CentrED/Imaging/JpegLib/imjddctmgr.pas

329 lines
9.8 KiB
Plaintext

unit imjddctmgr;
{ Original : jddctmgr.c ; Copyright (C) 1994-1996, Thomas G. Lane. }
{ This file contains the inverse-DCT management logic.
This code selects a particular IDCT implementation to be used,
and it performs related housekeeping chores. No code in this file
is executed per IDCT step, only during output pass setup.
Note that the IDCT routines are responsible for performing coefficient
dequantization as well as the IDCT proper. This module sets up the
dequantization multiplier table needed by the IDCT routine. }
interface
{$I imjconfig.inc}
uses
imjmorecfg,
imjinclude,
imjdeferr,
imjerror,
imjpeglib,
imjdct, { Private declarations for DCT subsystem }
imjidctfst,
{$IFDEF BASM}
imjidctasm,
{$ELSE}
imjidctint,
{$ENDIF}
imjidctflt,
imjidctred;
{ Initialize IDCT manager. }
{GLOBAL}
procedure jinit_inverse_dct (cinfo : j_decompress_ptr);
implementation
{ The decompressor input side (jdinput.c) saves away the appropriate
quantization table for each component at the start of the first scan
involving that component. (This is necessary in order to correctly
decode files that reuse Q-table slots.)
When we are ready to make an output pass, the saved Q-table is converted
to a multiplier table that will actually be used by the IDCT routine.
The multiplier table contents are IDCT-method-dependent. To support
application changes in IDCT method between scans, we can remake the
multiplier tables if necessary.
In buffered-image mode, the first output pass may occur before any data
has been seen for some components, and thus before their Q-tables have
been saved away. To handle this case, multiplier tables are preset
to zeroes; the result of the IDCT will be a neutral gray level. }
{ Private subobject for this module }
type
my_idct_ptr = ^my_idct_controller;
my_idct_controller = record
pub : jpeg_inverse_dct; { public fields }
{ This array contains the IDCT method code that each multiplier table
is currently set up for, or -1 if it's not yet set up.
The actual multiplier tables are pointed to by dct_table in the
per-component comp_info structures. }
cur_method : array[0..MAX_COMPONENTS-1] of int;
end; {my_idct_controller;}
{ Allocated multiplier tables: big enough for any supported variant }
type
multiplier_table = record
case byte of
0:(islow_array : array[0..DCTSIZE2-1] of ISLOW_MULT_TYPE);
{$ifdef DCT_IFAST_SUPPORTED}
1:(ifast_array : array[0..DCTSIZE2-1] of IFAST_MULT_TYPE);
{$endif}
{$ifdef DCT_FLOAT_SUPPORTED}
2:(float_array : array[0..DCTSIZE2-1] of FLOAT_MULT_TYPE);
{$endif}
end;
{ The current scaled-IDCT routines require ISLOW-style multiplier tables,
so be sure to compile that code if either ISLOW or SCALING is requested. }
{$ifdef DCT_ISLOW_SUPPORTED}
{$define PROVIDE_ISLOW_TABLES}
{$else}
{$ifdef IDCT_SCALING_SUPPORTED}
{$define PROVIDE_ISLOW_TABLES}
{$endif}
{$endif}
{ Prepare for an output pass.
Here we select the proper IDCT routine for each component and build
a matching multiplier table. }
{METHODDEF}
procedure start_pass (cinfo : j_decompress_ptr);
var
idct : my_idct_ptr;
ci, i : int;
compptr : jpeg_component_info_ptr;
method : J_DCT_METHOD;
method_ptr : inverse_DCT_method_ptr;
qtbl : JQUANT_TBL_PTR;
{$ifdef PROVIDE_ISLOW_TABLES}
var
ismtbl : ISLOW_MULT_TYPE_FIELD_PTR;
{$endif}
{$ifdef DCT_IFAST_SUPPORTED}
const
CONST_BITS = 14;
const
aanscales : array[0..DCTSIZE2-1] of INT16 =
({ precomputed values scaled up by 14 bits }
16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247);
var
ifmtbl : IFAST_MULT_TYPE_FIELD_PTR;
{SHIFT_TEMPS}
{ Descale and correctly round an INT32 value that's scaled by N bits.
We assume RIGHT_SHIFT rounds towards minus infinity, so adding
the fudge factor is correct for either sign of X. }
function DESCALE(x : INT32; n : int) : INT32;
var
shift_temp : INT32;
begin
{$ifdef RIGHT_SHIFT_IS_UNSIGNED}
shift_temp := x + (INT32(1) shl (n-1));
if shift_temp < 0 then
Descale := (shift_temp shr n) or ((not INT32(0)) shl (32-n))
else
Descale := (shift_temp shr n);
{$else}
Descale := (x + (INT32(1) shl (n-1)) shr n;
{$endif}
end;
{$endif}
{$ifdef DCT_FLOAT_SUPPORTED}
const
aanscalefactor : array[0..DCTSIZE-1] of double =
(1.0, 1.387039845, 1.306562965, 1.175875602,
1.0, 0.785694958, 0.541196100, 0.275899379);
var
fmtbl : FLOAT_MULT_TYPE_FIELD_PTR;
row, col : int;
{$endif}
begin
idct := my_idct_ptr (cinfo^.idct);
method := J_DCT_METHOD(0);
method_ptr := NIL;
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
{ Select the proper IDCT routine for this component's scaling }
case (compptr^.DCT_scaled_size) of
{$ifdef IDCT_SCALING_SUPPORTED}
1:begin
method_ptr := jpeg_idct_1x1;
method := JDCT_ISLOW; { jidctred uses islow-style table }
end;
2:begin
method_ptr := jpeg_idct_2x2;
method := JDCT_ISLOW; { jidctred uses islow-style table }
end;
4:begin
method_ptr := jpeg_idct_4x4;
method := JDCT_ISLOW; { jidctred uses islow-style table }
end;
{$endif}
DCTSIZE:
case (cinfo^.dct_method) of
{$ifdef DCT_ISLOW_SUPPORTED}
JDCT_ISLOW:
begin
method_ptr := @jpeg_idct_islow;
method := JDCT_ISLOW;
end;
{$endif}
{$ifdef DCT_IFAST_SUPPORTED}
JDCT_IFAST:
begin
method_ptr := @jpeg_idct_ifast;
method := JDCT_IFAST;
end;
{$endif}
{$ifdef DCT_FLOAT_SUPPORTED}
JDCT_FLOAT:
begin
method_ptr := @jpeg_idct_float;
method := JDCT_FLOAT;
end;
{$endif}
else
ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
end;
else
ERREXIT1(j_common_ptr(cinfo), JERR_BAD_DCTSIZE, compptr^.DCT_scaled_size);
end;
idct^.pub.inverse_DCT[ci] := method_ptr;
{ Create multiplier table from quant table.
However, we can skip this if the component is uninteresting
or if we already built the table. Also, if no quant table
has yet been saved for the component, we leave the
multiplier table all-zero; we'll be reading zeroes from the
coefficient controller's buffer anyway. }
if (not compptr^.component_needed) or (idct^.cur_method[ci] = int(method)) then
continue;
qtbl := compptr^.quant_table;
if (qtbl = NIL) then { happens if no data yet for component }
continue;
idct^.cur_method[ci] := int(method);
case (method) of
{$ifdef PROVIDE_ISLOW_TABLES}
JDCT_ISLOW:
begin
{ For LL&M IDCT method, multipliers are equal to raw quantization
coefficients, but are stored as ints to ensure access efficiency. }
ismtbl := ISLOW_MULT_TYPE_FIELD_PTR (compptr^.dct_table);
for i := 0 to pred(DCTSIZE2) do
begin
ismtbl^[i] := ISLOW_MULT_TYPE (qtbl^.quantval[i]);
end;
end;
{$endif}
{$ifdef DCT_IFAST_SUPPORTED}
JDCT_IFAST:
begin
{ For AA&N IDCT method, multipliers are equal to quantization
coefficients scaled by scalefactor[row]*scalefactor[col], where
scalefactor[0] := 1
scalefactor[k] := cos(k*PI/16) * sqrt(2) for k=1..7
For integer operation, the multiplier table is to be scaled by
IFAST_SCALE_BITS. }
ifmtbl := IFAST_MULT_TYPE_FIELD_PTR (compptr^.dct_table);
for i := 0 to pred(DCTSIZE2) do
begin
ifmtbl^[i] := IFAST_MULT_TYPE(
DESCALE( INT32 (qtbl^.quantval[i]) * INT32 (aanscales[i]),
CONST_BITS-IFAST_SCALE_BITS) );
end;
end;
{$endif}
{$ifdef DCT_FLOAT_SUPPORTED}
JDCT_FLOAT:
begin
{ For float AA&N IDCT method, multipliers are equal to quantization
coefficients scaled by scalefactor[row]*scalefactor[col], where
scalefactor[0] := 1
scalefactor[k] := cos(k*PI/16) * sqrt(2) for k=1..7 }
fmtbl := FLOAT_MULT_TYPE_FIELD_PTR(compptr^.dct_table);
i := 0;
for row := 0 to pred(DCTSIZE) do
begin
for col := 0 to pred(DCTSIZE) do
begin
fmtbl^[i] := {FLOAT_MULT_TYPE} (
{double} qtbl^.quantval[i] *
aanscalefactor[row] * aanscalefactor[col] );
Inc(i);
end;
end;
end;
{$endif}
else
ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
break;
end;
Inc(compptr);
end;
end;
{ Initialize IDCT manager. }
{GLOBAL}
procedure jinit_inverse_dct (cinfo : j_decompress_ptr);
var
idct : my_idct_ptr;
ci : int;
compptr : jpeg_component_info_ptr;
begin
idct := my_idct_ptr(
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
SIZEOF(my_idct_controller)) );
cinfo^.idct := jpeg_inverse_dct_ptr (idct);
idct^.pub.start_pass := start_pass;
compptr := jpeg_component_info_ptr(cinfo^.comp_info);
for ci := 0 to pred(cinfo^.num_components) do
begin
{ Allocate and pre-zero a multiplier table for each component }
compptr^.dct_table :=
cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
SIZEOF(multiplier_table));
MEMZERO(compptr^.dct_table, SIZEOF(multiplier_table));
{ Mark multiplier table not yet set up for any method }
idct^.cur_method[ci] := -1;
Inc(compptr);
end;
end;
end.