYSCALE;
cinfo->out_color_space = JCS_GRAYSCALE;
break;
case 3:
if (cinfo->saw_JFIF_marker) {
cinfo->jpeg_color_space = JCS_YCbCr; /* JFIF implies YCbCr */
} else if (cinfo->saw_Adobe_marker) {
switch (cinfo->Adobe_transform) {
case 0:
cinfo->jpeg_color_space = JCS_RGB;
break;
case 1:
cinfo->jpeg_color_space = JCS_YCbCr;
break;
default:
WARNMS1(cinfo, JWRN_ADOBE_XFORM, cinfo->Adobe_transform);
cinfo->jpeg_color_space = JCS_YCbCr; /* assume it's YCbCr */
break;
}
} else {
/* Saw no special markers, try to guess from the component IDs */
int cid0 = cinfo->comp_info[0].component_id;
int cid1 = cinfo->comp_info[1].component_id;
int cid2 = cinfo->comp_info[2].component_id;
if (cid0 == 1 && cid1 == 2 && cid2 == 3)
cinfo->jpeg_color_space = JCS_YCbCr; /* assume JFIF w/out marker */
else if (cid0 == 82 && cid1 == 71 && cid2 == 66)
cinfo->jpeg_color_space = JCS_RGB; /* ASCII 'R', 'G', 'B' */
else {
TRACEMS3(cinfo, 1, JTRC_UNKNOWN_IDS, cid0, cid1, cid2);
cinfo->jpeg_color_space = JCS_YCbCr; /* assume it's YCbCr */
}
}
/* Always guess RGB is proper output colorspace. */
cinfo->out_color_space = JCS_RGB;
break;
case 4:
if (cinfo->saw_Adobe_marker) {
switch (cinfo->Adobe_transform) {
case 0:
cinfo->jpeg_color_space = JCS_CMYK;
break;
case 2:
cinfo->jpeg_color_space = JCS_YCCK;
break;
default:
WARNMS1(cinfo, JWRN_ADOBE_XFORM, cinfo->Adobe_transform);
cinfo->jpeg_color_space = JCS_YCCK; /* assume it's YCCK */
break;
}
} else {
/* No special markers, assume straight CMYK. */
cinfo->jpeg_color_space = JCS_CMYK;
}
cinfo->out_color_space = JCS_CM
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