CentrED/Imaging/JpegLib/imjcprepct.pas

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2022-05-08 10:47:53 +02:00
unit imjcprepct;
{ Original : jcprepct.c ; Copyright (C) 1994-1996, Thomas G. Lane. }
{ This file contains the compression preprocessing controller.
This controller manages the color conversion, downsampling,
and edge expansion steps.
Most of the complexity here is associated with buffering input rows
as required by the downsampler. See the comments at the head of
jcsample.c for the downsampler's needs. }
interface
{$I imjconfig.inc}
uses
imjmorecfg,
imjpeglib,
imjdeferr,
imjerror,
imjinclude,
imjutils;
{GLOBAL}
procedure jinit_c_prep_controller (cinfo : j_compress_ptr;
need_full_buffer : boolean);
implementation
{ At present, jcsample.c can request context rows only for smoothing.
In the future, we might also need context rows for CCIR601 sampling
or other more-complex downsampling procedures. The code to support
context rows should be compiled only if needed. }
{$ifdef INPUT_SMOOTHING_SUPPORTED}
{$define CONTEXT_ROWS_SUPPORTED}
{$endif}
{ For the simple (no-context-row) case, we just need to buffer one
row group's worth of pixels for the downsampling step. At the bottom of
the image, we pad to a full row group by replicating the last pixel row.
The downsampler's last output row is then replicated if needed to pad
out to a full iMCU row.
When providing context rows, we must buffer three row groups' worth of
pixels. Three row groups are physically allocated, but the row pointer
arrays are made five row groups high, with the extra pointers above and
below "wrapping around" to point to the last and first real row groups.
This allows the downsampler to access the proper context rows.
At the top and bottom of the image, we create dummy context rows by
copying the first or last real pixel row. This copying could be avoided
by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
trouble on the compression side. }
{ Private buffer controller object }
type
my_prep_ptr = ^my_prep_controller;
my_prep_controller = record
pub : jpeg_c_prep_controller; { public fields }
{ Downsampling input buffer. This buffer holds color-converted data
until we have enough to do a downsample step. }
color_buf : array[0..MAX_COMPONENTS-1] of JSAMPARRAY;
rows_to_go : JDIMENSION; { counts rows remaining in source image }
next_buf_row : int; { index of next row to store in color_buf }
{$ifdef CONTEXT_ROWS_SUPPORTED} { only needed for context case }
this_row_group : int; { starting row index of group to process }
next_buf_stop : int; { downsample when we reach this index }
{$endif}
end; {my_prep_controller;}
{ Initialize for a processing pass. }
{METHODDEF}
procedure start_pass_prep (cinfo : j_compress_ptr;
pass_mode : J_BUF_MODE );
var
prep : my_prep_ptr;
begin
prep := my_prep_ptr (cinfo^.prep);
if (pass_mode <> JBUF_PASS_THRU) then
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
{ Initialize total-height counter for detecting bottom of image }
prep^.rows_to_go := cinfo^.image_height;
{ Mark the conversion buffer empty }
prep^.next_buf_row := 0;
{$ifdef CONTEXT_ROWS_SUPPORTED}
{ Preset additional state variables for context mode.
These aren't used in non-context mode, so we needn't test which mode. }
prep^.this_row_group := 0;
{ Set next_buf_stop to stop after two row groups have been read in. }
prep^.next_buf_stop := 2 * cinfo^.max_v_samp_factor;
{$endif}
end;
{ Expand an image vertically from height input_rows to height output_rows,
by duplicating the bottom row. }
{LOCAL}
procedure expand_bottom_edge (image_data : JSAMPARRAY;
num_cols : JDIMENSION;
input_rows : int;
output_rows : int);
var
{register} row : int;
begin
for row := input_rows to pred(output_rows) do
begin
jcopy_sample_rows(image_data, input_rows-1, image_data, row,
1, num_cols);
end;
end;
{ Process some data in the simple no-context case.
Preprocessor output data is counted in "row groups". A row group
is defined to be v_samp_factor sample rows of each component.
Downsampling will produce this much data from each max_v_samp_factor
input rows. }
{METHODDEF}
procedure pre_process_data (cinfo : j_compress_ptr;
input_buf : JSAMPARRAY;
var in_row_ctr : JDIMENSION;
in_rows_avail : JDIMENSION;
output_buf : JSAMPIMAGE;
var out_row_group_ctr : JDIMENSION;
out_row_groups_avail : JDIMENSION);
var
prep : my_prep_ptr;
numrows, ci : int;
inrows : JDIMENSION;
compptr : jpeg_component_info_ptr;
var
local_input_buf : JSAMPARRAY;
begin
prep := my_prep_ptr (cinfo^.prep);
while (in_row_ctr < in_rows_avail) and
(out_row_group_ctr < out_row_groups_avail) do
begin
{ Do color conversion to fill the conversion buffer. }
inrows := in_rows_avail - in_row_ctr;
numrows := cinfo^.max_v_samp_factor - prep^.next_buf_row;
{numrows := int( MIN(JDIMENSION(numrows), inrows) );}
if inrows < JDIMENSION(numrows) then
numrows := int(inrows);
local_input_buf := JSAMPARRAY(@(input_buf^[in_row_ctr]));
cinfo^.cconvert^.color_convert (cinfo, local_input_buf,
JSAMPIMAGE(@prep^.color_buf),
JDIMENSION(prep^.next_buf_row),
numrows);
Inc(in_row_ctr, numrows);
Inc(prep^.next_buf_row, numrows);
Dec(prep^.rows_to_go, numrows);
{ If at bottom of image, pad to fill the conversion buffer. }
if (prep^.rows_to_go = 0) and
(prep^.next_buf_row < cinfo^.max_v_samp_factor) then
begin
for ci := 0 to pred(cinfo^.num_components) do
begin
expand_bottom_edge(prep^.color_buf[ci], cinfo^.image_width,
prep^.next_buf_row, cinfo^.max_v_samp_factor);
end;
prep^.next_buf_row := cinfo^.max_v_samp_factor;
end;
{ If we've filled the conversion buffer, empty it. }
if (prep^.next_buf_row = cinfo^.max_v_samp_factor) then
begin
cinfo^.downsample^.downsample (cinfo,
JSAMPIMAGE(@prep^.color_buf),
JDIMENSION (0),
output_buf,
out_row_group_ctr);
prep^.next_buf_row := 0;
Inc(out_row_group_ctr);;
end;
{ If at bottom of image, pad the output to a full iMCU height.
Note we assume the caller is providing a one-iMCU-height output buffer! }
if (prep^.rows_to_go = 0) and
(out_row_group_ctr < out_row_groups_avail) then
begin
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
expand_bottom_edge(output_buf^[ci],
compptr^.width_in_blocks * DCTSIZE,
int (out_row_group_ctr) * compptr^.v_samp_factor,
int (out_row_groups_avail) * compptr^.v_samp_factor);
Inc(compptr);
end;
out_row_group_ctr := out_row_groups_avail;
break; { can exit outer loop without test }
end;
end;
end;
{$ifdef CONTEXT_ROWS_SUPPORTED}
{ Process some data in the context case. }
{METHODDEF}
procedure pre_process_context (cinfo : j_compress_ptr;
input_buf : JSAMPARRAY;
var in_row_ctr : JDIMENSION;
in_rows_avail : JDIMENSION;
output_buf : JSAMPIMAGE;
var out_row_group_ctr : JDIMENSION;
out_row_groups_avail : JDIMENSION);
var
prep : my_prep_ptr;
numrows, ci : int;
buf_height : int;
inrows : JDIMENSION;
var
row : int;
begin
prep := my_prep_ptr (cinfo^.prep);
buf_height := cinfo^.max_v_samp_factor * 3;
while (out_row_group_ctr < out_row_groups_avail) do
begin
if (in_row_ctr < in_rows_avail) then
begin
{ Do color conversion to fill the conversion buffer. }
inrows := in_rows_avail - in_row_ctr;
numrows := prep^.next_buf_stop - prep^.next_buf_row;
{numrows := int ( MIN( JDIMENSION(numrows), inrows) );}
if inrows < JDIMENSION(numrows) then
numrows := int(inrows);
cinfo^.cconvert^.color_convert (cinfo,
JSAMPARRAY(@input_buf^[in_row_ctr]),
JSAMPIMAGE(@prep^.color_buf),
JDIMENSION (prep^.next_buf_row),
numrows);
{ Pad at top of image, if first time through }
if (prep^.rows_to_go = cinfo^.image_height) then
begin
for ci := 0 to pred(cinfo^.num_components) do
begin
for row := 1 to cinfo^.max_v_samp_factor do
begin
jcopy_sample_rows(prep^.color_buf[ci], 0,
prep^.color_buf[ci], -row,
1, cinfo^.image_width);
end;
end;
end;
Inc(in_row_ctr, numrows);
Inc(prep^.next_buf_row, numrows);
Dec(prep^.rows_to_go, numrows);
end
else
begin
{ Return for more data, unless we are at the bottom of the image. }
if (prep^.rows_to_go <> 0) then
break;
{ When at bottom of image, pad to fill the conversion buffer. }
if (prep^.next_buf_row < prep^.next_buf_stop) then
begin
for ci := 0 to pred(cinfo^.num_components) do
begin
expand_bottom_edge(prep^.color_buf[ci], cinfo^.image_width,
prep^.next_buf_row, prep^.next_buf_stop);
end;
prep^.next_buf_row := prep^.next_buf_stop;
end;
end;
{ If we've gotten enough data, downsample a row group. }
if (prep^.next_buf_row = prep^.next_buf_stop) then
begin
cinfo^.downsample^.downsample (cinfo,
JSAMPIMAGE(@prep^.color_buf),
JDIMENSION(prep^.this_row_group),
output_buf,
out_row_group_ctr);
Inc(out_row_group_ctr);
{ Advance pointers with wraparound as necessary. }
Inc(prep^.this_row_group, cinfo^.max_v_samp_factor);
if (prep^.this_row_group >= buf_height) then
prep^.this_row_group := 0;
if (prep^.next_buf_row >= buf_height) then
prep^.next_buf_row := 0;
prep^.next_buf_stop := prep^.next_buf_row + cinfo^.max_v_samp_factor;
end;
end;
end;
{ Create the wrapped-around downsampling input buffer needed for context mode. }
{LOCAL}
procedure create_context_buffer (cinfo : j_compress_ptr);
var
prep : my_prep_ptr;
rgroup_height : int;
ci, i : int;
compptr : jpeg_component_info_ptr;
true_buffer, fake_buffer : JSAMPARRAY;
begin
prep := my_prep_ptr (cinfo^.prep);
rgroup_height := cinfo^.max_v_samp_factor;
{ Grab enough space for fake row pointers for all the components;
we need five row groups' worth of pointers for each component. }
fake_buffer := JSAMPARRAY(
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
(cinfo^.num_components * 5 * rgroup_height) *
SIZEOF(JSAMPROW)) );
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
{ Allocate the actual buffer space (3 row groups) for this component.
We make the buffer wide enough to allow the downsampler to edge-expand
horizontally within the buffer, if it so chooses. }
true_buffer := cinfo^.mem^.alloc_sarray
(j_common_ptr(cinfo), JPOOL_IMAGE,
JDIMENSION (( long(compptr^.width_in_blocks) * DCTSIZE *
cinfo^.max_h_samp_factor) div compptr^.h_samp_factor),
JDIMENSION (3 * rgroup_height));
{ Copy true buffer row pointers into the middle of the fake row array }
MEMCOPY(JSAMPARRAY(@ fake_buffer^[rgroup_height]), true_buffer,
3 * rgroup_height * SIZEOF(JSAMPROW));
{ Fill in the above and below wraparound pointers }
for i := 0 to pred(rgroup_height) do
begin
fake_buffer^[i] := true_buffer^[2 * rgroup_height + i];
fake_buffer^[4 * rgroup_height + i] := true_buffer^[i];
end;
prep^.color_buf[ci] := JSAMPARRAY(@ fake_buffer^[rgroup_height]);
Inc(JSAMPROW_PTR(fake_buffer), 5 * rgroup_height); { point to space for next component }
Inc(compptr);
end;
end;
{$endif} { CONTEXT_ROWS_SUPPORTED }
{ Initialize preprocessing controller. }
{GLOBAL}
procedure jinit_c_prep_controller (cinfo : j_compress_ptr;
need_full_buffer : boolean);
var
prep : my_prep_ptr;
ci : int;
compptr : jpeg_component_info_ptr;
begin
if (need_full_buffer) then { safety check }
ERREXIT(j_common_ptr(cinfo), JERR_BAD_BUFFER_MODE);
prep := my_prep_ptr(
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
SIZEOF(my_prep_controller)) );
cinfo^.prep := jpeg_c_prep_controller_ptr(prep);
prep^.pub.start_pass := start_pass_prep;
{ Allocate the color conversion buffer.
We make the buffer wide enough to allow the downsampler to edge-expand
horizontally within the buffer, if it so chooses. }
if (cinfo^.downsample^.need_context_rows) then
begin
{ Set up to provide context rows }
{$ifdef CONTEXT_ROWS_SUPPORTED}
prep^.pub.pre_process_data := pre_process_context;
create_context_buffer(cinfo);
{$else}
ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
{$endif}
end
else
begin
{ No context, just make it tall enough for one row group }
prep^.pub.pre_process_data := pre_process_data;
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
prep^.color_buf[ci] := cinfo^.mem^.alloc_sarray
(j_common_ptr(cinfo), JPOOL_IMAGE,
JDIMENSION (( long(compptr^.width_in_blocks) * DCTSIZE *
cinfo^.max_h_samp_factor) div compptr^.h_samp_factor),
JDIMENSION(cinfo^.max_v_samp_factor) );
Inc(compptr);
end;
end;
end;
end.