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1 /*
2  * jcapistd.c
3  *
4  * Copyright (C) 1994-1996, Thomas G. Lane.
5  * This file is part of the Independent JPEG Group's software.
6  * For conditions of distribution and use, see the accompanying README.ijg
7  * file.
8  *
9  * This file contains application interface code for the compression half
10  * of the JPEG library.  These are the "standard" API routines that are
11  * used in the normal full-compression case.  They are not used by a
12  * transcoding-only application.  Note that if an application links in
13  * jpeg_start_compress, it will end up linking in the entire compressor.
14  * We thus must separate this file from jcapimin.c to avoid linking the
15  * whole compression library into a transcoder.
16  */
17 
18 #define JPEG_INTERNALS
19 #include "jinclude.h"
20 #include "jpeglib.h"
21 
22 
23 /*
24  * Compression initialization.
25  * Before calling this, all parameters and a data destination must be set up.
26  *
27  * We require a write_all_tables parameter as a failsafe check when writing
28  * multiple datastreams from the same compression object.  Since prior runs
29  * will have left all the tables marked sent_table=TRUE, a subsequent run
30  * would emit an abbreviated stream (no tables) by default.  This may be what
31  * is wanted, but for safety's sake it should not be the default behavior:
32  * programmers should have to make a deliberate choice to emit abbreviated
33  * images.  Therefore the documentation and examples should encourage people
34  * to pass write_all_tables=TRUE; then it will take active thought to do the
35  * wrong thing.
36  */
37 
38 GLOBAL(void)
jpeg_start_compress(j_compress_ptr cinfo,boolean write_all_tables)39 jpeg_start_compress(j_compress_ptr cinfo, boolean write_all_tables)
40 {
41   if (cinfo->global_state != CSTATE_START)
42     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
43 
44   if (write_all_tables)
45     jpeg_suppress_tables(cinfo, FALSE); /* mark all tables to be written */
46 
47   /* (Re)initialize error mgr and destination modules */
48   (*cinfo->err->reset_error_mgr) ((j_common_ptr)cinfo);
49   (*cinfo->dest->init_destination) (cinfo);
50   /* Perform master selection of active modules */
51   jinit_compress_master(cinfo);
52   /* Set up for the first pass */
53   (*cinfo->master->prepare_for_pass) (cinfo);
54   /* Ready for application to drive first pass through jpeg_write_scanlines
55    * or jpeg_write_raw_data.
56    */
57   cinfo->next_scanline = 0;
58   cinfo->global_state = (cinfo->raw_data_in ? CSTATE_RAW_OK : CSTATE_SCANNING);
59 }
60 
61 
62 /*
63  * Write some scanlines of data to the JPEG compressor.
64  *
65  * The return value will be the number of lines actually written.
66  * This should be less than the supplied num_lines only in case that
67  * the data destination module has requested suspension of the compressor,
68  * or if more than image_height scanlines are passed in.
69  *
70  * Note: we warn about excess calls to jpeg_write_scanlines() since
71  * this likely signals an application programmer error.  However,
72  * excess scanlines passed in the last valid call are *silently* ignored,
73  * so that the application need not adjust num_lines for end-of-image
74  * when using a multiple-scanline buffer.
75  */
76 
77 GLOBAL(JDIMENSION)
jpeg_write_scanlines(j_compress_ptr cinfo,JSAMPARRAY scanlines,JDIMENSION num_lines)78 jpeg_write_scanlines(j_compress_ptr cinfo, JSAMPARRAY scanlines,
79                      JDIMENSION num_lines)
80 {
81   JDIMENSION row_ctr, rows_left;
82 
83   if (cinfo->global_state != CSTATE_SCANNING)
84     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
85   if (cinfo->next_scanline >= cinfo->image_height)
86     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
87 
88   /* Call progress monitor hook if present */
89   if (cinfo->progress != NULL) {
90     cinfo->progress->pass_counter = (long)cinfo->next_scanline;
91     cinfo->progress->pass_limit = (long)cinfo->image_height;
92     (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
93   }
94 
95   /* Give master control module another chance if this is first call to
96    * jpeg_write_scanlines.  This lets output of the frame/scan headers be
97    * delayed so that application can write COM, etc, markers between
98    * jpeg_start_compress and jpeg_write_scanlines.
99    */
100   if (cinfo->master->call_pass_startup)
101     (*cinfo->master->pass_startup) (cinfo);
102 
103   /* Ignore any extra scanlines at bottom of image. */
104   rows_left = cinfo->image_height - cinfo->next_scanline;
105   if (num_lines > rows_left)
106     num_lines = rows_left;
107 
108   row_ctr = 0;
109   (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, num_lines);
110   cinfo->next_scanline += row_ctr;
111   return row_ctr;
112 }
113 
114 
115 /*
116  * Alternate entry point to write raw data.
117  * Processes exactly one iMCU row per call, unless suspended.
118  */
119 
120 GLOBAL(JDIMENSION)
jpeg_write_raw_data(j_compress_ptr cinfo,JSAMPIMAGE data,JDIMENSION num_lines)121 jpeg_write_raw_data(j_compress_ptr cinfo, JSAMPIMAGE data,
122                     JDIMENSION num_lines)
123 {
124   JDIMENSION lines_per_iMCU_row;
125 
126   if (cinfo->global_state != CSTATE_RAW_OK)
127     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
128   if (cinfo->next_scanline >= cinfo->image_height) {
129     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
130     return 0;
131   }
132 
133   /* Call progress monitor hook if present */
134   if (cinfo->progress != NULL) {
135     cinfo->progress->pass_counter = (long)cinfo->next_scanline;
136     cinfo->progress->pass_limit = (long)cinfo->image_height;
137     (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
138   }
139 
140   /* Give master control module another chance if this is first call to
141    * jpeg_write_raw_data.  This lets output of the frame/scan headers be
142    * delayed so that application can write COM, etc, markers between
143    * jpeg_start_compress and jpeg_write_raw_data.
144    */
145   if (cinfo->master->call_pass_startup)
146     (*cinfo->master->pass_startup) (cinfo);
147 
148   /* Verify that at least one iMCU row has been passed. */
149   lines_per_iMCU_row = cinfo->max_v_samp_factor * DCTSIZE;
150   if (num_lines < lines_per_iMCU_row)
151     ERREXIT(cinfo, JERR_BUFFER_SIZE);
152 
153   /* Directly compress the row. */
154   if (!(*cinfo->coef->compress_data) (cinfo, data)) {
155     /* If compressor did not consume the whole row, suspend processing. */
156     return 0;
157   }
158 
159   /* OK, we processed one iMCU row. */
160   cinfo->next_scanline += lines_per_iMCU_row;
161   return lines_per_iMCU_row;
162 }
163