CentrED/Imaging/JpegLib/imjccoefct.pas

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unit imjccoefct;
{ This file contains the coefficient buffer controller for compression.
This controller is the top level of the JPEG compressor proper.
The coefficient buffer lies between forward-DCT and entropy encoding steps.}
{ Original: jccoefct.c; Copyright (C) 1994-1997, Thomas G. Lane. }
interface
{$I imjconfig.inc}
uses
imjmorecfg,
imjinclude,
imjerror,
imjdeferr,
imjutils,
imjpeglib;
{ We use a full-image coefficient buffer when doing Huffman optimization,
and also for writing multiple-scan JPEG files. In all cases, the DCT
step is run during the first pass, and subsequent passes need only read
the buffered coefficients. }
{$ifdef ENTROPY_OPT_SUPPORTED}
{$define FULL_COEF_BUFFER_SUPPORTED}
{$else}
{$ifdef C_MULTISCAN_FILES_SUPPORTED}
{$define FULL_COEF_BUFFER_SUPPORTED}
{$endif}
{$endif}
{ Initialize coefficient buffer controller. }
{GLOBAL}
procedure jinit_c_coef_controller (cinfo : j_compress_ptr;
need_full_buffer : boolean);
implementation
{ Private buffer controller object }
type
my_coef_ptr = ^my_coef_controller;
my_coef_controller = record
pub : jpeg_c_coef_controller; { public fields }
iMCU_row_num : JDIMENSION; { iMCU row # within image }
mcu_ctr : JDIMENSION; { counts MCUs processed in current row }
MCU_vert_offset : int; { counts MCU rows within iMCU row }
MCU_rows_per_iMCU_row : int; { number of such rows needed }
{ For single-pass compression, it's sufficient to buffer just one MCU
(although this may prove a bit slow in practice). We allocate a
workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
MCU constructed and sent. (On 80x86, the workspace is FAR even though
it's not really very big; this is to keep the module interfaces unchanged
when a large coefficient buffer is necessary.)
In multi-pass modes, this array points to the current MCU's blocks
within the virtual arrays. }
MCU_buffer : array[0..C_MAX_BLOCKS_IN_MCU-1] of JBLOCKROW;
{ In multi-pass modes, we need a virtual block array for each component. }
whole_image : array[0..MAX_COMPONENTS-1] of jvirt_barray_ptr;
end;
{ Forward declarations }
{METHODDEF}
function compress_data(cinfo : j_compress_ptr;
input_buf : JSAMPIMAGE) : boolean; forward;
{$ifdef FULL_COEF_BUFFER_SUPPORTED}
{METHODDEF}
function compress_first_pass(cinfo : j_compress_ptr;
input_buf : JSAMPIMAGE) : boolean; forward;
{METHODDEF}
function compress_output(cinfo : j_compress_ptr;
input_buf : JSAMPIMAGE) : boolean; forward;
{$endif}
{LOCAL}
procedure start_iMCU_row (cinfo : j_compress_ptr);
{ Reset within-iMCU-row counters for a new row }
var
coef : my_coef_ptr;
begin
coef := my_coef_ptr (cinfo^.coef);
{ In an interleaved scan, an MCU row is the same as an iMCU row.
In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
But at the bottom of the image, process only what's left. }
if (cinfo^.comps_in_scan > 1) then
begin
coef^.MCU_rows_per_iMCU_row := 1;
end
else
begin
if (coef^.iMCU_row_num < (cinfo^.total_iMCU_rows-1)) then
coef^.MCU_rows_per_iMCU_row := cinfo^.cur_comp_info[0]^.v_samp_factor
else
coef^.MCU_rows_per_iMCU_row := cinfo^.cur_comp_info[0]^.last_row_height;
end;
coef^.mcu_ctr := 0;
coef^.MCU_vert_offset := 0;
end;
{ Initialize for a processing pass. }
{METHODDEF}
procedure start_pass_coef (cinfo : j_compress_ptr;
pass_mode : J_BUF_MODE);
var
coef : my_coef_ptr;
begin
coef := my_coef_ptr (cinfo^.coef);
coef^.iMCU_row_num := 0;
start_iMCU_row(cinfo);
case (pass_mode) of
JBUF_PASS_THRU:
begin
if (coef^.whole_image[0] <> NIL) then
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
coef^.pub.compress_data := compress_data;
end;
{$ifdef FULL_COEF_BUFFER_SUPPORTED}
JBUF_SAVE_AND_PASS:
begin
if (coef^.whole_image[0] = NIL) then
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
coef^.pub.compress_data := compress_first_pass;
end;
JBUF_CRANK_DEST:
begin
if (coef^.whole_image[0] = NIL) then
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
coef^.pub.compress_data := compress_output;
end;
{$endif}
else
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
end;
end;
{ Process some data in the single-pass case.
We process the equivalent of one fully interleaved MCU row ("iMCU" row)
per call, ie, v_samp_factor block rows for each component in the image.
Returns TRUE if the iMCU row is completed, FALSE if suspended.
NB: input_buf contains a plane for each component in image,
which we index according to the component's SOF position. }
{METHODDEF}
function compress_data (cinfo : j_compress_ptr;
input_buf : JSAMPIMAGE) : boolean;
var
coef : my_coef_ptr;
MCU_col_num : JDIMENSION; { index of current MCU within row }
last_MCU_col : JDIMENSION;
last_iMCU_row : JDIMENSION;
blkn, bi, ci, yindex, yoffset, blockcnt : int;
ypos, xpos : JDIMENSION;
compptr : jpeg_component_info_ptr;
begin
coef := my_coef_ptr (cinfo^.coef);
last_MCU_col := cinfo^.MCUs_per_row - 1;
last_iMCU_row := cinfo^.total_iMCU_rows - 1;
{ Loop to write as much as one whole iMCU row }
for yoffset := coef^.MCU_vert_offset to pred(coef^.MCU_rows_per_iMCU_row) do
begin
for MCU_col_num := coef^.mcu_ctr to last_MCU_col do
begin
{ Determine where data comes from in input_buf and do the DCT thing.
Each call on forward_DCT processes a horizontal row of DCT blocks
as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
sequentially. Dummy blocks at the right or bottom edge are filled in
specially. The data in them does not matter for image reconstruction,
so we fill them with values that will encode to the smallest amount of
data, viz: all zeroes in the AC entries, DC entries equal to previous
block's DC value. (Thanks to Thomas Kinsman for this idea.) }
blkn := 0;
for ci := 0 to pred(cinfo^.comps_in_scan) do
begin
compptr := cinfo^.cur_comp_info[ci];
if (MCU_col_num < last_MCU_col) then
blockcnt := compptr^.MCU_width
else
blockcnt := compptr^.last_col_width;
xpos := MCU_col_num * JDIMENSION(compptr^.MCU_sample_width);
ypos := yoffset * DCTSIZE; { ypos = (yoffset+yindex) * DCTSIZE }
for yindex := 0 to pred(compptr^.MCU_height) do
begin
if (coef^.iMCU_row_num < last_iMCU_row) or
(yoffset+yindex < compptr^.last_row_height) then
begin
cinfo^.fdct^.forward_DCT (cinfo, compptr,
input_buf^[compptr^.component_index],
coef^.MCU_buffer[blkn],
ypos, xpos, JDIMENSION (blockcnt));
if (blockcnt < compptr^.MCU_width) then
begin
{ Create some dummy blocks at the right edge of the image. }
jzero_far({FAR}pointer(coef^.MCU_buffer[blkn + blockcnt]),
(compptr^.MCU_width - blockcnt) * SIZEOF(JBLOCK));
for bi := blockcnt to pred(compptr^.MCU_width) do
begin
coef^.MCU_buffer[blkn+bi]^[0][0] := coef^.MCU_buffer[blkn+bi-1]^[0][0];
end;
end;
end
else
begin
{ Create a row of dummy blocks at the bottom of the image. }
jzero_far({FAR}pointer(coef^.MCU_buffer[blkn]),
compptr^.MCU_width * SIZEOF(JBLOCK));
for bi := 0 to pred(compptr^.MCU_width) do
begin
coef^.MCU_buffer[blkn+bi]^[0][0] := coef^.MCU_buffer[blkn-1]^[0][0];
end;
end;
Inc(blkn, compptr^.MCU_width);
Inc(ypos, DCTSIZE);
end;
end;
{ Try to write the MCU. In event of a suspension failure, we will
re-DCT the MCU on restart (a bit inefficient, could be fixed...) }
if (not cinfo^.entropy^.encode_mcu (cinfo, JBLOCKARRAY(@coef^.MCU_buffer)^)) then
begin
{ Suspension forced; update state counters and exit }
coef^.MCU_vert_offset := yoffset;
coef^.mcu_ctr := MCU_col_num;
compress_data := FALSE;
exit;
end;
end;
{ Completed an MCU row, but perhaps not an iMCU row }
coef^.mcu_ctr := 0;
end;
{ Completed the iMCU row, advance counters for next one }
Inc(coef^.iMCU_row_num);
start_iMCU_row(cinfo);
compress_data := TRUE;
end;
{$ifdef FULL_COEF_BUFFER_SUPPORTED}
{ Process some data in the first pass of a multi-pass case.
We process the equivalent of one fully interleaved MCU row ("iMCU" row)
per call, ie, v_samp_factor block rows for each component in the image.
This amount of data is read from the source buffer, DCT'd and quantized,
and saved into the virtual arrays. We also generate suitable dummy blocks
as needed at the right and lower edges. (The dummy blocks are constructed
in the virtual arrays, which have been padded appropriately.) This makes
it possible for subsequent passes not to worry about real vs. dummy blocks.
We must also emit the data to the entropy encoder. This is conveniently
done by calling compress_output() after we've loaded the current strip
of the virtual arrays.
NB: input_buf contains a plane for each component in image. All
components are DCT'd and loaded into the virtual arrays in this pass.
However, it may be that only a subset of the components are emitted to
the entropy encoder during this first pass; be careful about looking
at the scan-dependent variables (MCU dimensions, etc). }
{METHODDEF}
function compress_first_pass (cinfo : j_compress_ptr;
input_buf : JSAMPIMAGE) : boolean;
var
coef : my_coef_ptr;
last_iMCU_row : JDIMENSION;
blocks_across, MCUs_across, MCUindex : JDIMENSION;
bi, ci, h_samp_factor, block_row, block_rows, ndummy : int;
lastDC : JCOEF;
compptr : jpeg_component_info_ptr;
buffer : JBLOCKARRAY;
thisblockrow, lastblockrow : JBLOCKROW;
begin
coef := my_coef_ptr (cinfo^.coef);
last_iMCU_row := cinfo^.total_iMCU_rows - 1;
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
{ Align the virtual buffer for this component. }
buffer := cinfo^.mem^.access_virt_barray
(j_common_ptr(cinfo), coef^.whole_image[ci],
coef^.iMCU_row_num * JDIMENSION(compptr^.v_samp_factor),
JDIMENSION (compptr^.v_samp_factor), TRUE);
{ Count non-dummy DCT block rows in this iMCU row. }
if (coef^.iMCU_row_num < last_iMCU_row) then
block_rows := compptr^.v_samp_factor
else
begin
{ NB: can't use last_row_height here, since may not be set! }
block_rows := int (compptr^.height_in_blocks) mod compptr^.v_samp_factor;
if (block_rows = 0) then
block_rows := compptr^.v_samp_factor;
end;
blocks_across := compptr^.width_in_blocks;
h_samp_factor := compptr^.h_samp_factor;
{ Count number of dummy blocks to be added at the right margin. }
ndummy := int (blocks_across) mod h_samp_factor;
if (ndummy > 0) then
ndummy := h_samp_factor - ndummy;
{ Perform DCT for all non-dummy blocks in this iMCU row. Each call
on forward_DCT processes a complete horizontal row of DCT blocks. }
for block_row := 0 to pred(block_rows) do
begin
thisblockrow := buffer^[block_row];
cinfo^.fdct^.forward_DCT (cinfo, compptr,
input_buf^[ci],
thisblockrow,
JDIMENSION (block_row * DCTSIZE),
JDIMENSION (0),
blocks_across);
if (ndummy > 0) then
begin
{ Create dummy blocks at the right edge of the image. }
Inc(JBLOCK_PTR(thisblockrow), blocks_across); { => first dummy block }
jzero_far({FAR}pointer(thisblockrow), ndummy * SIZEOF(JBLOCK));
{lastDC := thisblockrow^[-1][0];}
{ work around Range Checking }
Dec(JBLOCK_PTR(thisblockrow));
lastDC := thisblockrow^[0][0];
Inc(JBLOCK_PTR(thisblockrow));
for bi := 0 to pred(ndummy) do
begin
thisblockrow^[bi][0] := lastDC;
end;
end;
end;
{ If at end of image, create dummy block rows as needed.
The tricky part here is that within each MCU, we want the DC values
of the dummy blocks to match the last real block's DC value.
This squeezes a few more bytes out of the resulting file... }
if (coef^.iMCU_row_num = last_iMCU_row) then
begin
Inc(blocks_across, ndummy); { include lower right corner }
MCUs_across := blocks_across div JDIMENSION(h_samp_factor);
for block_row := block_rows to pred(compptr^.v_samp_factor) do
begin
thisblockrow := buffer^[block_row];
lastblockrow := buffer^[block_row-1];
jzero_far({FAR} pointer(thisblockrow),
size_t(blocks_across * SIZEOF(JBLOCK)));
for MCUindex := 0 to pred(MCUs_across) do
begin
lastDC := lastblockrow^[h_samp_factor-1][0];
for bi := 0 to pred(h_samp_factor) do
begin
thisblockrow^[bi][0] := lastDC;
end;
Inc(JBLOCK_PTR(thisblockrow), h_samp_factor); { advance to next MCU in row }
Inc(JBLOCK_PTR(lastblockrow), h_samp_factor);
end;
end;
end;
Inc(compptr);
end;
{ NB: compress_output will increment iMCU_row_num if successful.
A suspension return will result in redoing all the work above next time.}
{ Emit data to the entropy encoder, sharing code with subsequent passes }
compress_first_pass := compress_output(cinfo, input_buf);
end;
{ Process some data in subsequent passes of a multi-pass case.
We process the equivalent of one fully interleaved MCU row ("iMCU" row)
per call, ie, v_samp_factor block rows for each component in the scan.
The data is obtained from the virtual arrays and fed to the entropy coder.
Returns TRUE if the iMCU row is completed, FALSE if suspended.
NB: input_buf is ignored; it is likely to be a NIL pointer. }
{METHODDEF}
function compress_output (cinfo : j_compress_ptr;
input_buf : JSAMPIMAGE) : boolean;
var
coef : my_coef_ptr;
MCU_col_num : JDIMENSION; { index of current MCU within row }
blkn, ci, xindex, yindex, yoffset : int;
start_col : JDIMENSION;
buffer : array[0..MAX_COMPS_IN_SCAN-1] of JBLOCKARRAY;
buffer_ptr : JBLOCKROW;
compptr : jpeg_component_info_ptr;
begin
coef := my_coef_ptr (cinfo^.coef);
{ Align the virtual buffers for the components used in this scan.
NB: during first pass, this is safe only because the buffers will
already be aligned properly, so jmemmgr.c won't need to do any I/O. }
for ci := 0 to pred(cinfo^.comps_in_scan) do
begin
compptr := cinfo^.cur_comp_info[ci];
buffer[ci] := cinfo^.mem^.access_virt_barray (
j_common_ptr(cinfo), coef^.whole_image[compptr^.component_index],
coef^.iMCU_row_num * JDIMENSION(compptr^.v_samp_factor),
JDIMENSION (compptr^.v_samp_factor), FALSE);
end;
{ Loop to process one whole iMCU row }
for yoffset := coef^.MCU_vert_offset to pred(coef^.MCU_rows_per_iMCU_row) do
begin
for MCU_col_num := coef^.mcu_ctr to pred(cinfo^.MCUs_per_row) do
begin
{ Construct list of pointers to DCT blocks belonging to this MCU }
blkn := 0; { index of current DCT block within MCU }
for ci := 0 to pred(cinfo^.comps_in_scan) do
begin
compptr := cinfo^.cur_comp_info[ci];
start_col := MCU_col_num * JDIMENSION(compptr^.MCU_width);
for yindex := 0 to pred(compptr^.MCU_height) do
begin
buffer_ptr := JBLOCKROW(@ buffer[ci]^[yindex+yoffset]^[start_col]);
for xindex := 0 to pred(compptr^.MCU_width) do
begin
coef^.MCU_buffer[blkn] := buffer_ptr;
Inc(blkn);
Inc(JBLOCK_PTR(buffer_ptr));
end;
end;
end;
{ Try to write the MCU. }
if (not cinfo^.entropy^.encode_mcu (cinfo, coef^.MCU_buffer)) then
begin
{ Suspension forced; update state counters and exit }
coef^.MCU_vert_offset := yoffset;
coef^.mcu_ctr := MCU_col_num;
compress_output := FALSE;
exit;
end;
end;
{ Completed an MCU row, but perhaps not an iMCU row }
coef^.mcu_ctr := 0;
end;
{ Completed the iMCU row, advance counters for next one }
Inc(coef^.iMCU_row_num);
start_iMCU_row(cinfo);
compress_output := TRUE;
end;
{$endif} { FULL_COEF_BUFFER_SUPPORTED }
{ Initialize coefficient buffer controller. }
{GLOBAL}
procedure jinit_c_coef_controller (cinfo : j_compress_ptr;
need_full_buffer : boolean);
var
coef : my_coef_ptr;
var
buffer : JBLOCKROW;
i : int;
var
ci : int;
compptr : jpeg_component_info_ptr;
begin
coef := my_coef_ptr (
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
SIZEOF(my_coef_controller)) );
cinfo^.coef := jpeg_c_coef_controller_ptr(coef);
coef^.pub.start_pass := start_pass_coef;
{ Create the coefficient buffer. }
if (need_full_buffer) then
begin
{$ifdef FULL_COEF_BUFFER_SUPPORTED}
{ Allocate a full-image virtual array for each component, }
{ padded to a multiple of samp_factor DCT blocks in each direction. }
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
coef^.whole_image[ci] := cinfo^.mem^.request_virt_barray
(j_common_ptr(cinfo), JPOOL_IMAGE, FALSE,
JDIMENSION (jround_up( long (compptr^.width_in_blocks),
long (compptr^.h_samp_factor) )),
JDIMENSION (jround_up(long (compptr^.height_in_blocks),
long (compptr^.v_samp_factor))),
JDIMENSION (compptr^.v_samp_factor));
Inc(compptr);
end;
{$else}
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
{$endif}
end
else
begin
{ We only need a single-MCU buffer. }
buffer := JBLOCKROW (
cinfo^.mem^.alloc_large (j_common_ptr(cinfo), JPOOL_IMAGE,
C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK)) );
for i := 0 to pred(C_MAX_BLOCKS_IN_MCU) do
begin
coef^.MCU_buffer[i] := JBLOCKROW(@ buffer^[i]);
end;
coef^.whole_image[0] := NIL; { flag for no virtual arrays }
end;
end;
end.