1 /*
2 * jdcoefct.h
3 *
4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1994-1997, Thomas G. Lane.
6 * libjpeg-turbo Modifications:
7 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
8 * Copyright (C) 2020, Google, Inc.
9 * For conditions of distribution and use, see the accompanying README.ijg
10 * file.
11 */
12
13 #define JPEG_INTERNALS
14 #include "jpeglib.h"
15
16
17 /* Block smoothing is only applicable for progressive JPEG, so: */
18 #ifndef D_PROGRESSIVE_SUPPORTED
19 #undef BLOCK_SMOOTHING_SUPPORTED
20 #endif
21
22
23 /* Private buffer controller object */
24
25 typedef struct {
26 struct jpeg_d_coef_controller pub; /* public fields */
27
28 /* These variables keep track of the current location of the input side. */
29 /* cinfo->input_iMCU_row is also used for this. */
30 JDIMENSION MCU_ctr; /* counts MCUs processed in current row */
31 int MCU_vert_offset; /* counts MCU rows within iMCU row */
32 int MCU_rows_per_iMCU_row; /* number of such rows needed */
33
34 /* The output side's location is represented by cinfo->output_iMCU_row. */
35
36 /* In single-pass modes, it's sufficient to buffer just one MCU.
37 * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
38 * and let the entropy decoder write into that workspace each time.
39 * In multi-pass modes, this array points to the current MCU's blocks
40 * within the virtual arrays; it is used only by the input side.
41 */
42 JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
43
44 /* Temporary workspace for one MCU */
45 JCOEF *workspace;
46
47 #ifdef D_MULTISCAN_FILES_SUPPORTED
48 /* In multi-pass modes, we need a virtual block array for each component. */
49 jvirt_barray_ptr whole_image[MAX_COMPONENTS];
50 #endif
51
52 #ifdef BLOCK_SMOOTHING_SUPPORTED
53 /* When doing block smoothing, we latch coefficient Al values here */
54 int *coef_bits_latch;
55 #define SAVED_COEFS 10 /* we save coef_bits[0..9] */
56 #endif
57 } my_coef_controller;
58
59 typedef my_coef_controller *my_coef_ptr;
60
61
62 LOCAL(void)
start_iMCU_row(j_decompress_ptr cinfo)63 start_iMCU_row(j_decompress_ptr cinfo)
64 /* Reset within-iMCU-row counters for a new row (input side) */
65 {
66 my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
67
68 /* In an interleaved scan, an MCU row is the same as an iMCU row.
69 * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
70 * But at the bottom of the image, process only what's left.
71 */
72 if (cinfo->comps_in_scan > 1) {
73 coef->MCU_rows_per_iMCU_row = 1;
74 } else {
75 if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows - 1))
76 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
77 else
78 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
79 }
80
81 coef->MCU_ctr = 0;
82 coef->MCU_vert_offset = 0;
83 }
84