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