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