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CentrED/Imaging/JpegLib/imjidctred.pas

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unit imjidctred;
{ This file contains inverse-DCT routines that produce reduced-size output:
either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step
with an 8-to-4 step that produces the four averages of two adjacent outputs
(or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
These steps were derived by computing the corresponding values at the end
of the normal LL&M code, then simplifying as much as possible.
1x1 is trivial: just take the DC coefficient divided by 8.
See jidctint.c for additional comments. }
{ Original : jidctred.c ; Copyright (C) 1994-1998, Thomas G. Lane. }
interface
{$I imjconfig.inc}
uses
imjmorecfg,
imjinclude,
imjpeglib,
imjdct; { Private declarations for DCT subsystem }
{ Perform dequantization and inverse DCT on one block of coefficients,
producing a reduced-size 1x1 output block. }
{GLOBAL}
procedure jpeg_idct_1x1 (cinfo : j_decompress_ptr;
compptr : jpeg_component_info_ptr;
coef_block : JCOEFPTR;
output_buf : JSAMPARRAY;
output_col : JDIMENSION);
{ Perform dequantization and inverse DCT on one block of coefficients,
producing a reduced-size 2x2 output block. }
{GLOBAL}
procedure jpeg_idct_2x2 (cinfo : j_decompress_ptr;
compptr : jpeg_component_info_ptr;
coef_block : JCOEFPTR;
output_buf : JSAMPARRAY;
output_col : JDIMENSION);
{ Perform dequantization and inverse DCT on one block of coefficients,
producing a reduced-size 4x4 output block. }
{GLOBAL}
procedure jpeg_idct_4x4 (cinfo : j_decompress_ptr;
compptr : jpeg_component_info_ptr;
coef_block : JCOEFPTR;
output_buf : JSAMPARRAY;
output_col : JDIMENSION);
implementation
{ This module is specialized to the case DCTSIZE = 8. }
{$ifndef DCTSIZE_IS_8}
Sorry, this code only copes with 8x8 DCTs. { deliberate syntax err }
{$endif}
{ Scaling is the same as in jidctint.c. }
{$ifdef BITS_IN_JSAMPLE_IS_8}
const
CONST_BITS = 13;
PASS1_BITS = 2;
{$else}
const
CONST_BITS = 13;
PASS1_BITS = 1; { lose a little precision to avoid overflow }
{$endif}
const
FIX_0_211164243 = INT32(Round((INT32(1) shl CONST_BITS) * 0.211164243)); {1730}
FIX_0_509795579 = INT32(Round((INT32(1) shl CONST_BITS) * 0.509795579)); {4176}
FIX_0_601344887 = INT32(Round((INT32(1) shl CONST_BITS) * 0.601344887)); {4926}
FIX_0_720959822 = INT32(Round((INT32(1) shl CONST_BITS) * 0.720959822)); {5906}
FIX_0_765366865 = INT32(Round((INT32(1) shl CONST_BITS) * 0.765366865)); {6270}
FIX_0_850430095 = INT32(Round((INT32(1) shl CONST_BITS) * 0.850430095)); {6967}
FIX_0_899976223 = INT32(Round((INT32(1) shl CONST_BITS) * 0.899976223)); {7373}
FIX_1_061594337 = INT32(Round((INT32(1) shl CONST_BITS) * 1.061594337)); {8697}
FIX_1_272758580 = INT32(Round((INT32(1) shl CONST_BITS) * 1.272758580)); {10426}
FIX_1_451774981 = INT32(Round((INT32(1) shl CONST_BITS) * 1.451774981)); {11893}
FIX_1_847759065 = INT32(Round((INT32(1) shl CONST_BITS) * 1.847759065)); {15137}
FIX_2_172734803 = INT32(Round((INT32(1) shl CONST_BITS) * 2.172734803)); {17799}
FIX_2_562915447 = INT32(Round((INT32(1) shl CONST_BITS) * 2.562915447)); {20995}
FIX_3_624509785 = INT32(Round((INT32(1) shl CONST_BITS) * 3.624509785)); {29692}
{ Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
For 8-bit samples with the recommended scaling, all the variable
and constant values involved are no more than 16 bits wide, so a
16x16->32 bit multiply can be used instead of a full 32x32 multiply.
For 12-bit samples, a full 32-bit multiplication will be needed. }
{$ifdef BITS_IN_JSAMPLE_IS_8}
{function Multiply(X, Y: Integer): integer; assembler;
asm
mov ax, X
imul Y
mov al, ah
mov ah, dl
end;}
{MULTIPLY16C16(var,const)}
function Multiply(X, Y: Integer): INT32;
begin
Multiply := X*INT32(Y);
end;
{$else}
function Multiply(X, Y: INT32): INT32;
begin
Multiply := X*Y;
end;
{$endif}
{ Dequantize a coefficient by multiplying it by the multiplier-table
entry; produce an int result. In this module, both inputs and result
are 16 bits or less, so either int or short multiply will work. }
function DEQUANTIZE(coef,quantval : int) : int;
begin
Dequantize := ( ISLOW_MULT_TYPE(coef) * quantval);
end;
{ Descale and correctly round an INT32 value that's scaled by N bits.
We assume RIGHT_SHIFT rounds towards minus infinity, so adding
the fudge factor is correct for either sign of X. }
function DESCALE(x : INT32; n : int) : INT32;
var
shift_temp : INT32;
begin
{$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;
{ Perform dequantization and inverse DCT on one block of coefficients,
producing a reduced-size 4x4 output block. }
{GLOBAL}
procedure jpeg_idct_4x4 (cinfo : j_decompress_ptr;
compptr : jpeg_component_info_ptr;
coef_block : JCOEFPTR;
output_buf : JSAMPARRAY;
output_col : JDIMENSION);
type
PWorkspace = ^TWorkspace;
TWorkspace = array[0..(DCTSIZE*4)-1] of int; { buffers data between passes }
var
tmp0, tmp2, tmp10, tmp12 : INT32;
z1, z2, z3, z4 : INT32;
inptr : JCOEFPTR;
quantptr : ISLOW_MULT_TYPE_FIELD_PTR;
wsptr : PWorkspace;
outptr : JSAMPROW;
range_limit : JSAMPROW;
ctr : int;
workspace : TWorkspace; { buffers data between passes }
{SHIFT_TEMPS}
var
dcval : int;
var
dcval_ : JSAMPLE;
begin
{ Each IDCT routine is responsible for range-limiting its results and
converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
be quite far out of range if the input data is corrupt, so a bulletproof
range-limiting step is required. We use a mask-and-table-lookup method
to do the combined operations quickly. See the comments with
prepare_range_limit_table (in jdmaster.c) for more info. }
range_limit := JSAMPROW(@(cinfo^.sample_range_limit^[CENTERJSAMPLE]));
{ Pass 1: process columns from input, store into work array. }
inptr := coef_block;
quantptr := ISLOW_MULT_TYPE_FIELD_PTR (compptr^.dct_table);
wsptr := @workspace;
for ctr := DCTSIZE downto 1 do
begin
{ Don't bother to process column 4, because second pass won't use it }
if (ctr = DCTSIZE-4) then
begin
Inc(JCOEF_PTR(inptr));
Inc(ISLOW_MULT_TYPE_PTR(quantptr));
Inc(int_ptr(wsptr));
continue;
end;
if (inptr^[DCTSIZE*1]=0) and (inptr^[DCTSIZE*2]=0) and (inptr^[DCTSIZE*3]=0) and
(inptr^[DCTSIZE*5]=0) and (inptr^[DCTSIZE*6]=0) and (inptr^[DCTSIZE*7]=0) then
begin
{ AC terms all zero; we need not examine term 4 for 4x4 output }
dcval := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*0]) *
quantptr^[DCTSIZE*0]) shl PASS1_BITS;
wsptr^[DCTSIZE*0] := dcval;
wsptr^[DCTSIZE*1] := dcval;
wsptr^[DCTSIZE*2] := dcval;
wsptr^[DCTSIZE*3] := dcval;
Inc(JCOEF_PTR(inptr));
Inc(ISLOW_MULT_TYPE_PTR(quantptr));
Inc(int_ptr(wsptr));
continue;
end;
{ Even part }
tmp0 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*0]) * quantptr^[DCTSIZE*0]);
tmp0 := tmp0 shl (CONST_BITS+1);
z2 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*2]) * quantptr^[DCTSIZE*2]);
z3 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*6]) * quantptr^[DCTSIZE*6]);
tmp2 := MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
tmp10 := tmp0 + tmp2;
tmp12 := tmp0 - tmp2;
{ Odd part }
z1 := ISLOW_MULT_TYPE(inptr^[DCTSIZE*7]) * quantptr^[DCTSIZE*7];
z2 := ISLOW_MULT_TYPE(inptr^[DCTSIZE*5]) * quantptr^[DCTSIZE*5];
z3 := ISLOW_MULT_TYPE(inptr^[DCTSIZE*3]) * quantptr^[DCTSIZE*3];
z4 := ISLOW_MULT_TYPE(inptr^[DCTSIZE*1]) * quantptr^[DCTSIZE*1];
tmp0 := MULTIPLY(z1, - FIX_0_211164243) { sqrt(2) * (c3-c1) }
+ MULTIPLY(z2, FIX_1_451774981) { sqrt(2) * (c3+c7) }
+ MULTIPLY(z3, - FIX_2_172734803) { sqrt(2) * (-c1-c5) }
+ MULTIPLY(z4, FIX_1_061594337); { sqrt(2) * (c5+c7) }
tmp2 := MULTIPLY(z1, - FIX_0_509795579) { sqrt(2) * (c7-c5) }
+ MULTIPLY(z2, - FIX_0_601344887) { sqrt(2) * (c5-c1) }
+ MULTIPLY(z3, FIX_0_899976223) { sqrt(2) * (c3-c7) }
+ MULTIPLY(z4, FIX_2_562915447); { sqrt(2) * (c1+c3) }
{ Final output stage }
wsptr^[DCTSIZE*0] := int(DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1));
wsptr^[DCTSIZE*3] := int(DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1));
wsptr^[DCTSIZE*1] := int(DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1));
wsptr^[DCTSIZE*2] := int(DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1));
Inc(JCOEF_PTR(inptr));
Inc(ISLOW_MULT_TYPE_PTR(quantptr));
Inc(int_ptr(wsptr));
end;
{ Pass 2: process 4 rows from work array, store into output array. }
wsptr := @workspace;
for ctr := 0 to pred(4) do
begin
outptr := JSAMPROW(@ output_buf^[ctr]^[output_col]);
{ It's not clear whether a zero row test is worthwhile here ... }
{$ifndef NO_ZERO_ROW_TEST}
if (wsptr^[1]=0) and (wsptr^[2]=0) and (wsptr^[3]=0) and
(wsptr^[5]=0) and (wsptr^[6]=0) and (wsptr^[7]=0) then
begin
{ AC terms all zero }
dcval_ := range_limit^[int(DESCALE(INT32(wsptr^[0]), PASS1_BITS+3))
and RANGE_MASK];
outptr^[0] := dcval_;
outptr^[1] := dcval_;
outptr^[2] := dcval_;
outptr^[3] := dcval_;
Inc(int_ptr(wsptr), DCTSIZE); { advance pointer to next row }
continue;
end;
{$endif}
{ Even part }
tmp0 := (INT32(wsptr^[0])) shl (CONST_BITS+1);
tmp2 := MULTIPLY(INT32(wsptr^[2]), FIX_1_847759065)
+ MULTIPLY(INT32(wsptr^[6]), - FIX_0_765366865);
tmp10 := tmp0 + tmp2;
tmp12 := tmp0 - tmp2;
{ Odd part }
z1 := INT32(wsptr^[7]);
z2 := INT32(wsptr^[5]);
z3 := INT32(wsptr^[3]);
z4 := INT32(wsptr^[1]);
tmp0 := MULTIPLY(z1, - FIX_0_211164243) { sqrt(2) * (c3-c1) }
+ MULTIPLY(z2, FIX_1_451774981) { sqrt(2) * (c3+c7) }
+ MULTIPLY(z3, - FIX_2_172734803) { sqrt(2) * (-c1-c5) }
+ MULTIPLY(z4, FIX_1_061594337); { sqrt(2) * (c5+c7) }
tmp2 := MULTIPLY(z1, - FIX_0_509795579) { sqrt(2) * (c7-c5) }
+ MULTIPLY(z2, - FIX_0_601344887) { sqrt(2) * (c5-c1) }
+ MULTIPLY(z3, FIX_0_899976223) { sqrt(2) * (c3-c7) }
+ MULTIPLY(z4, FIX_2_562915447); { sqrt(2) * (c1+c3) }
{ Final output stage }
outptr^[0] := range_limit^[ int(DESCALE(tmp10 + tmp2,
CONST_BITS+PASS1_BITS+3+1))
and RANGE_MASK];
outptr^[3] := range_limit^[ int(DESCALE(tmp10 - tmp2,
CONST_BITS+PASS1_BITS+3+1))
and RANGE_MASK];
outptr^[1] := range_limit^[ int(DESCALE(tmp12 + tmp0,
CONST_BITS+PASS1_BITS+3+1))
and RANGE_MASK];
outptr^[2] := range_limit^[ int(DESCALE(tmp12 - tmp0,
CONST_BITS+PASS1_BITS+3+1))
and RANGE_MASK];
Inc(int_ptr(wsptr), DCTSIZE); { advance pointer to next row }
end;
end;
{ Perform dequantization and inverse DCT on one block of coefficients,
producing a reduced-size 2x2 output block. }
{GLOBAL}
procedure jpeg_idct_2x2 (cinfo : j_decompress_ptr;
compptr : jpeg_component_info_ptr;
coef_block : JCOEFPTR;
output_buf : JSAMPARRAY;
output_col : JDIMENSION);
type
PWorkspace = ^TWorkspace;
TWorkspace = array[0..(DCTSIZE*2)-1] of int; { buffers data between passes }
var
tmp0, tmp10, z1 : INT32;
inptr : JCOEFPTR;
quantptr : ISLOW_MULT_TYPE_FIELD_PTR;
wsptr : PWorkspace;
outptr : JSAMPROW;
range_limit : JSAMPROW;
ctr : int;
workspace : TWorkspace; { buffers data between passes }
{SHIFT_TEMPS}
var
dcval : int;
var
dcval_ : JSAMPLE;
begin
{ Each IDCT routine is responsible for range-limiting its results and
converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
be quite far out of range if the input data is corrupt, so a bulletproof
range-limiting step is required. We use a mask-and-table-lookup method
to do the combined operations quickly. See the comments with
prepare_range_limit_table (in jdmaster.c) for more info. }
range_limit := JSAMPROW(@(cinfo^.sample_range_limit^[CENTERJSAMPLE]));
{ Pass 1: process columns from input, store into work array. }
inptr := coef_block;
quantptr := ISLOW_MULT_TYPE_FIELD_PTR (compptr^.dct_table);
wsptr := @workspace;
for ctr := DCTSIZE downto 1 do
begin
{ Don't bother to process columns 2,4,6 }
if (ctr = DCTSIZE-2) or (ctr = DCTSIZE-4) or (ctr = DCTSIZE-6) then
begin
Inc(JCOEF_PTR(inptr));
Inc(ISLOW_MULT_TYPE_PTR(quantptr));
Inc(int_ptr(wsptr));
continue;
end;
if (inptr^[DCTSIZE*1]=0) and (inptr^[DCTSIZE*3]=0) and
(inptr^[DCTSIZE*5]=0) and (inptr^[DCTSIZE*7]=0) then
begin
{ AC terms all zero; we need not examine terms 2,4,6 for 2x2 output }
dcval := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*0]) *
quantptr^[DCTSIZE*0]) shl PASS1_BITS;
wsptr^[DCTSIZE*0] := dcval;
wsptr^[DCTSIZE*1] := dcval;
Inc(JCOEF_PTR(inptr));
Inc(ISLOW_MULT_TYPE_PTR(quantptr));
Inc(int_ptr(wsptr));
continue;
end;
{ Even part }
z1 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*0]) * quantptr^[DCTSIZE*0]);
tmp10 := z1 shl (CONST_BITS+2);
{ Odd part }
z1 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*7]) * quantptr^[DCTSIZE*7]);
tmp0 := MULTIPLY(z1, - FIX_0_720959822); { sqrt(2) * (c7-c5+c3-c1) }
z1 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*5]) * quantptr^[DCTSIZE*5]);
Inc(tmp0, MULTIPLY(z1, FIX_0_850430095)); { sqrt(2) * (-c1+c3+c5+c7) }
z1 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*3]) * quantptr^[DCTSIZE*3]);
Inc(tmp0, MULTIPLY(z1, - FIX_1_272758580)); { sqrt(2) * (-c1+c3-c5-c7) }
z1 := (ISLOW_MULT_TYPE(inptr^[DCTSIZE*1]) * quantptr^[DCTSIZE*1]);
Inc(tmp0, MULTIPLY(z1, FIX_3_624509785)); { sqrt(2) * (c1+c3+c5+c7) }
{ Final output stage }
wsptr^[DCTSIZE*0] := int (DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2));
wsptr^[DCTSIZE*1] := int (DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2));
Inc(JCOEF_PTR(inptr));
Inc(ISLOW_MULT_TYPE_PTR(quantptr));
Inc(int_ptr(wsptr));
end;
{ Pass 2: process 2 rows from work array, store into output array. }
wsptr := @workspace;
for ctr := 0 to pred(2) do
begin
outptr := JSAMPROW(@ output_buf^[ctr]^[output_col]);
{ It's not clear whether a zero row test is worthwhile here ... }
{$ifndef NO_ZERO_ROW_TEST}
if (wsptr^[1]=0) and (wsptr^[3]=0) and (wsptr^[5]=0) and (wsptr^[7]= 0) then
begin
{ AC terms all zero }
dcval_ := range_limit^[ int(DESCALE(INT32(wsptr^[0]), PASS1_BITS+3))
and RANGE_MASK];
outptr^[0] := dcval_;
outptr^[1] := dcval_;
Inc(int_ptr(wsptr), DCTSIZE); { advance pointer to next row }
continue;
end;
{$endif}
{ Even part }
tmp10 := (INT32 (wsptr^[0])) shl (CONST_BITS+2);
{ Odd part }
tmp0 := MULTIPLY( INT32(wsptr^[7]), - FIX_0_720959822) { sqrt(2) * (c7-c5+c3-c1) }
+ MULTIPLY( INT32(wsptr^[5]), FIX_0_850430095) { sqrt(2) * (-c1+c3+c5+c7) }
+ MULTIPLY( INT32(wsptr^[3]), - FIX_1_272758580) { sqrt(2) * (-c1+c3-c5-c7) }
+ MULTIPLY( INT32(wsptr^[1]), FIX_3_624509785); { sqrt(2) * (c1+c3+c5+c7) }
{ Final output stage }
outptr^[0] := range_limit^[ int(DESCALE(tmp10 + tmp0,
CONST_BITS+PASS1_BITS+3+2))
and RANGE_MASK];
outptr^[1] := range_limit^[ int(DESCALE(tmp10 - tmp0,
CONST_BITS+PASS1_BITS+3+2))
and RANGE_MASK];
Inc(int_ptr(wsptr), DCTSIZE); { advance pointer to next row }
end;
end;
{ Perform dequantization and inverse DCT on one block of coefficients,
producing a reduced-size 1x1 output block. }
{GLOBAL}
procedure jpeg_idct_1x1 (cinfo : j_decompress_ptr;
compptr : jpeg_component_info_ptr;
coef_block : JCOEFPTR;
output_buf : JSAMPARRAY;
output_col : JDIMENSION);
var
dcval : int;
quantptr : ISLOW_MULT_TYPE_FIELD_PTR;
range_limit : JSAMPROW;
{SHIFT_TEMPS}
begin
{ Each IDCT routine is responsible for range-limiting its results and
converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
be quite far out of range if the input data is corrupt, so a bulletproof
range-limiting step is required. We use a mask-and-table-lookup method
to do the combined operations quickly. See the comments with
prepare_range_limit_table (in jdmaster.c) for more info. }
range_limit := JSAMPROW(@(cinfo^.sample_range_limit^[CENTERJSAMPLE]));
{ Pass 1: process columns from input, store into work array. }
{ We hardly need an inverse DCT routine for this: just take the
average pixel value, which is one-eighth of the DC coefficient. }
quantptr := ISLOW_MULT_TYPE_FIELD_PTR (compptr^.dct_table);
dcval := (ISLOW_MULT_TYPE(coef_block^[0]) * quantptr^[0]);
dcval := int (DESCALE( INT32(dcval), 3));
output_buf^[0]^[output_col] := range_limit^[dcval and RANGE_MASK];
end;
end.
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