514 lines
16 KiB
Plaintext
514 lines
16 KiB
Plaintext
unit imjcdctmgr;
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{ Original : jcdctmgr.c ; Copyright (C) 1994-1996, Thomas G. Lane. }
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{ This file is part of the Independent JPEG Group's software.
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For conditions of distribution and use, see the accompanying README file.
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This file contains the forward-DCT management logic.
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This code selects a particular DCT implementation to be used,
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and it performs related housekeeping chores including coefficient
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quantization. }
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interface
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{$I imjconfig.inc}
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uses
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imjmorecfg,
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imjinclude,
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imjdeferr,
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imjerror,
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imjpeglib,
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imjdct, { Private declarations for DCT subsystem }
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imjfdctint, imjfdctfst, imjfdctflt;
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{ Initialize FDCT manager. }
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{GLOBAL}
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procedure jinit_forward_dct (cinfo : j_compress_ptr);
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implementation
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{ Private subobject for this module }
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type
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my_fdct_ptr = ^my_fdct_controller;
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my_fdct_controller = record
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pub : jpeg_forward_dct; { public fields }
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{ Pointer to the DCT routine actually in use }
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do_dct : forward_DCT_method_ptr;
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{ The actual post-DCT divisors --- not identical to the quant table
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entries, because of scaling (especially for an unnormalized DCT).
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Each table is given in normal array order. }
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divisors : array[0..NUM_QUANT_TBLS-1] of DCTELEM_FIELD_PTR;
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{$ifdef DCT_FLOAT_SUPPORTED}
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{ Same as above for the floating-point case. }
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do_float_dct : float_DCT_method_ptr;
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float_divisors : array[0..NUM_QUANT_TBLS-1] of FAST_FLOAT_FIELD_PTR;
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{$endif}
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end;
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{ Initialize for a processing pass.
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Verify that all referenced Q-tables are present, and set up
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the divisor table for each one.
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In the current implementation, DCT of all components is done during
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the first pass, even if only some components will be output in the
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first scan. Hence all components should be examined here. }
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{METHODDEF}
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procedure start_pass_fdctmgr (cinfo : j_compress_ptr);
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var
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fdct : my_fdct_ptr;
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ci, qtblno, i : int;
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compptr : jpeg_component_info_ptr;
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qtbl : JQUANT_TBL_PTR;
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dtbl : DCTELEM_FIELD_PTR;
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{$ifdef DCT_IFAST_SUPPORTED}
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const
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CONST_BITS = 14;
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aanscales : array[0..DCTSIZE2-1] of INT16 =
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({ precomputed values scaled up by 14 bits }
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16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
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22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
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21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
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19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
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16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
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12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
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8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
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4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247);
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{SHIFT_TEMPS}
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{ Descale and correctly round an INT32 value that's scaled by N bits.
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We assume RIGHT_SHIFT rounds towards minus infinity, so adding
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the fudge factor is correct for either sign of X. }
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function DESCALE(x : INT32; n : int) : INT32;
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var
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shift_temp : INT32;
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begin
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shift_temp := x + (INT32(1) shl (n-1));
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{$ifdef RIGHT_SHIFT_IS_UNSIGNED}
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if shift_temp < 0 then
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Descale := (shift_temp shr n) or ((not INT32(0)) shl (32-n))
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else
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{$endif}
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Descale := (shift_temp shr n);
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end;
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{$endif}
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{$ifdef DCT_FLOAT_SUPPORTED}
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var
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fdtbl : FAST_FLOAT_FIELD_PTR;
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row, col : int;
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const
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aanscalefactor : array[0..DCTSIZE-1] of double =
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(1.0, 1.387039845, 1.306562965, 1.175875602,
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1.0, 0.785694958, 0.541196100, 0.275899379);
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{$endif}
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begin
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fdct := my_fdct_ptr (cinfo^.fdct);
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compptr := jpeg_component_info_ptr(cinfo^.comp_info);
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for ci := 0 to pred(cinfo^.num_components) do
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begin
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qtblno := compptr^.quant_tbl_no;
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{ Make sure specified quantization table is present }
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if (qtblno < 0) or (qtblno >= NUM_QUANT_TBLS) or
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(cinfo^.quant_tbl_ptrs[qtblno] = NIL) then
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ERREXIT1(j_common_ptr(cinfo), JERR_NO_QUANT_TABLE, qtblno);
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qtbl := cinfo^.quant_tbl_ptrs[qtblno];
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{ Compute divisors for this quant table }
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{ We may do this more than once for same table, but it's not a big deal }
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case (cinfo^.dct_method) of
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{$ifdef DCT_ISLOW_SUPPORTED}
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JDCT_ISLOW:
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begin
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{ For LL&M IDCT method, divisors are equal to raw quantization
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coefficients multiplied by 8 (to counteract scaling). }
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if (fdct^.divisors[qtblno] = NIL) then
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begin
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fdct^.divisors[qtblno] := DCTELEM_FIELD_PTR(
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cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
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DCTSIZE2 * SIZEOF(DCTELEM)) );
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end;
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dtbl := fdct^.divisors[qtblno];
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for i := 0 to pred(DCTSIZE2) do
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begin
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dtbl^[i] := (DCTELEM(qtbl^.quantval[i])) shl 3;
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end;
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end;
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{$endif}
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{$ifdef DCT_IFAST_SUPPORTED}
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JDCT_IFAST:
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begin
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{ For AA&N IDCT method, divisors are equal to quantization
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coefficients scaled by scalefactor[row]*scalefactor[col], where
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scalefactor[0] := 1
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scalefactor[k] := cos(k*PI/16) * sqrt(2) for k=1..7
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We apply a further scale factor of 8. }
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if (fdct^.divisors[qtblno] = NIL) then
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begin
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fdct^.divisors[qtblno] := DCTELEM_FIELD_PTR(
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cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
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DCTSIZE2 * SIZEOF(DCTELEM)) );
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end;
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dtbl := fdct^.divisors[qtblno];
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for i := 0 to pred(DCTSIZE2) do
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begin
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dtbl^[i] := DCTELEM(
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{MULTIPLY16V16}
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DESCALE( INT32(qtbl^.quantval[i]) * INT32 (aanscales[i]),
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CONST_BITS-3) );
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end;
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end;
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{$endif}
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{$ifdef DCT_FLOAT_SUPPORTED}
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JDCT_FLOAT:
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begin
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{ For float AA&N IDCT method, divisors are equal to quantization
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coefficients scaled by scalefactor[row]*scalefactor[col], where
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scalefactor[0] := 1
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scalefactor[k] := cos(k*PI/16) * sqrt(2) for k=1..7
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We apply a further scale factor of 8.
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What's actually stored is 1/divisor so that the inner loop can
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use a multiplication rather than a division. }
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if (fdct^.float_divisors[qtblno] = NIL) then
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begin
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fdct^.float_divisors[qtblno] := FAST_FLOAT_FIELD_PTR(
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cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
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DCTSIZE2 * SIZEOF(FAST_FLOAT)) );
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end;
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fdtbl := fdct^.float_divisors[qtblno];
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i := 0;
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for row := 0 to pred(DCTSIZE) do
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begin
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for col := 0 to pred(DCTSIZE) do
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begin
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fdtbl^[i] := {FAST_FLOAT}
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(1.0 / (( {double}(qtbl^.quantval[i]) *
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aanscalefactor[row] * aanscalefactor[col] * 8.0)));
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Inc(i);
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end;
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end;
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end;
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{$endif}
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else
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ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
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end;
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Inc(compptr);
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end;
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end;
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{ Perform forward DCT on one or more blocks of a component.
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The input samples are taken from the sample_data[] array starting at
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position start_row/start_col, and moving to the right for any additional
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blocks. The quantized coefficients are returned in coef_blocks[]. }
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{METHODDEF}
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procedure forward_DCT (cinfo : j_compress_ptr;
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compptr : jpeg_component_info_ptr;
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sample_data : JSAMPARRAY;
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coef_blocks : JBLOCKROW;
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start_row : JDIMENSION;
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start_col : JDIMENSION;
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num_blocks : JDIMENSION);
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{ This version is used for integer DCT implementations. }
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var
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{ This routine is heavily used, so it's worth coding it tightly. }
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fdct : my_fdct_ptr;
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do_dct : forward_DCT_method_ptr;
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divisors : DCTELEM_FIELD_PTR;
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workspace : array[0..DCTSIZE2-1] of DCTELEM; { work area for FDCT subroutine }
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bi : JDIMENSION;
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var
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{register} workspaceptr : DCTELEMPTR;
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{register} elemptr : JSAMPLE_PTR;
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{register} elemr : int;
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{$ifndef DCTSIZE_IS_8}
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var
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{register} elemc : int;
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{$endif}
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var
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{register} temp, qval : DCTELEM;
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{register} i : int;
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{register} output_ptr : JCOEFPTR;
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begin
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fdct := my_fdct_ptr (cinfo^.fdct);
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do_dct := fdct^.do_dct;
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divisors := fdct^.divisors[compptr^.quant_tbl_no];
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Inc(JSAMPROW_PTR(sample_data), start_row); { fold in the vertical offset once }
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for bi := 0 to pred(num_blocks) do
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begin
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{ Load data into workspace, applying unsigned->signed conversion }
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workspaceptr := @workspace[0];
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for elemr := 0 to pred(DCTSIZE) do
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begin
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elemptr := @sample_data^[elemr]^[start_col];
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{$ifdef DCTSIZE_IS_8} { unroll the inner loop }
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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{Inc(elemptr); - Value never used }
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{$else}
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for elemc := pred(DCTSIZE) downto 0 do
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begin
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workspaceptr^ := GETJSAMPLE(elemptr^) - CENTERJSAMPLE;
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Inc(workspaceptr);
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Inc(elemptr);
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end;
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{$endif}
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end;
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{ Perform the DCT }
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do_dct (workspace);
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{ Quantize/descale the coefficients, and store into coef_blocks[] }
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output_ptr := JCOEFPTR(@coef_blocks^[bi]);
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for i := 0 to pred(DCTSIZE2) do
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begin
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qval := divisors^[i];
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temp := workspace[i];
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{ Divide the coefficient value by qval, ensuring proper rounding.
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Since C does not specify the direction of rounding for negative
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quotients, we have to force the dividend positive for portability.
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In most files, at least half of the output values will be zero
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(at default quantization settings, more like three-quarters...)
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so we should ensure that this case is fast. On many machines,
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a comparison is enough cheaper than a divide to make a special test
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a win. Since both inputs will be nonnegative, we need only test
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for a < b to discover whether a/b is 0.
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If your machine's division is fast enough, define FAST_DIVIDE. }
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if (temp < 0) then
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begin
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temp := -temp;
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Inc(temp, qval shr 1); { for rounding }
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{DIVIDE_BY(temp, qval);}
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{$ifdef FAST_DIVIDE}
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temp := temp div qval;
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{$else}
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if (temp >= qval) then
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temp := temp div qval
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else
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temp := 0;
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{$endif}
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temp := -temp;
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end
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else
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begin
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Inc(temp, qval shr 1); { for rounding }
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{DIVIDE_BY(temp, qval);}
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{$ifdef FAST_DIVIDE}
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temp := temp div qval;
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{$else}
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if (temp >= qval) then
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temp := temp div qval
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else
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temp := 0;
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{$endif}
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end;
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output_ptr^[i] := JCOEF (temp);
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end;
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Inc(start_col, DCTSIZE);
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end;
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end;
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{$ifdef DCT_FLOAT_SUPPORTED}
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{METHODDEF}
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procedure forward_DCT_float (cinfo : j_compress_ptr;
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compptr : jpeg_component_info_ptr;
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sample_data : JSAMPARRAY;
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coef_blocks : JBLOCKROW;
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start_row : JDIMENSION;
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start_col : JDIMENSION;
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num_blocks : JDIMENSION);
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{ This version is used for floating-point DCT implementations. }
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var
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{ This routine is heavily used, so it's worth coding it tightly. }
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fdct : my_fdct_ptr;
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do_dct : float_DCT_method_ptr;
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divisors : FAST_FLOAT_FIELD_PTR;
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workspace : array[0..DCTSIZE2-1] of FAST_FLOAT; { work area for FDCT subroutine }
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bi : JDIMENSION;
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var
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{register} workspaceptr : FAST_FLOAT_PTR;
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{register} elemptr : JSAMPLE_PTR;
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{register} elemr : int;
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{$ifndef DCTSIZE_IS_8}
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var
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{register} elemc : int;
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{$endif}
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var
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{register} temp : FAST_FLOAT;
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{register} i : int;
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{register} output_ptr : JCOEFPTR;
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begin
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fdct := my_fdct_ptr (cinfo^.fdct);
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do_dct := fdct^.do_float_dct;
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divisors := fdct^.float_divisors[compptr^.quant_tbl_no];
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Inc(JSAMPROW_PTR(sample_data), start_row); { fold in the vertical offset once }
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for bi := 0 to pred(num_blocks) do
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begin
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{ Load data into workspace, applying unsigned->signed conversion }
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workspaceptr := @workspace[0];
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for elemr := 0 to pred(DCTSIZE) do
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begin
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elemptr := @(sample_data^[elemr]^[start_col]);
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{$ifdef DCTSIZE_IS_8} { unroll the inner loop }
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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Inc(elemptr);
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workspaceptr^ := {FAST_FLOAT}(GETJSAMPLE(elemptr^) - CENTERJSAMPLE);
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Inc(workspaceptr);
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{Inc(elemptr); - value never used }
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{$else}
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for elemc := pred(DCTSIZE) downto 0 do
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begin
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workspaceptr^ := {FAST_FLOAT}(
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(GETJSAMPLE(elemptr^) - CENTERJSAMPLE) );
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Inc(workspaceptr);
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Inc(elemptr);
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end;
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{$endif}
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end;
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{ Perform the DCT }
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do_dct (workspace);
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{ Quantize/descale the coefficients, and store into coef_blocks[] }
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output_ptr := JCOEFPTR(@(coef_blocks^[bi]));
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for i := 0 to pred(DCTSIZE2) do
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begin
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{ Apply the quantization and scaling factor }
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temp := workspace[i] * divisors^[i];
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{ Round to nearest integer.
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Since C does not specify the direction of rounding for negative
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quotients, we have to force the dividend positive for portability.
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The maximum coefficient size is +-16K (for 12-bit data), so this
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code should work for either 16-bit or 32-bit ints. }
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output_ptr^[i] := JCOEF ( int(Trunc (temp + {FAST_FLOAT}(16384.5))) - 16384);
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end;
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Inc(start_col, DCTSIZE);
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end;
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end;
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{$endif} { DCT_FLOAT_SUPPORTED }
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{ Initialize FDCT manager. }
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{GLOBAL}
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procedure jinit_forward_dct (cinfo : j_compress_ptr);
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var
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fdct : my_fdct_ptr;
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i : int;
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begin
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fdct := my_fdct_ptr(
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cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
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SIZEOF(my_fdct_controller)) );
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cinfo^.fdct := jpeg_forward_dct_ptr (fdct);
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fdct^.pub.start_pass := start_pass_fdctmgr;
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case (cinfo^.dct_method) of
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{$ifdef DCT_ISLOW_SUPPORTED}
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JDCT_ISLOW:
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begin
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fdct^.pub.forward_DCT := forward_DCT;
|
|
fdct^.do_dct := jpeg_fdct_islow;
|
|
end;
|
|
{$endif}
|
|
{$ifdef DCT_IFAST_SUPPORTED}
|
|
JDCT_IFAST:
|
|
begin
|
|
fdct^.pub.forward_DCT := forward_DCT;
|
|
fdct^.do_dct := jpeg_fdct_ifast;
|
|
end;
|
|
{$endif}
|
|
{$ifdef DCT_FLOAT_SUPPORTED}
|
|
JDCT_FLOAT:
|
|
begin
|
|
fdct^.pub.forward_DCT := forward_DCT_float;
|
|
fdct^.do_float_dct := jpeg_fdct_float;
|
|
end;
|
|
{$endif}
|
|
else
|
|
ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
|
|
end;
|
|
|
|
{ Mark divisor tables unallocated }
|
|
for i := 0 to pred(NUM_QUANT_TBLS) do
|
|
begin
|
|
fdct^.divisors[i] := NIL;
|
|
{$ifdef DCT_FLOAT_SUPPORTED}
|
|
fdct^.float_divisors[i] := NIL;
|
|
{$endif}
|
|
end;
|
|
end;
|
|
|
|
end.
|