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
13 #define JPEG_INTERNALS
17 /* Block smoothing is only applicable for progressive JPEG, so: */
18 #ifndef D_PROGRESSIVE_SUPPORTED
19 #undef BLOCK_SMOOTHING_SUPPORTED
23 /* Private buffer controller object */
26 struct jpeg_d_coef_controller pub
; /* public fields */
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 */
34 /* The output side's location is represented by cinfo->output_iMCU_row. */
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.
42 JBLOCKROW MCU_buffer
[D_MAX_BLOCKS_IN_MCU
];
44 /* Temporary workspace for one MCU */
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
];
52 #ifdef BLOCK_SMOOTHING_SUPPORTED
53 /* When doing block smoothing, we latch coefficient Al values here */
55 #define SAVED_COEFS 10 /* we save coef_bits[0..9] */
59 typedef my_coef_controller
*my_coef_ptr
;
63 start_iMCU_row(j_decompress_ptr cinfo
)
64 /* Reset within-iMCU-row counters for a new row (input side) */
66 my_coef_ptr coef
= (my_coef_ptr
)cinfo
->coef
;
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.
72 if (cinfo
->comps_in_scan
> 1) {
73 coef
->MCU_rows_per_iMCU_row
= 1;
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
;
78 coef
->MCU_rows_per_iMCU_row
= cinfo
->cur_comp_info
[0]->last_row_height
;
82 coef
->MCU_vert_offset
= 0;